Each capsule contains: Vitamin C (as ascorbic acid) 1000 mg • Citrus Bioflavonoids 100 mg, providing Lemon Bioflavonoids 60 mg, Orange Bioflavonoids 15 mg, Grapefruit Bioflavonoids 15 mg, Hesperidin 3 mg • Rutin 50 mg. Other Ingredients: Cellulose, Gelatin (capsule shell), Stearic Acid, Magnesium Stearate, Silica, Calcium Silicate.
Brand name products often contain multiple ingredients. To read detailed information about each ingredient, click on the link for the individual ingredient shown above.
Below is general information about the effectiveness of the known ingredients contained in the product Hypoallergenic Maxi C Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
INSUFFICIENT RELIABLE EVIDENCE to RATE
INSUFFICIENT RELIABLE EVIDENCE to RATE
INSUFFICIENT RELIABLE EVIDENCE to RATE
INSUFFICIENT RELIABLE EVIDENCE to RATE
INSUFFICIENT RELIABLE EVIDENCE to RATE
INSUFFICIENT RELIABLE EVIDENCE to RATE
INSUFFICIENT RELIABLE EVIDENCE to RATE
Below is general information about the safety of the known ingredients contained in the product Hypoallergenic Maxi C Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
LIKELY SAFE ...when used orally in amounts found in foods.
POSSIBLY SAFE ...when supplements are used orally and appropriately, short-term. Diosmin seems to be safe when used alone or in combination with other flavonoids in doses of up to 1350 mg daily for up to 6 months (4861,4898,10227,10229,93885,105283,105286,105287,105293,105294)(105296,108150).
PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts found in foods.
PREGNANCY AND LACTATION: POSSIBLY SAFE
when used orally in doses of up to 900 mg daily for 30 days in combination with other flavonoids, such as hesperidin.
Some evidence suggests that taking this combination may be associated with placental insufficiency when used during the third trimester of pregnancy; however, the combination does not seem to induce fetal abnormalities, retard fetal growth, increase the risk of intrauterine death, or affect birth weight. Also, when breastfeeding, this combination does not seem to affect infant growth or feeding (54970).
LIKELY SAFE ...when used orally in amounts commonly found in foods. Grapefruit has Generally Recognized as Safe status (GRAS) in the US (4912).
POSSIBLY SAFE ...when used orally and appropriately for medicinal purposes. A grapefruit seed extract has been safely used in clinical research (5866). In addition, capsules containing grapefruit pectin 15 grams daily have been used in clinical research for up to 16 weeks (2216).
POSSIBLY UNSAFE ...when used orally in excessive amounts. Preliminary population research shows that consuming a quarter or more of a whole grapefruit daily is associated with a 25% to 30% increased risk of postmenopausal breast cancer (14858). Grapefruit juice is thought to reduce estrogen metabolism resulting in increased endogenous estrogen levels. More evidence is needed to validate this finding.
PREGNANCY AND LACTATION:
There is insufficient reliable information available about the safety of using medicinal amounts of grapefruit during pregnancy and lactation; avoid using.
LIKELY SAFE ...when used orally in amounts found in foods.
POSSIBLY SAFE ...when supplements are used orally and appropriately, short-term. Doses of up to 3 grams daily have been used with apparent safety for up to 3 months (37494,54850,94544,105275,105276).
PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts found in foods.
PREGNANCY AND LACTATION: POSSIBLY SAFE
when used orally in doses of up to 100 mg daily for 30 days in combination with diosmin.
Some evidence suggests that taking this combination may be associated with placental insufficiency when used during the third trimester of pregnancy; however, the combination does not seem to induce fetal abnormalities, retard fetal growth, increase the risk of intrauterine death, or affect birth weight. Also, when breastfeeding, this combination does not seem to affect infant growth or feeding (54970).
LIKELY SAFE ...when used in amounts commonly found in foods. Lemon has Generally Recognized as Safe (GRAS) status in the US (4912).
POSSIBLY SAFE ...when inhaled in amounts used for aromatherapy, short-term. Lemon essential oil has been used with apparent safety as aromatherapy for up to 2 weeks in clinical research (93475,98128,98129). There is insufficient reliable information available about the safety of lemon when used topically, or when used orally or intranasally in medicinal amounts.
PREGNANCY AND LACTATION:
Insufficient reliable information available.
Avoid using in amounts greater than those typically found in foods.
LIKELY SAFE ...when used orally in amounts found in foods, such as fruits and vegetables.
POSSIBLY SAFE ...when used orally in medicinal amounts, short-term. Rutin has been used with apparent safety at doses of up to 600 mg daily for up to 12 weeks (6252,24560,91104,96766,105298). ...when applied topically as a cream (92236,99258,99260).
PREGNANCY AND LACTATION: LIKELY SAFE
when used orally in amounts commonly found in foods.
There is insufficient reliable information available about the use of supplemental rutin; avoid amounts greater than those found in foods.
LIKELY SAFE ...when sweet orange juice or fruit is used orally in amounts commonly found in foods (1310,3340,15171,92309,114401).
POSSIBLY SAFE ...when the essential oil of sweet orange is inhaled as aromatherapy, short-term (35735,58060,90505,105455). There is insufficient reliable information available about the safety of sweet orange peel when used orally.
CHILDREN: LIKELY SAFE
when sweet orange juice or fruit is used orally in amounts commonly found in foods.
CHILDREN: POSSIBLY UNSAFE
when the sweet orange peel is used orally in excessive amounts.
There have been reports of intestinal colic, convulsions, and death in children given large amounts of sweet orange peel (11).
PREGNANCY AND LACTATION: LIKELY SAFE
when sweet orange juice or fruit is used orally in amounts commonly found in foods (1310,3340).
LIKELY SAFE ...when used orally, topically, intramuscularly, or intravenously and appropriately. Vitamin C is safe when taken orally in doses below the tolerable upper intake level (UL). Tell patients not to exceed the UL of 2000 mg daily (1959,4713,4714,4844). ...when used intravenously or intramuscularly and appropriately. Injectable vitamin C is an FDA-approved prescription product (15) and has been used with apparent safety in clinical trials up to 150 mg/kg daily for up to 4 days (114489) and up to 200 mg/kg daily for up to 2 days (114492).
POSSIBLY UNSAFE ...when used orally in excessive doses. Doses greater than the tolerable upper intake level (UL) of 2000 mg daily can significantly increase the risk of adverse effects such as osmotic diarrhea and gastrointestinal upset (4844).
CHILDREN: LIKELY SAFE
when used orally and appropriately (4844,10352,14443).
CHILDREN: POSSIBLY UNSAFE
when used orally in excessive amounts.
Tell patients not to use doses above the tolerable upper intake level (UL) of 400 mg daily for children ages 1 to 3 years, 650 mg daily for children 4 to 8 years, 1200 mg daily for children 9 to 13 years, and 1800 mg daily for adolescents 14 to 18 years. Higher doses can cause osmotic diarrhea and gastrointestinal upset (4844).
PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately (4844).
PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when used orally in excessive doses.
Tell patients over age 19 not to use doses exceeding the UL of 2000 mg daily when pregnant or breast-feeding and for those 14-18 years of age not to use doses exceeding 1800 mg daily when pregnant or breast-feeding. Higher doses can cause osmotic diarrhea and gastrointestinal upset. Large doses of vitamin C during pregnancy can also cause newborn scurvy (4844); avoid using.
