Two capsules contain: Feverfew leaf (tanacetum parthenium) (min. 0.9% Parthenolide) 400 mg • Kava root extract (piper methysticum) (30% kavalactones) 100 mg • Ginger root extract (zingiber officinale) 5% standardized 50 mg • Proprietary Blend 50 mg: Purple Willow Bark (salix purpurea), Meadow Sweet (filipendula ulmaria), Wintergreen (gaultheria procumbens).
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 Head Relief. 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
Below is general information about the safety of the known ingredients contained in the product Head Relief. 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 and appropriately, short-term. Feverfew has been used safely in studies lasting up to 4 months (6959,6960,6961,13239).
POSSIBLY UNSAFE ...when fresh feverfew leaves are chewed. Chewing raw or unprocessed feverfew leaves can cause oral inflammation, ulceration, swelling of the lips, and sometimes loss of taste (6959).
PREGNANCY: POSSIBLY UNSAFE
when used orally.
Feverfew might cause uterine contractions and abortion (12); avoid using.
LACTATION:
Insufficient reliable information available; avoid using.
LIKELY SAFE ...when used orally and appropriately. Ginger has been safely used in multiple clinical trials (721,722,723,5343,7048,7084,7085,7400,7623,11346)(12472,13080,13237,13244,17369,17928,17929,89889,89890,89894)(89895,89898,89899,90102,96252,96253,96259,96260,96669) (101760,101761,101762,103359,107903).
POSSIBLY SAFE ...when used topically and appropriately, short-term (89893,89897).
CHILDREN: LIKELY SAFE
when consumed in the amounts typically found in foods.
CHILDREN: POSSIBLY SAFE
when used orally and appropriately, short-term.
Ginger powder has been used with apparent safety at a dose of up to 750 mg daily for 4 days in girls aged 14-18 years (96255).
PREGNANCY: LIKELY SAFE
when consumed in the amounts typically found in foods.
PREGNANCY: POSSIBLY SAFE
when used for medicinal purposes.
Despite some early reports of adverse effects (721,7083) and one observational study suggesting that taking dried ginger and other herbal supplements during the first 20 weeks of pregnancy marginally increased the chance of stillbirth (96254), most research shows that ginger is unlikely to cause harm to the baby. The risk for major malformations in infants of parents who took ginger when pregnant does not appear to be higher than the baseline rate of 1% to 3% (721,1922,5343,11346,13071,13080,96254). Also, other research suggests that ginger intake during various trimesters does not significantly affect the risk of spontaneous abortion, congenital malformations, stillbirth, perinatal death, preterm birth, low birth weight, or low Apgar scores (18211,90103). Ginger use has been associated with an increase in non-severe vaginal bleeding, including spotting, after week 17 of pregnancy (18211).
LACTATION: LIKELY SAFE
when consumed in the amounts typically found in foods.
There is insufficient reliable information available about the safety of ginger when used for medicinal purposes; avoid amounts greater than those found in foods.
POSSIBLY SAFE ...when used orally, short-term. Kava extracts have been used safely in clinical trials under medical supervision for up to 6 months (2093,2094,2095,4032,7325,15046,15130,18314,18316,18318)(18320,29663,29671,98980,102086,112642). Historically, there has been some concern that kava preparations could induce hepatotoxicity and liver failure in patients taking relatively normal doses, short-term. At least 100 cases of liver toxicity following kava use have been reported. Although liver toxicity is more frequently associated with prolonged use of very high doses (6401,57346), in some cases the use of kava for as little as 1-3 months has been associated with the need for liver transplants, and even death (390,7024,7068,7086,7096,17086,57252)(57254,57297). However, some experts question the clinical validity of several of these cases (11369,11371).
PREGNANCY: POSSIBLY UNSAFE
when used orally.
There is some concern that pyrone constituents in kava can cause loss of uterine tone (19); avoid using.
LACTATION: POSSIBLY UNSAFE
when used orally.
There is concern that the toxic pyrone constituents of kava can pass into breast milk (19); avoid using.
POSSIBLY SAFE ...when used orally and appropriately, short-term (12). Meadowsweet flower has been used with apparent safety at doses of 2.5-3.5 grams daily. Meadowsweet herb has been used with apparent safety at doses of 4-5 grams daily (12).
POSSIBLY UNSAFE ...when used in large amounts or for prolonged periods of time. Meadowsweet contains salicylates and high amounts of tannins (4).
PREGNANCY: LIKELY UNSAFE
when used orally.
Some evidence suggests meadowsweet might stimulate uterine activity (4).
LACTATION:
Insufficient reliable information available; avoid using.
POSSIBLY SAFE ...when used orally and appropriately, short-term. Willow bark has been used safely for up to 12 weeks (6456,12474,12475,12804,12811,86473,91406).
