Enema by H.J. Sutton Industries Ltd.

EFFECTIVE

• Bowel preparation. Oral sodium phosphate is effective for cleansing the colon in preparation for colonoscopy; however, it is unclear whether sodium phosphate is as effective as polyethylene glycol (PEG) solution. Some products are approved by the US Food and Drug Administration (FDA) for this use. However, due to the potential for kidney damage, sodium phosphate is not recommended as first-line therapy. Details: Sodium phosphate tablets (OsmoPrep, Salix Pharmaceuticals; Visicol, Salix Pharmaceuticals) are FDA-approved for cleansing the colon in preparation for colonoscopy. Clinical research shows that using the OsmoPrep formulation can achieve an "excellent" or "good" response rate, which is defined as having 90% of the mucosa visible with only some or little suctioning needed, in 94% to 97% of patients (88133). Similarly, using the specific product Visicol has been shown to achieve an excellent or good response rate in 82% to 86% of patients (94674). Non-FDA-approved sodium phosphate products have also been investigated. One such product (Fleet Phospho-soda, C. B. Fleet Co.) has been shown to achieve adequate bowel cleansing in 23% to 89% of patients (93846,94673). Another sodium phosphate tablet preparation (Clicolon tablets, Korea Pharma Co.) has been shown to achieve adequate bowel cleansing in 63% to 93% of patients (93848,93850,93853). Excellent or good bowel cleansing was found in 98.6% of patients using a 32-tablet regimen of other sodium phosphate tablets (Quiklean, Universal Integrated Corporation) (107008). Reasons for the differences in the percentage of patients who achieve adequate bowel cleansing with the same sodium phosphate product may relate to the method used to analyze bowel cleansing, differences in diet followed during bowel cleansing, and demographic factors (93846,93848,93850,93853). Various preparations (OsmoPrep, Salix Pharmaceuticals; Visicol, Salix Pharmaceuticals; Clicolon tablets, Korea Pharma Co.; Quiklean, Universal Integrated Corporation) have been used which contain 1.102 grams of sodium phosphate monobasic monohydrate and 0.398 grams of sodium phosphate dibasic anhydrous. These products have been taken as 3-4 tablets with 8 ounces of water every 15 minutes for a total of 20 tablets the evening before colonoscopy, and 3-4 tablets with 8 ounces of water every 15 minutes for a total of 12-20 tablets the morning of a colonoscopy (88133,93848,93850,94674,107008). Also, sodium phosphate solution (Fleet Phospho-soda, C. B. Fleet Co.) containing sodium hydrogen phosphate 24.4 grams and disodium phosphate dodecahydrate 10.8 grams has also been used the morning and evening before the procedure (93846). Numerous publications have compared the bowel cleansing activity of sodium phosphate with PEG solution. When given as a split-overnight dosage, sodium phosphate is about as effective as PEG solutions in achieving adequate bowel cleansing. However, when day-before dosage is used, PEG is more effective for bowel cleansing than sodium phosphate (93861,93862,107008). Sodium phosphate and PEG may have different effectiveness depending on the colonic site assessed. When only trials assessing descending colon cleansing are considered, sodium phosphate is found to work similarly to PEG solutions. When only studies assessing ascending colon cleansing are considered, PEG is more effective for bowel cleansing than sodium phosphate (93861). Also, a large clinical trial in outpatients scheduled for non-sedated colonoscopy shows that receiving PEG resulted in an easier insertion and a less painful colonoscopy when compared with receiving sodium phosphate (104473). However, in patients with chronic constipation, sodium phosphate seems to be preferable. A meta-analysis of three small clinical studies in adults with chronic constipation shows that using sodium phosphate has an 87% greater chance of a successful bowel preparation when compared with using PEG (104472). Sodium phosphate is not recommended as first-line therapy for bowel preparation prior to colonoscopy due to the potential for kidney damage (93863,94672). In fact, one sodium phosphate preparation (Fleet Phospho-soda, C. B. Fleet Co.) that was previously approved as an over-the-counter supplement for bowel preparation in the US was withdrawn from the market for this indication in December 2008 due to concerns for phosphate-induced kidney disease (94672). Of the sodium phosphate products that are still approved by the FDA, current guidelines recommend that these products not be used for bowel cleansing in patients with kidney disease, pre-existing electrolyte disturbances, congestive heart failure, cirrhosis, ascites, or inflammatory bowel disease. Guidelines also recommend that caution should be used if these products are prescribed for patients who are elderly, hypertensive, or taking certain classes of drugs (94672). For small bowel preparation for endoscopy, a meta-analysis suggests that sodium phosphate is no more effective than fasting alone (93860).
• Hypophosphatemia. Oral or intravenous phosphate salts are effective for the prevention or treatment of hypophosphatemia. Some products are approved by the US Food and Drug Administration (FDA) for this use. Details: Taking sodium or potassium phosphate orally is effective for preventing and treating hypophosphatemia (15). Treating hypophosphatemia with oral phosphates requires monitoring of serum electrolyte levels to determine appropriate dosing (15). The FDA-approved intravenous (IV) product is also used for the correction of hypophosphatemia (8302,8303,88135). FDA-approved intravenous (IV) sodium phosphate or potassium phosphate 15-30 mmol is typically given over 2-12 hours. Higher doses have been used if needed to increase efficacy (8302,8303,88135).