Below is general information about the interactions of the known ingredients contained in the product Hypoallergenic Maxi C Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
Theoretically, diosmin may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
 Details
A case of spontaneous intraventricular hemorrhage has been reported for a 77-year-old female after 6 weeks of warfarin therapy, despite an international normalized ratio (INR) of only 1.8. The patient had also been taking aspirin and diosmin for several years. Experts speculate that chronic intake of diosmin predisposed the patient to spontaneous intraventricular hemorrhage by inducing chronic microcirculatory hypertension and inhibiting platelet aggregation. The presence of aspirin was also thought to play a role in this event (93886).
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Theoretically, diosmin might reduce the effects of carbamazepine and increase the risk for convulsions.
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A pharmacokinetic study in humans shows that taking diosmin (Venex) 500 mg daily for 10 days prior to oral administration of carbamazepine 200 mg increases blood levels of carbamazepine by approximately 58% and decreases carbamazepine clearance by 42%. It also decreases the formation of carbamazepine's active metabolite. It is speculated that diosmin reduces the metabolism of carbamazepine by inhibiting cytochrome P450 3A4 (CYP3A4) (95041).
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Theoretically, diosmin might increase the levels and clinical effects of chlorzoxazone.
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A pharmacokinetic study in humans shows that taking diosmin (Venex 500) 500 mg daily for 9 days prior to oral administration of chlorzoxazone 250 mg increases blood levels of chlorzoxazone by 53% and decreases chlorzoxazone clearance by 40%. It is speculated that diosmin reduces the metabolism of chlorzoxazone by inhibiting cytochrome P450 2E1 (CYP2E1) (93889).
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Theoretically, diosmin might inhibit the metabolism of CYP2C9 substrates.
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Diclofenac is metabolized by CYP2C9 enzymes. Clinical and laboratory research shows that diosmin inhibits the metabolism of diclofenac (93888,98596). A pharmacokinetic study in humans shows that taking diosmin (Venex 500) 500 mg daily for 9 days prior to oral administration of diclofenac 100 mg increases blood levels of diclofenac and decreases diclofenac clearance (93888).
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Theoretically, diosmin might inhibit the metabolism of CYP2E1 substrates.
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Chlorzoxazone is metabolized by CYP2E1 enzymes. A pharmacokinetic study in humans shows that taking diosmin (Venex 500) 500 mg daily for 9 days prior to oral administration of chlorzoxazone (Paraflex 250) 250 mg increases blood levels of chlorzoxazone by 34% and decreases chlorzoxazone clearance by 40%. It is speculated that diosmin reduces the metabolism of chlorzoxazone by inhibiting CYP2E1 (93889).
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Theoretically, diosmin might inhibit the metabolism of CYP3A4 substrates.
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Laboratory research is conflicting with respect to the effects of diosmin on CYP3A4. Some research suggests that diosmin does not affect CYP3A4 activity (95040). However, other research suggests that diosmin alters the metabolism of carbamazepine, a CYP3A4 substrate. Laboratory and animal research show that oral administration of diosmin for 7 days prior to oral administration of carbamazepine increases plasma concentrations of carbamazepine, decreases the clearance of carbamazepine, and decreases the formation of carbamazepine's active metabolite (95039). Additionally, pharmacokinetic research in healthy male subjects shows that taking diosmin (Venex) 500 mg daily for 10 days prior to oral administration of carbamazepine 200 mg increases blood levels of carbamazepine by approximately 58% and decreases carbamazepine clearance by 42% (95041). It is speculated that diosmin reduces the metabolism of carbamazepine by inhibiting CYP3A4 (95039,95041). Diosmetin, a metabolite of diosmin, may also inhibit CYP3A4 (95041).
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Theoretically, diosmin might increase the levels and clinical effects of diclofenac.
Details
Clinical and laboratory research shows that diosmin inhibits the metabolism of diclofenac (93888,98596). A pharmacokinetic study in humans shows that taking diosmin (Venex 500) 500 mg daily for 9 days prior to oral administration of diclofenac 100 mg increases blood levels of diclofenac and decreases diclofenac clearance. It is speculated that diosmin reduces the metabolism of diclofenac by inhibiting cytochrome P450 2C9 (CYP2C9) (93888).
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Theoretically, diosmin might increase the levels and clinical effects of fexofenadine.
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A pharmacokinetic study in humans shows that taking diosmin (Venex) 500 mg daily for 10 days prior to oral administration of fexofenadine 120 mg increases blood levels of fexofenadine by approximately 49% and decreases the apparent oral clearance of fexofenadine by 41%. The time taken to reach maximum plasma concentration, the half-life, and the apparent renal clearance of fexofenadine are not affected. For this reason, it is speculated that diosmin alters the pharmacokinetics of fexofenadine via inhibition of P-glycoprotein in the intestine, but not in the kidney or liver (95042).
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Theoretically, diosmin might increase levels of drugs that are substrates of P-glycoprotein (P-gp).
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Preliminary laboratory research suggests that diosmin inhibits P-gp (93890). Additionally, pharmacokinetic research in healthy male subjects shows that taking diosmin (Venex) 500 mg daily for 10 days prior to oral administration of fexofenadine 120 mg increases blood levels of fexofenadine, a P-gp substrate, by approximately 49% and decreases the apparent oral clearance of fexofenadine by 41%. The time taken to reach maximum plasma concentration, the half-life, and the apparent renal clearance of fexofenadine are not affected. For this reason, it is speculated that diosmin inhibits P-gp in the intestine, but not in the kidney or liver (95042).
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Grapefruit juice can decrease blood levels of acebutolol, potentially decreasing the clinical effects of acebutolol.
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Clinical research shows that grapefruit juice can modestly decrease acebutolol levels by 7% and reduce peak plasma concentration by 19% by inhibiting organic anion transporting polypeptide (OATP) (17603,18101). The acebutolol half-life is also extended by 1.1 hours when grapefruit juice is consumed concomitantly (18101). Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction (17603,17604).
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Grapefruit juice can decrease blood levels of aliskiren, potentially decreasing the clinical effects of aliskiren.
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Clinical research shows that grapefruit juice can decrease aliskiren levels by approximately 60% by inhibiting organic anion transporting polypeptide (OATP) (91428). Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction (17603,17604).
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Grapefruit juice can increase blood levels of amiodarone, potentially increasing the effects and adverse effects of amiodarone.
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Grapefruit juice might decrease blood levels of amprenavir, although this is not likely to be clinically significant.
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Some clinical research shows that grapefruit juice can slightly decrease amprenavir levels (17673); however, this is probably not clinically significant.
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Grapefruit juice can increase blood levels of oral artemether, potentially increasing the effects and adverse effects of artemether.
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Grapefruit juice might increase blood levels of some oral benzodiazepines, potentially increasing the effects and adverse effects of these drugs.
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Clinical research shows that grapefruit juice can increase plasma triazolam concentrations. Repeated consumption of grapefruit juice greatly increases triazolam concentrations and prolongs the half-life, probably due to inhibition of cytochrome P450 3A4 (CYP3A4) (7776,22118,22131,22133). Some studies show that grapefruit juice, particularly when taken in large quantities, reduces the clearance and increases the maximum blood levels, area under the plasma concentration curve (AUC), and duration of effect of midazolam. However, there is no effect on intravenous midazolam (4300,10159,11275,17601,22117,22119,16711,91427,95978). Grapefruit juice has also been shown to increase the maximum blood levels and duration of effect of diazepam, but the clinical significance of this is not known (3228). This interaction does not appear to occur with alprazolam (17674).