CHILDREN: POSSIBLY UNSAFE
when used orally for viral infections.
Salicylic acid and aspirin are contraindicated in children with viral infections (12801). Although Reye's syndrome has not been reported, the salicin constituent in willow bark is similar to aspirin and might pose the same risk.
PREGNANCY:
Insufficient reliable information available; avoid using.
LACTATION: POSSIBLY UNSAFE
when used orally.
Willow bark contains salicylates which are excreted in breast milk and have been linked to adverse effects in breast-fed infants (12802,12803).
LIKELY SAFE ...when used orally in very small amounts commonly found in foods. Wintergreen oil has Generally Recognized As Safe status (GRAS) in the US (4912) The highest concentration recommended for use as a food flavoring is 0.04% (6).
POSSIBLY SAFE ...when wintergreen leaf is used orally and appropriately in medicinal amounts (12). ...when wintergreen oil is used topically and appropriately (272).
POSSIBLY UNSAFE ...when wintergreen oil is used orally. Wintergreen oil contains large amounts of methyl salicylate, which is toxic (272). Ingesting as little as 6 mL can be lethal for an adult (6). One teaspoon (5 mL) of wintergreen oil is equivalent to approximately 7 grams of salicylate, or more than 20 adult aspirin tablets (6).
CHILDREN: LIKELY UNSAFE
when wintergreen oil is used orally.
Ingesting as little as 4 mL can be lethal to children (159). ...when wintergreen oil is used topically in children less than 2 years old (272).
PREGNANCY:
Insufficient reliable information is available; avoid using in amounts greater than those found in foods.
LACTATION: LIKELY UNSAFE
when used orally or topically.
Wintergreen products are likely toxic to nursing infants (19).
Below is general information about the interactions of the known ingredients contained in the product Head Relief. 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, feverfew might have additive effects and increase the risk of bleeding when used with anticoagulant or antiplatelet drugs.
Details
Laboratory research suggests that feverfew may inhibit platelet aggregation (6935,6936,6942,6943,6944,6945,6951). Additionally, in one case report, a 36-year-old patient taking feverfew 2400 mg daily for 3 months experienced vaginal bleeding and a prolonged menstrual cycle, with a modest increase in partial thromboplastin time (PTT) and prothrombin time (PT) (107472).
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Theoretically, feverfew might increase levels of drugs metabolized by CYP1A2.
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Laboratory research shows that feverfew might inhibit CYP1A2 (12479). So far, this interaction has not been reported in humans.
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Theoretically, feverfew might increase levels of drugs metabolized by CYP2C19.
Details
Laboratory research shows that feverfew might inhibit CYP2C19 (12479). So far, this interaction has not been reported in humans.
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Theoretically, feverfew might increase levels of drugs metabolized by CYP2C8.
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Laboratory research shows that feverfew might inhibit CYP2C8 (12479). So far, this interaction has not been reported in humans.
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Theoretically, feverfew might increase levels of drugs metabolized by CYP2C9.
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Laboratory research shows that feverfew might inhibit CYP2C9 (12479). So far, this interaction has not been reported in humans.
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Theoretically, feverfew might increase levels of drugs metabolized by CYP2D6.
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Laboratory research shows that feverfew might inhibit CYP2D6 (12479). So far, this interaction has not been reported in humans.
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Theoretically, feverfew might increase levels of drugs metabolized by CYP3A4.
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Ginger may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs. However, research is conflicting.
Details
Laboratory research suggests that ginger inhibits thromboxane synthetase and decreases platelet aggregation (7622,12634,20321,20322,20323,96257). However, this has not been demonstrated unequivocally in humans, with mixed results from clinical trials (96257). Theoretically, excessive amounts of ginger might increase the risk of bleeding when used with anticoagulant/antiplatelet drugs.
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Theoretically, taking ginger with antidiabetes drugs might increase the risk of hypoglycemia.
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Theoretically, taking ginger with calcium channel blockers might increase the risk of hypotension.
Details
Some animal and in vitro research suggests that ginger has hypotensive and calcium channel-blocking effects (12633). Another animal study shows that concomitant administration of ginger and the calcium channel blocker amlodipine leads to greater reductions in blood pressure when compared with amlodipine alone (107901).
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Theoretically, when taken prior to cyclosporine, ginger might decrease cyclosporine levels.
Details
In an animal model, ginger juice taken 2 hours prior to cyclosporine administration reduced the maximum concentration and area under the curve of cyclosporine by 51% and 40%, respectively. This effect was not observed when ginger juice and cyclosporine were administered at the same time (20401).
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Theoretically, ginger might increase the levels of CYP1A2 substrates.