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Grapefruit juice can increase blood levels of blonanserin, potentially increasing the effects and adverse effects of blonanserin.
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Blonanserin is metabolized primarily by cytochrome P450 3A4 (CYP3A4). A small clinical study shows that taking grapefruit juice along with oral blonanserin increases exposure to blonanserin almost 6-fold due to inhibition of intestinal CYP3A4 by grapefruit juice and prolongs the elimination half-life of blonanserin by 2.2-fold due to inhibition of hepatic CYP3A4 by grapefruit juice (96943).
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Grapefruit juice can increase blood levels of budesonide, potentially increasing the effects and adverse effects of budesonide.
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Budesonide is metabolized by cytochrome P450 3A4 (CYP3A4). A small clinical study shows that taking grapefruit juice along with oral budesonide increases the plasma concentration of budesonide. This effect is attributed to grapefruit-induced inhibition of CYP3A4 in both the colon and small intestine (91425).
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Grapefruit juice can increase blood levels of buspirone, potentially increasing the effects and adverse effects of buspirone.
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Clinical research shows that grapefruit juice increases absorption and plasma concentrations of buspirone (3771).
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Grapefruit juice can decrease the clearance of caffeine, potentially increasing the effects and adverse effects of caffeine.
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Clinical research shows that grapefruit juice decreases caffeine clearance (4300).
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Grapefruit juice can increase blood levels of oral calcium channel blockers, potentially increasing the effects and adverse effects of these drugs.
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Clinical research shows that grapefruit juice increases absorption and plasma concentrations of amlodipine (523), nifedipine (528,22114), nisoldipine (529), verapamil (7779,8285), felodipine, nimodipine, nicardipine, diltiazem, pranidipine, nitrendipine, and manidipine (524,528,1388,4300,7780,11276,22136,53338,22138,22139) (22140,22141,22142,22143,22147,22148,22149,53367,22158),
This interaction is likely the result of the inhibition of intestinal metabolism of these drugs by CYP3A4 (7779,7780), although some research suggests grapefruit may alter plasma drug levels by reducing the rate of gastric emptying (22167). Consuming grapefruit juice 1 liter daily increases steady state concentrations of verapamil by as much as 50% (8285). However, some references dispute the clinical relevance of the interactions with amlodipine, diltiazem, and verapamil (3230,4300,22159). Other research in healthy individuals suggests plasma levels of felodipine and nifedipine are not affected when given intravenously (22144,22146). There is considerable interindividual variability in the effect of grapefruit juice on drug metabolism, which might account for inconsistent study results (7777,7779,8285). In healthy older adults, the hemodynamic response to felodipine plus grapefruit juice might be influenced by altered autonomic regulation. In older healthy adults, a single dose of grapefruit juice and felodipine enhanced the blood pressure-lowering effects of felodipine. However, after a week of grapefruit juice and felodipine (steady state), the hypotensive activity was reduced, possibly due to compensatory tachycardia (1392). Research indicates it is necessary to withhold grapefruit juice for as long as 3 days to avoid interactions with felodipine and nisoldipine (5068,5069,6453,22145).
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Grapefruit juice can increase blood levels of carbamazepine, potentially increasing the effects and adverse effects of carbamazepine.
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Clinical research shows that grapefruit juice increases absorption and plasma concentrations of carbamazepine (524).
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Grapefruit juice can increase blood levels of carvedilol, potentially increasing the effects and adverse effects of carvedilol.
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Clinical research shows that grapefruit juice increases the bioavailability of a single dose of carvedilol by 16% (5071).
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Grapefruit juice can decrease blood levels of celiprolol, potentially decreasing the clinical effects of celiprolol.
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In human research, taking grapefruit juice within two hours of celiprolol appears to decrease absorption and blood levels of celiprolol by approximately 85% (91421). This interaction is due to grapefruit-induced inhibition of organic anion transporting polypeptide (OATP) (17603,17604,22161). Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction (17603,17604).
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Grapefruit juice can increase blood levels of cisapride, potentially increasing the effects and adverse effects of cisapride.
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Theoretically, grapefruit juice might increase blood levels of clomipramine, potentially increasing the effects and adverse effects of clomipramine.
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Case reports have shown that clomipramine trough levels increase significantly after the addition of grapefruit juice to the therapeutic regimen (5064).
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Grapefruit juice can decrease blood levels of the active metabolite of clopidogrel, thereby decreasing the antiplatelet effect of clopidogrel.
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Clopidogrel is an antiplatelet prodrug that is metabolized primarily by cytochrome P450 2C19 (CYP2C19) to form the active metabolite. A small clinical study shows that taking grapefruit juice with clopidogrel decreases plasma levels of the active metabolite by more than 80% and impairs the antiplatelet effect of clopidogrel. This effect is possibly due to grapefruit-induced inhibition of CYP2C19 (91419).
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Theoretically, grapefruit juice might increase blood levels of colchicine, potentially increasing the effects and adverse effects of colchicine.
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Colchicine is an alkaloid that undergoes P-glycoprotein (P-gp) mediated drug efflux in the intestines, followed by metabolism by cytochrome P450 3A4 (CYP3A4). There is concern that grapefruit juice will increase the effects and adverse effects of colchicine due to grapefruit-induced inhibition of P-gp and/or CYP3A4. In vitro evidence shows that grapefruit juice increases absorption of colchicine by inhibiting P-gp (94158). A case of acute colchicine toxicity has been reported for an 8-year-old female who drank grapefruit juice while taking high-dose colchicine, long-term (94157). However, one small clinical study in healthy adults shows that drinking grapefruit juice 240 mL twice daily for 4 days does not affect the bioavailability or adverse effects of a single dose of colchicine 0.6 mg taken on the fourth day (35762).
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Grapefruit juice can increase blood levels of oral cyclosporine, potentially increasing the effects and adverse effects of cyclosporine.
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Theoretically, grapefruit juice might increase levels of drugs metabolized by CYP1A2.
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In vitro research suggests that grapefruit juice might inhibit CYP1A2 enzymes (12479). So far, this interaction has not been reported in humans.
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Theoretically, grapefruit juice might increase levels of drugs metabolized by CYP2C19.
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In vitro research suggests that grapefruit juice might inhibit CYP2C19 enzymes (12479). Also, a small clinical study shows that taking grapefruit juice with clopidogrel, an antiplatelet prodrug that is metabolized primarily by CYP2C19, decreases plasma levels of the active metabolite and impairs the antiplatelet effect of clopidogrel. This effect is likely due to grapefruit-induced inhibition of CYP2C19 (91419).
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Theoretically, grapefruit juice might increase levels of drugs metabolized by CYP2C9.
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In vitro research suggests that grapefruit juice might inhibit CYP2C9 enzymes (12479). So far, this interaction has not been reported in humans.
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Grapefruit juice can increase levels of drugs metabolized by CYP3A4.