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In vitro research shows that ginger inhibits CYP1A2 activity (111544). However, this interaction has not been reported in humans.
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Theoretically, ginger might increase the levels of CYP2B6 substrates.
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In vitro research shows that ginger inhibits CYP2B6 activity (111544). However, this interaction has not been reported in humans.
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Theoretically, ginger might increase the levels of CYP2C9 substrates.
Details
In vitro research shows that ginger inhibits CYP2C9 activity (111544). However, this interaction has not been reported in humans.
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Theoretically, ginger might increase the levels of CYP3A4 substrates.
Details
In vitro research shows that ginger inhibits CYP3A4 activity (111544). However, this interaction has not been reported in humans.
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Theoretically, ginger might increase levels of losartan and the risk of hypotension.
Details
In animal research, ginger increased the levels and hypotensive effects of a single dose of losartan (102459). It is not clear if ginger alters the concentration or effects of losartan when taken continuously. Additionally, this interaction has not been shown in humans.
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Theoretically, ginger might increase levels of metronidazole.
Details
In an animal model, ginger increased the absorption and plasma half-life of metronidazole. In addition, the elimination rate and clearance of metronidazole was significantly reduced (20350).
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Ginger may have antiplatelet effects and increase the risk of bleeding if used with nifedipine.
Details
Clinical research shows that combined treatment with ginger 1 gram plus nifedipine 10 mg significantly inhibits platelet aggregation when compared to nifedipine or ginger alone (20324).
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Theoretically, ginger might increase the absorption and blood levels of P-glycoprotein (P-gp) substrates.
Details
In vitro research shows that ginger inhibits drug efflux by P-gp, potentially increasing absorption and serum levels of P-gp substrates (111544).
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Ginger might increase the risk of bleeding with phenprocoumon.
Details
Phenprocoumon, a warfarin-related anticoagulant, might increase the international normalized ratio (INR) when taken with ginger. There is one case report of a 76-year-old woman with a stable INR on phenprocoumon that increased to greater than 10 when she began consuming dried ginger and ginger tea (12880).
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Ginger might increase the risk of bleeding with warfarin.
Details
Laboratory research suggests that ginger might inhibit thromboxane synthetase and decrease platelet aggregation (7622,12634,20321,20322,20323). In one case report, ginger increased the INR when taken with phenprocoumon, which has similar pharmacological effects as warfarin (12880). In another case report, ginger increased the INR when taken with a combination of warfarin, hydrochlorothiazide, and acetaminophen (20349). A longitudinal analysis suggests that taking ginger increases the risk of bleeding in patients taking warfarin for at least 4 months (20348). However, research in healthy people suggests that ginger has no effect on INR, or the pharmacokinetics or pharmacodynamics of warfarin (12881,15176). Until more is known, monitor INRs closely in patients taking large amounts of ginger.
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Combining kava with alcohol may increase the risk of sedation and/or hepatotoxicity.
Details
Kava has CNS depressant effects (11373,18316). Concomitant use of kava with other CNS depressants can increase the risk of drowsiness and motor reflex depression (2093,2098). Additionally, kava has been associated with over 100 cases of hepatotoxicity. There is some concern that kava can adversely affect the liver, especially when used in combination with hepatotoxic drugs (7024,7068,7086,7096,17086,57346). Clinical practice guidelines from a joint taskforce of the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) recommend that alcohol not be used with kava (110318). |
Combining kava with CNS depressants can have additive sedative effects.
Details
Kava has CNS depressant effects (11373,18316). Concomitant use of kava with other CNS depressants can increase the risk of drowsiness and motor reflex depression (2093,2098). Clinical practice guidelines from a joint taskforce of the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) recommend that CNS depressants, including alcohol and benzodiazepines, not be used with kava (110318).
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It is unclear if kava inhibits CYP1A2; research is conflicting.
Details
Although in vitro research and a case report suggest that kava inhibits CYP1A2 (8743,12479,88593), more robust clinical evidence shows that kava has no effect on CYP1A2. In a clinical study in healthy volunteers, taking kava 1000 mg twice daily (containing a daily dose of 138 mg kavalactones) for 28 days had no effect on CYP1A2 activity (13536,98979).
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Theoretically, kava might increase levels of CYP2C19 substrates.
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Theoretically, kava might increase levels of CYP2C9 substrates.
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It is unclear if kava inhibits CYP1A2; research is conflicting.
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Kava might increase levels of CYP2E1 substrates.
Details
In a clinical study in healthy volunteers, taking kava 1000 mg twice daily (containing a daily dose of 138 mg kavalactones) for 28 days inhibited the metabolism of CYP2E1 substrates (13536).
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It is unclear if kava inhibits CYP3AA; research is conflicting.
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Although in vitro research suggests that kava inhibits CYP3A4 (8743,12479), more robust clinical evidence shows that kava has no effect on CYP3A4. In a clinical study in healthy volunteers, taking kava 1000 mg twice daily (containing a daily dose of 138 mg kavalactones) for 28 days had no effect on CYP3A4 activity (13536,98979).
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Combining kava and haloperidol might increase the risk of cardiovascular adverse effects and hypoxia.
Details
Atrial flutter and hypoxia has been reported for a patient who received intramuscular injections of haloperidol and lorazepam after using kava orally. The side effects were attributed to kava-induced inhibition of CYP2D6, but might also have been related to additive adverse effects with the concomitant use of haloperidol, lorazepam, and kava (88593).
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Theoretically, using kava with hepatotoxic drugs might increase the risk of liver damage.
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It is unclear if kava inhibits P-glycoprotein (P-gp); research is conflicting.
Details
In vitro research shows that kava can inhibit P-gp efflux (15131). However, a clinical study in healthy volunteers shows that taking kava standardized to provide 225 mg kavalactones daily for 14 days does not affect the pharmacokinetics of digoxin, a P-gp substrate (15132,98979). It is possible that the use of other P-gp substrates or higher doses of kava might still inhibit P-gp.
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Taking kava with ropinirole might increase the risk for dopaminergic toxicity.
Details
A case of visual hallucinations and paranoid delusions has been reported for a patient who used kava in combination with ropinirole. The adverse effects were attributed to kava-induced inhibition of CYP1A2, which may have reduced the metabolism of ropinirole, resulting in excessive dopaminergic stimulation (88593).
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Theoretically, meadowsweet might have an additive effect with other salicylate-containing drugs, such as aspirin.
Details
Meadowsweet contains salicin, a plant salicylate; however, salicin doesn't seem to have the antiplatelet effects of aspirin (12).
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Theoretically, meadowsweet might have an additive effect with other salicylate-containing drugs, such as choline magnesium trisalicylate (12).
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Meadowsweet contains salicin, a plant salicylate (12).
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Theoretically, meadowsweet might have an additive effect with other salicylate-containing drugs such as salsalate (12).
Details
Meadowsweet contains salicin, a plant salicylate (12).
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Theoretically, willow bark might result in additive adverse effects associated with acetazolamide.
Details
Willow bark contains salicin, a plant salicylate. Human case reports suggests that a combination of acetazolamide and salicylate increases unbound plasma levels of acetazolamide, as well as adverse effects related to acetazolamide (86481).
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Theoretically, willow bark might increase the risk of bleeding when taken with anticoagulant/antiplatelet drugs.
Details
Willow bark has antiplatelet effects, but less so than aspirin (12810).
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Theoretically, willow bark might increase the effects and adverse effects of aspirin.
Details
Willow bark contains salicin, a plant salicylate. It might have an additive effect when taken with other salicylate-containing drugs such as aspirin (12808).
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Theoretically, willow bark might increase the effects and adverse effects of choline magnesium trisalicylate.
Details
Willow bark contains salicin, a plant salicylate. It might have an additive effect when taken with other salicylate-containing drugs such as choline magnesium trisalicylate (12808).
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Theoretically, willow bark might increase the effects and adverse effects of salsalate.
Details
Willow bark contains salicin, a plant salicylate. It might have an additive effect when taken with other salicylate-containing drugs such as salsalate (12808).
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Using wintergreen oil topically in large amounts, with occlusive dressings, or for prolonged periods of time might increase the risk of additive salicylate toxicity when used with aspirin.
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Using wintergreen oil topically might increase the effects and adverse effects of warfarin.
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Several case reports show that concomitant use of topical wintergreen oil-containing products and warfarin can increase INR and bleeding risk due to systemic absorption of the methyl salicylate contained in wintergreen oil (3811,6181). Topical analgesic gels, lotions, creams, ointments, liniments, and sprays can contain up to 55% methyl salicylate (6181).
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Below is general information about the adverse effects of the known ingredients contained in the product Head Relief. 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, feverfew is generally well tolerated.
Chewing fresh feverfew leaves is more likely to cause mouth ulceration and other adverse effects of the mouth, lips, and tongue when compared with commercial feverfew preparations.
Most Common Adverse Effects:
Orally: Abdominal pain, bloating, constipation, diarrhea, flatulence, heartburn, and nausea. Skin rash may occur in sensitive individuals.
Topically: Dermatitis in sensitive individuals.
Cardiovascular ...Orally, feverfew has been associated with palpitations in one patient in a clinical study (6959).