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Clinical research shows that grapefruit juice can inhibit CYP3A4 metabolism of drugs, causing increased drug levels and potentially increasing the risk of adverse effects (3227,3774,8283,8285,8286,22129,91427,104190). When taken orally, effects of grapefruit juice on CYP3A4 levels appear to last at least 48 hours (91427). Grapefruit's ability to inhibit CYP3A4 has even been harnessed to intentionally increase levels of venetoclax, which is metabolized by CYP3A4, in an elderly patient with acute myeloid leukemia who could not afford full dose venetoclax. The lower dose of venetoclax in combination with grapefruit juice resulted in serum levels of venetoclax in the therapeutic reference range of full dose venetoclax and positive treatment outcomes for the patient (112287).
Professional consensus recommends the consideration of patient age, existing medical conditions, additional medications, and the potential for additive adverse effects when evaluating the risks of concomitant use of grapefruit juice with any medication metabolized by CYP3A4. While all patients are at risk for interactions with grapefruit juice consumption, patients older than 70 years of age and those taking multiple medications are at the greatest risk for a serious or fatal interaction with grapefruit juice (95970,95972). |
Grapefruit juice can increase blood levels of dapoxetine, potentially increasing the effects and adverse effects of dapoxetine.
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Pharmacokinetic research shows that drinking grapefruit juice 250 mL prior to taking dapoxetine 60 mg can increase the maximum plasma concentration of dapoxetine by 80% and prolong the elimination half-life by 43%. This effect is attributed to the inhibition of both intestinal and hepatic cytochrome P450 3A4 (CYP3A4) by grapefruit (95975).
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Grapefruit juice can increase blood levels of dextromethorphan, potentially increasing the effects and adverse effects of dextromethorphan.
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Clinical research shows that grapefruit juice can inhibit cytochrome P450 3A4 (CYP3A4) metabolism, causing increased dextromethorphan levels (11362).
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Grapefruit juice can increase blood levels of erythromycin, potentially increasing the effects and adverse effects of erythromycin.
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Clinical research shows that concomitant use of erythromycin with grapefruit can inhibit cytochrome P450 3A4 (CYP3A4) metabolism of erythromycin, increasing plasma concentrations of erythromycin by 35% (8286).
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Grapefruit juice can increase blood levels of estrogens, potentially increasing the effects and adverse effects of estrogens.
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Clinical research shows that grapefruit increases the levels of endogenous and exogenous estrogens by inhibiting cytochrome P450 3A4 (CYP3A4) enzymes (525,526,14858). Grapefruit juice increases exogenously administered 17-beta-estradiol by about 20% in females without ovaries and ethinyl-estradiol in healthy females (525,526,22160).
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Grapefruit juice can decrease blood levels of etoposide, potentially decreasing the clinical effects of etoposide.
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Clinical research shows that grapefruit juice decreases the absorption and plasma concentrations of etoposide. There is some evidence that grapefruit juice co-administered with oral etoposide can reduce levels of etoposide by about 26% (8744). Grapefruit juice seems to inhibit organic anion transporting polypeptide (OATP), which is a drug transporter in the gut, liver, and kidney (7046,17603,17604). Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction (17603,17604).
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Grapefruit juice can decrease blood levels of fexofenadine, thereby decreasing the clinical effects of fexofenadine.
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Clinical research shows that grapefruit juice can significantly decrease oral absorption and blood levels of fexofenadine. In one study, consuming a drink containing grapefruit juice 25% decreased bioavailability of fexofenadine by about 24%. Consuming a full-strength grapefruit juice drink reduced bioavailability by 67% (7046). In another study, consuming grapefruit juice 300 mL decreased fexofenadine levels by 42%. Consuming 1200 mL of grapefruit juice reduced levels by 64% (17602). Similarly, drinking grapefruit juice 240 mL decreased the oral bioavailability of fexofenadine by 25% in another pharmacokinetic study (112288). Fexofenadine manufacturer data indicates that concomitant administration of grapefruit juice and fexofenadine results in larger wheal and flare sizes in research models. This suggests that grapefruit also reduces the clinical response to fexofenadine (17603).
Grapefruit juice seems to inhibit organic anion transporting polypeptide (OATP), which is a drug transporter in the gut, liver, and kidney (7046,17603,17604,22161). Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction (17603,17604). |
Grapefruit juice can increase blood levels of fluvoxamine, potentially increasing the effects and adverse effects of fluvoxamine.
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Clinical research shows that grapefruit juice inhibits metabolism and increases fluvoxamine levels and peak concentration (17675).
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Grapefruit juice can increase blood levels of halofantrine, potentially increasing the effects and adverse effects of halofantrine.
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Clinical research shows that grapefruit juice inhibits cytochrome P450 3A4 (CYP3A4) metabolism, which increases halofantrine levels and peak concentration, as well as a marker of ventricular tachyarrhythmia potential (22129).
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Grapefruit juice can increase blood levels of statins that are metabolized by cytochrome P450 3A4 (CYP3A4), potentially increasing the effects and adverse effects of these statins. Additionally, grapefruit juice might interfere with the bioavailability of statins that are substrates of organic anion transporting polypeptides (OATP).
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Clinical research shows that grapefruit juice inhibits metabolism and increases absorption and plasma concentrations of statins that are metabolized by CYP3A4. These include lovastatin (527,11274), simvastatin (3774,7782,22127), and atorvastatin (3227,12179,22126). Keep in mind that there is considerable variability in the effect of grapefruit juice on drug metabolism, so individual patient response is difficult to predict (7777,7781).
Some statins, including pravastatin, fluvastatin, pitavastatin, and rosuvastatin, are not metabolized by CYP3A4. However, grapefruit juice might still affect the bioavailability of these statins. These statins are substrates of OATP. Grapefruit juice can inhibit OATP. Therefore, grapefruit juice may reduce the bioavailability or increase drug levels of these statins depending on the type of OATP. However, grapefruit juice affects OATP for only a short time. Therefore, separating drug administration by at least 4 hours is likely to avoid this interaction (3227,12179,17601,22126,91420). |
Grapefruit juice can interfere with itraconazole absorption, although the clinical significance of this interaction is unclear.
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Grapefruit juice can decrease blood levels of levothyroxine, potentially decreasing the effectiveness of levothyroxine.
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Clinical research shows that grapefruit juice modestly decreases levothyroxine levels by 11% by inhibiting organic anion transporting polypeptide (OATP) (17604,22163). Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction (17603,17604).
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Grapefruit juice can decrease blood levels of the active metabolite of losartan, potentially decreasing the clinical effects of losartan.
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Losartan is an inactive prodrug which must be metabolized to its active form, E-3174, to be effective. In one human study, grapefruit juice reduced losartan metabolism, increased losartan AUC, and reduced the AUC of the major active losartan metabolite, E-3174 (1391).
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Grapefruit juice can increase blood levels of methadone, potentially increasing the effects and adverse effects of methadone.
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Clinical research shows that grapefruit juice inhibits the metabolism of methadone, increasing methadone levels and peak concentrations (17676). In one case, a 51-year-old male taking methadone 90 mg daily and no other medications was found unresponsive. The patient reported drinking grapefruit juice 500 mL daily for 3 days prior to the event. Methadone is a substrate of cytochrome P450 3A4 (CYP3A4), and grapefruit juice-induced inhibition of CYP3A4 is the likely cause of this interaction (102056).
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Grapefruit juice can increase blood levels of methylprednisolone, potentially increasing the effects and adverse effects of methylprednisolone.