Dermatologic ...Orally, feverfew can cause skin rash (12383). Topically, allergic contact dermatitis can occur (6958,42856,42891). Allergic reactions to feverfew may be more likely in individuals sensitive to the Asteraceae/Compositae family. Members of this family include ragweed, chrysanthemums, marigolds, daisies, and many other herbs.
Gastrointestinal ...Orally, feverfew can cause gastrointestinal symptoms such as heartburn, nausea, diarrhea, constipation, abdominal pain and bloating, and flatulence (6938,6959,12383,22602). Oral numbness has also been reported when feverfew has been taken sublingually in combination with ginger (22602). The traditional method of feverfew administration-chewing fresh feverfew leaves-can result in mouth ulceration, inflamed oral mucosa and tongue, swelling of the lips, and occasionally, loss of taste (6935,6959). Mouth ulceration might result from direct contact with feverfew leaves during chewing, possibly attributable to the sesquiterpene lactone constituent (6959). Some researchers suggest that mouth ulceration is a systemic effect, but one study using dried feverfew capsules reported a higher incidence of mouth ulcers in subjects taking placebo than feverfew (6935,6959,6960).
Genitourinary ...Orally, feverfew has been associated with menstrual changes in one patient in a clinical study (6959) and in one case report involving a 36-year-old patient taking 800 mg of feverfew three times daily for 3 months (107472).
Immunologic ...Orally and topically, feverfew may cause an allergic reaction in individuals sensitive to the Asteraceae/Compositae family. Members of this family include ragweed, chrysanthemums, marigolds, daisies, and many other herbs.
Musculoskeletal ...Orally, feverfew has been associated with joint stiffness in two patients in a clinical study (6959). Discontinuation of oral feverfew after long-term use may cause "post-feverfew syndrome", which includes symptoms such as muscle and joint stiffness (6959,12153).
Neurologic/CNS ...Discontinuation of oral feverfew after long-term use may cause "post-feverfew syndrome", which includes symptoms such as anxiety, headaches, and insomnia (6959,12153).
Other ...Orally, feverfew may cause weight gain (12383).
General
...Orally, ginger is generally well tolerated.
However, higher doses of 5 grams per day increase the risk of side effects and reduce tolerability. Topically, ginger seems to be well tolerated.
Most Common Adverse Effects:
Orally: Abdominal discomfort, burping, diarrhea, heartburn, and a pepper-like irritant effect in the mouth and throat. However, some of these mild symptoms may be reduced by ingesting encapsulated ginger in place of powdered ginger.
Topically: Dermatitis in sensitive individuals.
Cardiovascular ...Orally, use of ginger resulted in mild arrhythmia in one patient in a clinical trial (16306).
Dermatologic
...Orally, ginger can cause hives (17933), as well as bruising and flushing (20316) or rash (20316).
Topically, ginger can cause dermatitis in sensitive individuals (12635,46902).
Gastrointestinal
...Orally, common side effects of ginger include nausea (17933,22602,89898,101761), belching (10380,103359), dry mouth (103359), dry retching (10380), vomiting (10380), burning sensation (10380), oral numbness (22602), abdominal discomfort (5343,89898,96253), heartburn (5343,7624,12472,16306,20316,51845,89894,89895,89898,89899)(101760,101761,101762,111543), diarrhea (5343,101760), constipation (89898,101760,101761), or a transient burning or "chilly hot" sensation of the tongue and throat (52076).
Orally, Number Ten, a specific product composed of rhubarb, ginger, astragalus, red sage, and turmeric, can increase the incidence of loose stools (20346).
Four cases of small bowel obstruction due to ginger bolus have been reported following the ingestion of raw ginger without sufficient mastication (chewing). In each case, the bolus was removed by enterotomy. Ginger is composed of cellulose and therefore is resistant to digestion. It can absorb water, which may cause it to swell and become lodged in narrow areas of the digestive tract (52115).
Genitourinary ...In one clinical trial, some patients reported increased menstrual bleeding while taking a specific ginger extract (Zintoma, Goldaru) 250 mg four times daily orally for 3 days (17931). An "intense" urge to urinate after 30 minutes was reported in two of eight patients given 0.5-1 gram of ginger (7624). However, this effect has not been corroborated elsewhere. Dysuria, flank pain, perineal pain, and urinary stream interruption have been reported in a 43-year-old male who drank ginger tea, containing 2-3 teaspoons of dry ginger, daily over 15 years. The adverse effects persisted for 4 years and were not associated with increases in urinary frequency or urgency. Upon discontinuing ginger, the patient's symptoms began to improve within one week and completely resolved after eight weeks, with no relapses six months later (107902).
Immunologic ...In one case report, a 59-year-old Japanese female with multiple allergic sensitivities developed pruritus and then anaphylactic shock after taking an oral ginger-containing herbal supplement for motion sickness (Keimei Gashinsan, Keimeido). The patient had used this supplement previously for over 20 years with no allergic reaction. The authors theorized the development of a cross-reactivity to ginger after the use of an oral supplement containing zedoary and turmeric, which are also in the Zingiberaceae family (102463).
Neurologic/CNS ...Orally, ginger may cause sedation, drowsiness, or dizziness (16306,17933,51845).
General
...Orally, kava seems to be well tolerated.
Most Common Adverse Effects:
Orally: Drowsiness, dry mouth, dizziness, gastrointestinal upset, headache, memory problems, tremor.
Serious Adverse Effects (Rare):
Orally: There have been over 100 reported cases of hepatotoxicity and a few reported cases of rhabdomyolysis.
Cardiovascular ...Long-term use of very large amounts of kava, especially in high doses (400 mg kava pyrones daily), has been associated with overall poor health including symptoms of low body weight, reduced protein levels, puffy face, hematuria, increased red blood cell volume, decreased platelets and lymphocytes, and possibly pulmonary hypertension (4032,6402). Tachycardia and electrocardiogram (ECG) abnormalities (tall P waves) have been reported in heavy kava users (6402).
Dermatologic ...Orally, kava can cause allergic skin reactions, including sebotropic eruptions, delayed-type hypersensitivity, or urticarial eruption (4032,11370,28489,57277,57325,57343). Chronic use of high doses of kava has also been associated with kava dermopathy, which consists of reddened eyes; dry, scaly, flaky skin; and temporary yellow discoloration of the skin, hair, and nails (6240,6401,8414,8417,11370,28485,57342). This pellagra-like syndrome is unresponsive to niacinamide treatment (6240,7728,11370). The cause is unknown, but may relate to interference with cholesterol metabolism (6240). Kava's adverse effects on liver function might also contribute to kava dermopathy (6401,8417). Kava dermopathy usually occurs within three months to one year of regular kava use, and resolves when the kava dose is decreased or discontinued (6401,8414). Kava dose should be decreased or discontinued if kava dermopathy occurs (6401).
Gastrointestinal ...Orally, kava may cause gastrointestinal upset, nausea, or dry mouth (2093,2094,4032,11370,18316,57228,57343).
Hematologic ...Orally, chronic use of very high doses of kava has been associated with increased red blood cell volume, reduced platelet volume, reduced lymphocyte counts, and reduced serum albumin (6402,57258). Hematuria has also been reported anecdotally (6402).
Hepatic
...Since the early 2000's, hepatotoxicity has been a particular concern with kava.
Worldwide, there have been at least 100 reported cases of hepatotoxicity following use of kava products (7024,7068,7086,7096,11795,17086)(57252,57254,57297). However, some experts question the clinical validity of several of these cases (11369,11371). Some cases were reported multiple times and in some cases it was unlikely that kava was the causative agent (7068,57253).
In susceptible patients, symptoms can show up after as little as 3-4 weeks of kava use. Symptoms include yellowed skin (jaundice), fatigue, and dark urine (7024,7068). Liver function tests can be elevated after 3-8 weeks of use, possibly followed by hepatomegaly and onset of encephalopathy (7024). Kava has also been reported to exacerbate hepatitis in patients with a history of recurrent hepatitis (390). However, in many cases, symptoms seem to resolve spontaneously, and liver function tests usually normalize within eight weeks (390,7068).
Liver toxicity is more frequently associated with prolonged use of very high doses (6401,57346). But there is some concern that even short-term use of kava in typical doses might cause acute hepatitis in some patients, including severe hepatocellular necrosis. The use of kava for as little as 1-3 months has resulted in need for liver transplant and death, although these events are rare (7024,7068,7086,7096,17086).
There is some speculation that the type of extraction method could be responsible for these rare cases of hepatotoxicity (17086). The "Pacific kava paradox" holds that while the alcohol and acetone extracts of kava used for commercial products cause liver toxicity, the traditional kava rhizome preparation mixed with water might not be toxic (11794,17086). However, a more recent analysis reports cases of hepatotoxicity from the aqueous kava extract and suggests that kava's hepatotoxic effects may be due to contaminants such as mold (29676). Other suggested causes of hepatotoxicity include quality of the kava plant, concomitant medications, large doses and prolonged use, and toxic constituents and metabolites of kava (57300,88532).