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Clinical research shows that grapefruit juice can increase the plasma concentration of orally administered methylprednisolone. Grapefruit juice 200 mL three times daily given with methylprednisolone 16 mg increased methylprednisolone half-life by 35%, peak plasma concentration by 27%, and total area under the curve by 75% (3123).
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Grapefruit juice might decrease blood levels of nadolol, potentially decreasing the clinical effects of nadolol.
Details
Nadolol is a substrate of organic anion transporting polypeptide 1A2 (OATP1A2) (17603,17604,22161). Some research shows that grapefruit juice and its constituent naringin can inhibit organic anion transporting polypeptides (OATP), which can reduce the bioavailability of OATP substrates (17603,17604,22161,91427). However, preliminary clinical research shows that grapefruit juice containing a low amount of naringin does not significantly affect levels of nadolol (91422). It is not known if grapefruit juice containing higher amounts of naringin reduces the bioavailability of nadolol.
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Grapefruit juice can increase blood levels of nilotinib, potentially increasing the effects and adverse effects of nilotinib.
Details
Clinical research shows that grapefruit juice inhibits metabolism and increases absorption of nilotinib. Grapefruit juice increases nilotinib levels by 29% and peak concentration by 60% (17677).
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Grapefruit juice can decrease levels of drugs that are substrates of OATP.
Details
In vitro and clinical research show that consuming grapefruit juice inhibits OATP, which reduces the bioavailability of oral drugs that are substrates of OATP. Various clinical studies have shown reduced absorption of OATP substrates when taken with grapefruit, including fexofenadine, acebutolol, aliskiren, celiprolol, levothyroxine, nadolol, and pitavastatin (17603,17604,18101,22126,22134,22161,22163,91420,91427,91428,112288). Grapefruit juice is thought to affect OATP for only a short time. Therefore, separating drug administration and consumption of grapefruit by at least 4 hours is likely to prevent this interaction (17603,17604).
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Grapefruit juice can increase blood levels of oxycodone, potentially increasing the effects and adverse effects of oxycodone.
Details
Oxycodone is metabolized by both cytochrome P450 3A4 (CYP3A4) and cytochrome P450 2D6 (CYP2D6). A small clinical study shows that grapefruit juice can increase plasma levels of oral oxycodone about 1.7-fold by inhibiting CYP3A4. While the analgesic effects of oxycodone do not seem to be affected, taking grapefruit juice along with oxycodone may theoretically increase the adverse effects of oxycodone (91423).
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Grapefruit juice does not seem to affect renal P-glycoprotein (P-gp). Theoretically, it might inhibit intestinal P-gp, but evidence is conflicting.
Details
While most in vitro research shows that grapefruit products inhibit P-gp, (1390,11270,11278,11362,95976), research in humans is less clear. Two small clinical studies in healthy adults using digoxin as a probe substrate show that grapefruit juice does not inhibit P-gp in the kidneys (11277,11282). It is unclear whether this applies to intestinal P-gp, for which digoxin is not considered to be a sensitive probe (105568). Grapefruit juice has been shown to reduce levels of fexofenadine (7046,17602,112288), and increase levels of quinidine (5067,22121). However, as both of these drugs are also substrates of other enzymes and transporters, it is unclear what role, if any, intestinal P-gp has in these findings.
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Grapefruit juice can increase blood levels of pitavastatin, potentially increasing the effects and adverse effects of pitavastatin.
Details
Pharmacokinetic research shows that taking grapefruit juice with pitavastatin 2-4 mg can increase blood levels of pitavastatin by 13% to 14%. Unlike simvastatin and atorvastatin, pitavastatin is not significantly metabolized by cytochrome P450 3A4 (CYP3A4) enzymes. Grapefruit juice appears to increase levels of pitavastatin by inhibiting its uptake by organic anion transporting polypeptide 1B1 (OATP1B1) into hepatocytes for metabolism and clearance from the body (22126,91420). Grapefruit juice seems to increase levels of pitavastatin to a greater degree in patients homozygous for a specific polymorphism (388A>G) in the OATP1B1 gene compared to those heterozygous for this polymorphism (91420).
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Grapefruit juice can decrease blood levels of the active metabolite of prasugrel, thereby decreasing the antiplatelet effect of prasugrel.
Details
Prasugrel is a prodrug that is metabolized by cytochrome P450 3A4 (CYP3A4) into its active metabolite. A small pharmacokinetic study in healthy volunteers shows that drinking grapefruit juice 200 mL three times daily for 4 days and taking a single dose of prasugrel 10 mg with an additional 200 mL of grapefruit juice on day 3, results in a 49% lower peak plasma level and a 26% lower overall plasma exposure to the active metabolite when compared with drinking water. However, despite the reduced exposure, platelet aggregation seems to be reduced by an average of only 5% (105567). The clinical significance of this interaction is unclear.
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Grapefruit juice can increase blood levels of praziquantel, potentially increasing the effects and adverse effects of praziquantel.
Details
Clinical research shows that grapefruit juice can inhibit cytochrome P450 3A4 (CYP3A4) metabolism of praziquantel. Plasma concentrations of praziquantel can increase by as much as 160% when administered with 250 mL of commercially available grapefruit juice (8282).
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Grapefruit juice may increase blood levels of primaquine, potentially increasing the effects and adverse effects of primaquine.
Details
Clinical research shows that grapefruit juice increases the bioavailability of primaquine by approximately 20% (22130). The clinical significance of this interaction is not clear.
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Grapefruit or grapefruit juice, especially if consumed in large amounts, can cause additive QT interval prolongation when taken with QT interval-prolonging drugs, potentially increasing the risk of ventricular arrhythmias.
Details
Clinical research in healthy volunteers shows that drinking 6 liters of grapefruit juice over 6 hours prolonged the QTc by a peak amount of 14 milliseconds (ms). This prolongation was similar to the QT prolongation caused by the drug moxifloxacin. In individuals with long QT syndrome, a smaller dose of grapefruit juice, 1.5 liters, resulted in a greater peak QTc prolongation of about 30 ms (100249). The effect of smaller quantities of grapefruit juice on the QT interval is unclear.
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Grapefruit juice may increase blood levels of quetiapine, increasing the effects and adverse effects of quetiapine.
Details
Quetiapine is metabolized by cytochrome P450 3A4 (CYP3A4). Grapefruit can inhibit CYP3A4 (3227,3774,8283,8285,8286,22129,91427,104190). In one case report, a healthy 28-year-old female with bipolar disorder stabilized on quetiapine 800 mg daily presented with quetiapine toxicity considered to be related to consuming a gallon of grapefruit juice over the past 24 hours (108848).
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Grapefruit juice can alter blood levels of quinidine, potentially increasing or decreasing the clinical effects of quinidine.
Details
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Grapefruit juice can increase blood levels of saquinavir, potentially increasing the effects and adverse effects of saquinavir.
Details
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Grapefruit juice can increase blood levels of scopolamine, potentially increasing the effects and adverse effects of scopolamine.
Details
Clinical research shows that grapefruit juice can inhibit cytochrome P450 3A4 (CYP3A4) metabolism of scopolamine, increasing its absorption and plasma concentrations. Oral bioavailability of scopolamine can increase by 30% when administered with 150 mL of grapefruit juice (8284).