Some commercial kava extracts contain parts of the stems and other aerial parts in addition to the rhizome, and it has been suggested that a constituent called pipermethysine, which is only found in these aerial parts, might be partly responsible for hepatotoxicity (17086). Other constituents of kava which might contribute to hepatotoxicity are kavalactones, which are metabolized by cytochrome P450 (CYP450) enzymes in the liver. Reactive metabolites are produced which conjugate with glutathione, and might deplete glutathione in a similar manner to acetaminophen (17086). Increased levels of gamma-glutamyl transferase, involved in the production of glutathione, have been reported in chronic kava users (17086). One of the enzymes involved in production of reactive metabolites from kavalactones is cytochrome P450 2E1 (CYP2E1), which is induced by chronic alcohol intake. Alcohol may also compete for other enzymes which clear kavalactone metabolites from the body. This might explain the observation that alcohol ingestion seems to increase the risk of hepatotoxicity with kava (7068,17086).
There is also speculation that "poor metabolizers" or those patients with deficiency in the cytochrome P450 2D6 (CYP2D6) isoenzyme, which occurs in up to 10% of people of European descent, may be at increased risk for hepatotoxic effects from kava (7068). This deficiency has not been found in Pacific Islanders. However, this theory has not been confirmed.
Due to the concerns regarding the potential hepatotoxicity of kava, kava supplements were withdrawn from European and Canadian markets in 2002 (7086). However, many of the market withdrawals of kava have been lifted after re-evaluation of kava suggested that the risk of hepatotoxicity was minimal (91593,91594,91615). Still, clinical practice guidelines from a joint taskforce of the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) recommend exercising caution when using kava in patients with preexisting liver issues (110318). Until more is known, tell patients to use kava cautiously and recommend liver function tests for routine users or those with underlying liver disease.
Immunologic ...Sjögren syndrome has been associated with an herbal supplement containing kava, echinacea, and St. John's wort. Echinacea may have been the primary cause, because Sjögren syndrome is an autoimmune disorder. The role of kava in this syndrome is unclear (10319).
Musculoskeletal
...Kava has been linked with reports of rhabdomyolysis.
A 34-year-old man who consumed kava tea several times a week developed rhabdomyolysis with a peak creatine kinase level of 32,500 units/liter (18212). However, there is speculation that this might have been due to product impurities rather than kava itself. Another case report describes rhabdomyolysis with myoglobinuria and a creatine kinase level of 100,500 units/liter in a 29-year-old man who had taken kava in combination with guarana and ginkgo biloba (18213).
Cases of ataxia and tremors have been reported in patients taking single doses of kava powder 205 grams (11373).
Neurologic/CNS
...Orally, kava may cause headache, dizziness, and drowsiness (4032,6402,11370,11372,11373,18316,112642).
It might also cause extrapyramidal side effects such as involuntary oral and lingual reflexes, twisting movements of the head and trunk, tremors, and other parkinsonian-like symptoms possibly due to dopamine antagonism (534,4055,7727,8415,102086). In one clinical trial, patients taking a kava supplement providing 120 mg of kavalactones twice daily for 16 weeks had a 3.2-fold greater risk of experiencing tremors when compared with patients taking placebo (102086). Theoretically, kava may worsen symptoms in patients with Parkinson disease or precipitate Parkinson-like symptoms in certain patients (4055,7727). Unlike benzodiazepines, kava is not thought to be associated with impaired cognitive function (2097,2098,11373,57332,57333). However, one clinical trial shows that taking a kava supplement providing 120 mg of kavalactones twice daily for 16 weeks increases the risk for memory impairment by 55% when compared with placebo (102086).
Orally, kava may reduce alertness and impair motor coordination in a dose-dependent manner. Some preliminary reports have noted a decline in accuracy of visual attention and slower reaction times after kava ingestion, particularly at higher doses and in combination with alcohol (11373,95926). Population research has also found that ingesting large amounts of kava tea (typically 50 times higher than what is used medicinally in the US) within a 12-hour period before driving increases the odds of being involved in a serious motor vehicle crash resulting in death or serious injury by almost 5-fold when compared to not drinking kava tea (95927). Use of normal doses of kava may also affect the ability to drive or operate machinery, and driving under the influence (DUI) citations have been issued to individuals observed driving erratically after drinking large amounts of kava tea (535). However, in computer-based driving simulator tests, there are no reported adverse effects of kava on performance (95926). Additionally, other research shows that consuming over 4400 mg of kavalactones over a 6-hour kava session does not seem to impair alertness or attention when compared with non-kava drinkers (103867). Similar research using a specific psychometric tool (Brain Gauge) shows that consuming approximately 3680 mg of kavalactones in a 6-hour kava session seems to impair temporal order judgment, which is associated with the brain's ability to track the order of events, when compared with non-kava drinkers. However, it does not seem to impact cognitive domains related to focus, accuracy, timing perception, plasticity, or fatigue when compared with non-kava drinkers (110435).
Ocular/Otic ...Orally, high doses of kava may cause eye irritation (7728). There is one case report of impaired accommodation and convergence, increased pupil diameter, and oculomotor disturbance following a single dose of kava (9920).
Psychiatric ...Apathy has been associated with traditional use of kava at high doses (57313).
Pulmonary/Respiratory ...Orally, kava may cause shortness of breath, possibly due to pulmonary hypertension (6402).
Renal ...Orally, kava may cause acute urinary retention (57349).
General ...Orally, meadowsweet seems to be well tolerated.
Dermatologic ...Meadowsweet contains salicylate constituents. There is insufficient reliable information available to know if the side effects and toxicity normally associated with salicylates could occur with meadowsweet use. Orally, adverse reactions associated with salicin include skin rashes (4).
Gastrointestinal
...Orally, large doses of meadowsweet can cause nausea and other stomach complaints (18).
Meadowsweet contains salicylate constituents. There is insufficient reliable information available to know if the side effects and toxicity normally associated with salicylates could occur with meadowsweet use. Adverse reactions associated with salicylates include gastric irritation, hematochezia, nausea, and vomiting (4).
Immunologic ...Meadowsweet contains salicylate constituents. There is insufficient reliable information available to know if the side effects and toxicity normally associated with salicylates could occur with meadowsweet use. Orally, salicylates can cause hypersensitivity in sensitive individuals (4).
Ocular/Otic ...Meadowsweet contains salicylate constituents. There is insufficient reliable information available to know if the side effects and toxicity normally associated with salicylates could occur with meadowsweet use. Orally, adverse reactions with salicylates include tinnitus (4).
Pulmonary/Respiratory ...Orally, large doses of meadowsweet can cause bronchospastic activity (4).
Renal ...Meadowsweet contains salicylate constituents. There is insufficient reliable information available to know if the side effects and toxicity normally associated with salicylates could occur with the use of meadowsweet. Orally, adverse reactions with salicylates include renal irritation (4).
General
...Orally, willow bark seems to be well tolerated.
Most Common Adverse Effects:
Orally: Diarrhea, dyspepsia, heartburn, and vomiting. May cause itching and rash in sensitive individuals.
Serious Adverse Effects (Rare):
Orally: Gastrointestinal bleeding and renal impairment. May cause serious allergic reactions, including anaphylaxis, in people who are allergic to aspirin.
Cardiovascular ...In one clinical trial, a single patient withdrew from the study investigating oral willow bark due to blood pressure instability that the authors determined was 'possibly' related to treatment (12804).
Dermatologic ...Orally, willow bark may cause itching and rash in some people due to allergy (6456,12474,12475,12804,86459).
Gastrointestinal ...Orally, willow bark extract can cause gastrointestinal adverse effects, but these appear to be less frequent than those caused by NSAIDs. Examples include diarrhea, heartburn, vomiting, and dyspepsia (12474,12475,12804,86459). In a case report of a child, severe gastrointestinal bleeding occurred following use of a specific syrup (FreddoBaby), which contained ribwort plantain, licorice, willow bark, black elder, meadowsweet, and propolis. The adverse effect was attributed to salicylate content of the syrup. This product has since been withdrawn from the market (86477).
Immunologic ...Orally, willow bark may cause serious allergic reactions, including anaphylaxis, in people who are allergic to aspirin (10392)
Neurologic/CNS ...Orally, willow bark may cause headache and dizziness (12804). In a clinical trial evaluating a combination product containing willow bark, black cohosh, sarsaparilla, poplar bark, and guaiac wood (Reumalex), severe headaches occurred (35946).
Ocular/Otic ...Orally, symptoms of allergy to willow bark have included swollen eyes (6456).
Renal ...Salicylates can inhibit prostaglandins, which can reduce renal blood flow (12805). Salicin can cause renal papillary necrosis (12806). The risk for toxicity is greater with high acute doses or chronic use (12805).
General
...Orally, wintergreen leaf seems to be well tolerated, while wintergreen oil may be unsafe.
Topically, wintergreen oil seems to be well tolerated.
Serious Adverse Effects (Rare):
Orally: Salicylate poisoning due to methyl salicylate in wintergreen oil.
Dermatologic ...Wintergreen oil can cause contact dermatitis, which can be irritant or allergic in nature (18,3811,112157). When the oil is applied topically it should not be covered with an occlusive dressing because this could result in absorption of toxic amounts of methyl salicylate (272).
Gastrointestinal ...Orally, wintergreen oil can result in symptoms of salicylate poisoning, including nausea, vomiting, diarrhea, and stomach pain (272). Wintergreen causes gastrointestinal irritation (19).
Neurologic/CNS ...Orally, wintergreen oil can result in symptoms of salicylate poisoning, including headache, tinnitus, and confusion (272).