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Grapefruit juice can increase blood levels of sertraline, potentially increasing the effects and adverse effects of sertraline.
Details
Clinical research shows that grapefruit juice inhibits the cytochrome P450 3A4 (CYP3A4) metabolism of sertraline, increasing blood levels of sertraline (22122).
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Grapefruit juice can increase blood levels of sildenafil, potentially increasing the effects and adverse effects of sildenafil.
Details
Clinical research shows that grapefruit juice inhibits cytochrome P450 3A4 (CYP3A4) metabolism of sildenafil, increasing its absorption and plasma concentrations. Oral bioavailability of sildenafil can increase by 23% when administered with 500 mL of commercially available grapefruit juice (8283).
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Grapefruit juice may slightly increase blood levels of sunitinib, potentially increasing the effects and adverse effects of sunitinib.
Details
Sunitinib is metabolized by cytochrome P450 3A4 (CYP3A4). Grapefruit and grapefruit juice can inhibit CYP3A4 and increase levels of some drugs metabolized by this enzyme. One small clinical study shows that drinking 200 mL of grapefruit juice three times daily can increase the bioavailability of sunitinib by 11% (91429). While this effect is unlikely to be clinically significant, patients should use caution when using grapefruit along with sunitinib. Dose adjustments may be necessary.
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Grapefruit juice can increase blood levels of tacrolimus, potentially increasing the effects and adverse effects of tacrolimus.
Details
Clinical research shows that drinking grapefruit juice 200 mL daily while taking tacrolimus 3 mg daily increases the trough blood concentration of tacrolimus by approximately 3-fold in patients with connective tissue diseases (95974). A single case has also reported a 10-fold increase in tacrolimus trough levels after the ingestion of grapefruit juice over 3 days (22122). This effect is attributed to the inhibition of cytochrome P450 3A4 (CYP3A4) by grapefruit (95974).
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Theoretically, grapefruit juice might increase blood levels of tadalafil, potentially increasing the effects and adverse effects of tadalafil.
Details
Animal research shows that grapefruit juice increases tadalafil serum concentrations and overall exposure, likely through inhibition of cytochrome P450 3A4 enzymes (104189).
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Grapefruit juice might decrease blood levels of talinolol, potentially decreasing the clinical effects of talinolol.
Details
Clinical research suggests that grapefruit juice reduces talinolol bioavailability, likely by inhibiting intestinal uptake (22135). The clinical significance of this effect is unclear.
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Grapefruit juice can increase blood levels of terfenadine, potentially increasing the effects and adverse effects of terfenadine.
Details
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Grapefruit juice can decrease blood levels of theophylline, potentially decreasing the effectiveness of theophylline.
Details
Clinical research shows that grapefruit juice seems to modestly decrease theophylline levels when given concurrently with sustained-release theophylline (11013). The mechanism of this interaction is unknown.
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Grapefruit juice can increase blood levels of ticagrelor, thereby increasing the effects and adverse effects of ticagrelor.
Details
Ticagrelor is metabolized by cytochrome P450 3A4 (CYP3A4). Grapefruit can inhibit CYP3A4. A small clinical study shows that taking grapefruit juice with ticagrelor increases blood levels of ticagrelor more than two-fold and increases the antiplatelet activity of ticagrelor (91418).
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Grapefruit juice can increase blood levels of tolvaptan, potentially increasing the effects and adverse effects of tolvaptan.
Details
Tolvaptan is metabolized by cytochrome P450 3A4 (CYP3A4). Grapefruit can inhibit CYP3A4. A small clinical study shows that grapefruit juice can increase the bioavailability and blood levels of tolvaptan by approximately 1.6-fold for up to 16 hours (91426).
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Theoretically, drinking large amounts of grapefruit juice might increase the effects and adverse effects of warfarin.
Details
In one case report, a patient experienced significantly increased international normalized ratio (INR) associated with consumption of 50 ounces of grapefruit juice daily (12061). However, smaller amounts of grapefruit juice might not be a problem. In a small clinical trial, consumption of 24 ounces of grapefruit juice daily for one week had no effect on INR in males treated with warfarin (12063).
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Theoretically, hesperidin may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Details
Animal research suggests that hesperetin, a bioflavonoid aglycone derivative of hesperidin, may have antiplatelet activity (54822).
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Theoretically, taking hesperidin with antihypertensive drugs might increase the risk of hypotension.
Details
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Theoretically, hesperidin may decrease the levels and clinical effects of celiprolol.
Details
Animal research shows that concomitant use of hesperidin may reduce the plasma area under the curve of celiprolol by up to 75% (91760). This effect has not been reported in humans.
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Theoretically, concomitant use with CNS depressants may cause additive sedative effects.
Details
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Theoretically, hesperidin may increase the levels and clinical effects of diltiazem.
Details
Animal research suggests that hesperidin may enhance the bioavailability of diltiazem, increasing the plasma area under the curve of diltiazem by up to 65.3% (91761). This effect has not been reported in humans.
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Theoretically, hesperidin might inhibit P-glycoprotein-mediated drug efflux and potentially increase levels of drugs that are substrates of P-glycoprotein.
Details
In vitro research shows that hesperidin can inhibit P-glycoprotein efflux (54908). This effect has not been reported in humans.
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Theoretically, hesperidin might increase the levels and clinical effects of verapamil.
Details
Animal research suggests that hesperidin may enhance the bioavailability of verapamil, increasing the plasma area under the curve of verapamil by 96.8% (91762). This effect has not been reported in humans
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Theoretically, taking itraconazole capsules or tablets with a beverage containing lemon might increase the levels and clinical effects of itraconazole.
Details
In one case report, dissolving itraconazole tablets in a small amount of specific beverages containing lemon prior to administration increased the level of itraconazole in a lung transplant patient. In this case, the increased bioavailability was desirable and was likely due to improved tablet dissolution in the acidic beverage (110781).
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Theoretically, taking rutin with antidiabetes drugs might increase the risk of hypoglycemia.
Details
Animal research suggests that rutin has hypoglycemic effects (105299).
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Consuming sweet orange with celiprolol can decrease oral absorption of celiprolol.
Details
A pharmacokinetic study in healthy volunteers shows that celiprolol levels, after a single dose of 100 mg, are decreased by up to 90% in people who drink sweet orange juice 200 mL three times daily. It's not known if lower consumption of sweet orange juice will have the same effect. Theoretically, this occurs due to short-term inhibition of organic anion transporting polypeptide (OATP) (12115,17603,17604). Recommend separating drug administration and consumption of sweet orange by at least 4 hours (17603,17604).
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Consuming sweet orange juice with fexofenadine can decrease oral absorption of fexofenadine.
Details
Clinical research shows that coadministration of sweet orange juice 1200 mL decreases bioavailability of fexofenadine by about 72% (7046,17604). In an animal model, sweet orange juice decreased bioavailability of fexofenadine by 31% (17605). Fexofenadine manufacturer data indicates that concomitant administration of sweet orange juice and fexofenadine results in larger wheal and flare sizes in research models. This suggests that sweet orange reduces the clinical response to fexofenadine (17603). Theoretically, this occurs due to short-term inhibition of organic anion transporting polypeptide (OATP) (7046). Recommend separating drug administration and consumption of sweet orange by at least 4 hours (17603,17604).
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Consuming sweet orange juice with ivermectin can decrease the oral absorption of ivermectin.
Details
A pharmacokinetic study in healthy volunteers shows that taking ivermectin orally with sweet orange juice 750 mL over 4 hours reduces the bioavailability of ivermectin. This effect does not seem to be related to effects on P-glycoprotein. The effect on ivermectin is more pronounced in males compared to females (12154).
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Consuming sweet orange juice can decrease oral absorption of OATP substrates. Separate administration by at least 4 hours.
Details
Clinical research shows that consuming sweet orange juice inhibits OATP, which reduces bioavailability of oral drugs that are substrates of OATP (17603,17604). For example, sweet orange juice decreases bioavailability of fexofenadine, a substrate of OATP, by about 72% and of celiprolol, another OATP substrate, by up to 90% (7046,12115). Since sweet orange juice seems to affect OATP for a short time, recommend separating drug administration and consumption of sweet orange juice by at least 4 hours (17603,17604).
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Sweet orange juice seems to modulate P-glycoprotein (P-gp), which might affect the blood levels of P-gp substrates.
Details
Animal and in vitro research suggest that orange juice extract inhibits drug efflux by P-gp, increasing absorption and levels of P-gp substrates (12116,15327). In contrast, pharmacokinetic research in humans shows that drinking large amounts of sweet orange juice decreases absorption and levels of the P-gp substrate celiprolol. This suggests that orange juice actually induces drug efflux by P-gp or affects drug levels by another mechanism such as inhibiting the gut drug transporter called organic anion transporting polypeptide (OATP) (7046,12115). Until more is known, sweet orange juice should be used cautiously in people taking P-gp substrates.
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Consuming sweet orange juice with pravastatin can increase the absorption of pravastatin.
Details
A small pharmacokinetic study in healthy volunteers shows that consuming sweet orange juice 800 mL over 3 hours, including before, during, and after taking pravastatin 10 mg, increases pravastatin levels by about 149%, without affecting pravastatin elimination. Theoretically this effect might be due to modulation of organic anion transporting polypeptides (OATPs) by sweet orange juice (14348). Sweet orange juice does not seem to affect simvastatin levels, but it is not known if sweet orange affects any of the other statins.
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Calcium-fortified sweet orange juice might reduce quinolone absorption.
Details
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High-dose vitamin C might slightly prolong the clearance of acetaminophen.
Details
A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases (6451). This effect is not likely to be clinically significant.
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Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.
Details
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.
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Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.
Details
Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption (10549,10550,10551,21556). In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely (10549). Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.
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Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.
Details
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin (391). In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells (14012,14013). More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.
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Acidification of the urine by vitamin C might increase aspirin levels.
Details
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction is not clinically significant.
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Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.
Details
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046,4531). However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.
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Vitamin C might increase blood levels of estrogens.
Details
Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products (129,130,11161). It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall (129,11161). When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements (11161). Monitor these patients for estrogen-related side effects.
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Theoretically, vitamin C might decrease levels of fluphenazine.
Details
In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started (11017). The mechanism is not known, and there is no further data to confirm this interaction.
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Vitamin C can modestly reduce indinavir levels.
Details
One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown (11300,93578).
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Vitamin C can increase levothyroxine absorption.
Details
Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH (102978).
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Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.
Details
A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease (7388,11537). It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.
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Acidification of the urine by vitamin C might increase salsalate levels.
Details
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels (3046). However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion (10588,10589), suggesting this interaction probably is not clinically significant.
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High-dose vitamin C might reduce the levels and effectiveness of warfarin.
Details
Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption (11566). There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time (9804,9806). Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant (9805,9806,11566,11567). However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR) (90942). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.
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Below is general information about the adverse effects of the known ingredients contained in the product Hypoallergenic Maxi C Caps. Some ingredients may not be listed. This information does NOT represent a recommendation for or a test of this specific product as a whole.
General
...Orally, diosmin is generally well tolerated.
Most Common Adverse Effects:
Orally: Abdominal pain, diarrhea, dizziness, gastritis, nausea, skin inflammation, and skin redness.
Serious Adverse Effects (Rare):
Orally: Cardiac arrhythmias and hemolytic anemia.
Cardiovascular ...Orally, diosmin can cause cardiac arrhythmias (93887,105293).
Dermatologic ...Orally, diosmin can cause skin redness, hives, itchiness, and inflammation (93887).
Gastrointestinal ...Orally, diosmin can cause gastrointestinal side effects, including abdominal pain, diarrhea, nausea, flatulence, and gastritis (4861,4898,4900,10229,54935,54970,93887,105287,105293,105296)(112796). In one case, exacerbation of chronic colopathy was reported after taking a specific diosmin-containing product (Daflon 500, Les Laboratoires Servier) (10229).
Hematologic ...Orally, diosmin can cause hemolytic anemia (93887).
Musculoskeletal ...Orally, one case report of muscle pain was thought to be related to diosmin use (93887).
Neurologic/CNS ...Orally, diosmin can cause headache, low energy, and dizziness in some patients (4861,4898,4900,10229,93887,105293,112796).
General
...Orally, grapefruit and grapefruit juice are generally well tolerated.
Serious Adverse Effects (Rare):
Orally: Allergic reactions in sensitive individuals have been reported. When large quantities are consumed, arrhythmias, mineralocorticoid excess, QT prolongation, and pseudohyperaldosteronism have been reported. There is also some concern for increased breast cancer risk with grapefruit consumption.
Cardiovascular ...Orally, consumption of pink grapefruit juice 1000 mL can cause QT prolongation and cause arrhythmias in healthy patients and worsen arrhythmias in cardiomyopathy patients (13031,91424).
Endocrine ...Orally, high doses of grapefruit juice have been observed to cause pseudohyperaldosteronism and mineralocorticoid excess (53340,53346).
Gastrointestinal ...In a case report, grapefruit juice held against the teeth resulted in enamel and tooth surface loss (53368).
Immunologic ...Orally, grapefruit can cause allergic sensitization characterized by eosinophilic gastroenteritis, urticaria, and generalized pruritus (53351,53360).
Oncologic ...Preliminary population research shows that postmenopausal adults who consume a quarter or more of a whole grapefruit daily have a 25% to 30% increased risk of developing breast cancer (14858). Grapefruit is a potent inhibitor of cytochrome P450 3A4, which metabolizes estrogen. Consuming large amounts of grapefruit might significantly increase endogenous estrogen levels and therefore increase the risk of breast cancer. More evidence is needed to validate these findings. Until more is known, advise patients to consume grapefruit in moderation.
Renal ...In population research, consumption of 240 mL/day of grapefruit juice is associated with an increased risk of kidney stones (4216,53372).
General ...Orally, hesperidin is generally well tolerated.
Dermatologic ...A case of recurrent allergic dermatitis was reported in a 70-year-old female with no known allergies who applied topical hesperidin methyl chalchone (94538).
Immunologic ...A case of recurrent allergic dermatitis was reported in a 70-year-old female with no known allergies who applied topical hesperidin methyl chalchone (94538).
General
...Orally, lemon is well tolerated in amounts commonly found in foods.
A thorough evaluation of safety outcomes has not been conducted on the use of larger amounts.
Most Common Adverse Effects:
Orally: Epigastralgia and heartburn with the regular consumption of fresh lemon juice.
Dermatologic ...Topically, the application of lemon oil might cause photosensitivity, due to furocoumarin derivative content. This occurs most often in fair-skinned people (11019).
Gastrointestinal ...Orally, fresh lemon juice, taken as 60 mL twice daily, has been reported to cause gastrointestinal disturbances in 37% of patients in one clinical trial, compared with 8% of patients in the placebo group. Specifically, of the patients consuming lemon juice, 21% experienced heartburn and 8% experienced epigastralgia, compared to 1% and 3%, respectively, in the placebo group (107489).
General ...Orally, rutin is generally well tolerated.
Dermatologic ...Orally, rutin may cause flushing and rashes in some people (313).
Gastrointestinal ...Orally, rutin may cause gastrointestinal disturbance in some people (313).
Neurologic/CNS ...Orally, rutin may cause headache in some people (313).
General ...Orally, sweet orange juice or fruit seem to be well tolerated. Large amounts of sweet orange peel may be unsafe, especially for children. When inhaled, sweet orange essential oil seems to be generally well tolerated.
Gastrointestinal ...There have been reports of intestinal colic in children following ingestion of large amounts of sweet orange peel (11).
Neurologic/CNS ...There have been reports of convulsions in children following ingestion of large amounts of sweet orange peel (11).
General
...Orally, intravenously, and topically, vitamin C is well-tolerated.
Most Common Adverse Effects:
Orally: Abdominal cramps, esophagitis, heartburn, headache, osmotic diarrhea, nausea, vomiting. Kidney stones have been reported in those prone to kidney stones. Adverse effects are more likely to occur at doses above the tolerable upper intake level of 2 grams daily.
Topically: Irritation and tingling.
Serious Adverse Effects (Rare):
Orally: There have been rare case reports of carotid inner wall thickening after large doses of vitamin C.
Intravenously: There have been case reports of hyperoxalosis and oxalate nephropathy following high-dose infusions of vitamin C.
Cardiovascular
...Evidence from population research has found that high doses of supplemental vitamin C might not be safe for some people.
In postmenopausal adults with diabetes, supplemental vitamin C intake in doses greater than 300 mg per day is associated with increased risk of cardiovascular mortality. However, dietary intake of vitamin C is not associated with this risk. Also, vitamin C intake is not associated with an increased risk of cardiovascular mortality in patients without diabetes (12498).
Oral supplementation with vitamin C has also been associated with an increased rate of carotid inner wall thickening in men. There is preliminary evidence that supplemental intake of vitamin C 500 mg daily for 18 months can cause a 2.5-fold increased rate of carotid inner wall thickening in non-smoking men and a 5-fold increased rate in men who smoked. The men in this study were 40-60 years old (1355). This effect was not associated with vitamin C from dietary sources (1355).
There is also some concern that vitamin C may increase the risk of hypertension in some patients. A meta-analysis of clinical research suggests that, in pregnant patients at risk of pre-eclampsia, oral intake of vitamin C along with vitamin E increases the risk of gestational hypertension (83450). Other clinical research shows that oral intake of vitamin C along with grape seed polyphenols can increase both systolic and diastolic blood pressure in hypertensive patients (13162). Three cases of transient hypotension and tachycardia during intravenous administration of vitamin C have also been reported (114490).
Dental ...Orally, vitamin C, particularly chewable tablets, has been associated with dental erosion (83484).
Dermatologic ...Topically, vitamin C might cause tingling or irritation at the site of application (6166). A liquid containing vitamin C 20%, red raspberry leaf cell culture extract 0.0005%, and vitamin E 1% (Antioxidant and Collagen Booster Serum, Max Biocare Pty Ltd.) has been reported to cause mild tingling and skin tightness (102355). It is unclear if these effects are due to vitamin C, the other ingredients, or the combination.
Gastrointestinal ...Orally, the adverse effects of vitamin C are dose-related and include nausea, vomiting, esophagitis, heartburn, abdominal cramps, gastrointestinal obstruction, and diarrhea. Doses greater than the tolerable upper intake level (UL) of 2000 mg per day can increase the risk of adverse effects such as osmotic diarrhea and severe gastrointestinal upset (3042,4844,96707,104450,114493,114490). Mineral forms of vitamin C, such as calcium ascorbate (Ester-C), seem to cause fewer gastrointestinal adverse effects than regular vitamin C (83358). In a case report, high dose intravenous vitamin C was associated with increased thirst (96709).
Genitourinary ...Orally, vitamin C may cause precipitation of urate, oxalate, or cysteine stones or drugs in the urinary tract (10356). Hyperoxaluria, hyperuricosuria, hematuria, and crystalluria have occurred in people taking 1 gram or more per day (3042,90943). Supplemental vitamin C over 250 mg daily has been associated with higher risk for kidney stones in males. There was no clear association found in females, but the analysis might not have been adequately powered to evaluate this outcome (104029). In people with a history of oxalate kidney stones, supplemental vitamin C 1 gram per day appears to increase kidney stone risk by 40% (12653). A case of hematuria, high urine oxalate excretion, and the presence of a ureteral stone has been reported for a 9-year-old male who had taken about 3 grams of vitamin C daily since 3 years of age. The condition resolved with cessation of vitamin C intake (90936).
Hematologic ...Prolonged use of large amounts of vitamin C can result in increased metabolism of vitamin C; subsequent reduction in vitamin C intake may precipitate the development of scurvy (15). In one case, a patient with septic shock and a large intraperitoneal hematoma developed moderate hemolysis and increased methemoglobin 12 hours after a high-dose vitamin C infusion. The patient received a blood transfusion and the hemolysis resolved spontaneously over 48 hours (112479).
Neurologic/CNS ...Orally, the adverse effects of vitamin C are dose-related and include fatigue, headache, insomnia, and sleepiness (3042,4844,83475,83476).
Renal ...Hyperoxalosis and oxalate nephropathy have been reported following high-dose infusions of vitamin C. Hyperoxalosis and acute kidney failure contributed to the death of a 76-year-old patient with metastatic adenocarcinoma of the lung who received 10 courses of intravenous infusions containing vitamins, including vitamin C and other supplements over a period of 1 month. Dosages of vitamin C were not specified but were presumed to be high-dose (106618). In another case, a 34-year-old patient with a history of kidney transplant and cerebral palsy was found unresponsive during outpatient treatment for a respiratory tract infection. The patient was intubated for acute hypoxemic respiratory failure, initiated on vasopressors, hydrocortisone, and antibacterial therapy, and received 16 doses of vitamin C 1.5 grams. Serum creatinine level peaked at greater than 3 times baseline and the patient required hemodialysis for oliguria and uncontrolled acidosis. Kidney biopsy revealed oxalate nephropathy with concomitant drug-induced interstitial nephritis (106625). In another case, a 41-year-old patient with a history of kidney transplant presented with fever, nausea, and decreased urine output 4 days after receiving intravenous vitamin C 7 grams for urothelial carcinoma. Serum creatinine levels increased from 1.7 mg/dL to 7.3 mg/dL over those 4 days, and hemodialysis was initiated 3 days after admission due to anuria. Renal biopsy confirmed the diagnosis of acute oxalate nephropathy (109962).
Other ...Intravenously, hypernatremia and falsely elevated ketone levels is reported in a patient with septic shock and chronic kidney disease after a high-dose vitamin C infusion. The hypernatremia resolved over 24 hours after cessation of the infusion (112479).