LIKELY EFFECTIVE

• Constipation. Oral or rectal sodium phosphate is approved by the US Food and Drug Administration (FDA) as an ingredient in over-the-counter (OTC) products to treat constipation. Details: Sodium phosphate is an FDA-permitted ingredient of oral and rectal OTC products intended for the treatment of constipation (88107).
• Dyspepsia. Oral aluminum phosphate and calcium phosphate are approved by the US Food and Drug Administration (FDA) as ingredients in over-the-counter (OTC) antacids. Details: Aluminum phosphate and calcium phosphate are FDA-permitted ingredients of oral OTC products intended for use as antacids (88107).
• Hypercalcemia. Although other treatments are preferred, oral non-calcium phosphate salts are beneficial for treatment of mild to moderate hypercalcemia. Details: Taking phosphate salts (except calcium phosphate) orally is effective for treating mild to moderate hypercalcemia (88144,88145). Treating hypercalcemia with oral phosphates requires monitoring of serum electrolyte levels to determine appropriate dosing (15); other agents are now preferred (6479). Intravenous phosphates should be avoided due to the risk of calcium precipitation in vital organs (metastatic calcification) (15,88144,88145).

POSSIBLY EFFECTIVE

• Kidney stones (nephrolithiasis). Oral potassium phosphate seems to be beneficial for prevention of kidney stones in individuals with hypercalciuria. Details: Taking potassium phosphate orally may help prevent calcium oxalate kidney stones in patients with hypercalciuria (6470). Clinical research in adults with absorptive hypercalciuria and at high risk for stone formation shows that taking a specific slow-release potassium phosphate product (Uro-Phos-K, Mission Pharmacal), providing phosphate 620 mg orally twice daily for 4 days, reduces urinary calcium excretion by 35% to 40% (2208,2209). Potassium and sodium phosphate salts providing 1200-1500 mg of elemental phosphate daily have been used (2209,6470).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Athletic performance. The evidence is mixed as to whether oral sodium phosphate improves cycling or running performance. Most research suggests that oral calcium phosphate and potassium phosphate are not beneficial. Details: Clinical research shows that taking calcium phosphate or potassium phosphate orally does not improve running or cycling performance (2499,9300,8301). Evidence for the use of sodium phosphate to improve cycling performance is mixed. One very small clinical study shows that taking sodium phosphate as tribasic sodium phosphate dodecahydrate for 6 days before a 10-mile cycling trial increases mean power output by about 10% and decreases the time needed to complete the trial by 3% in trained male cyclists (88150). Other small clinical trials in trained cyclists show that taking the same form of sodium phosphate as 50 mg/kg of fat-free mass in four divided doses daily for 6 days modestly improves work, power output, and peak oxygen uptake and reduces heart rate during high-intensity cycling exercise when compared to baseline (93857,93858,93859,107007). However, conflicting research shows that taking a similar dosage of this form of sodium phosphate does not improve time trial performance, work accomplished relative to energy expenditure, power output, or oxygen uptake in trained cyclists (93855,93856,107007). Sodium phosphate has also been evaluated for improving running performance, with mixed findings. Two small clinical trials in female athletes show that tribasic sodium phosphate dodecahydrate 50 mg/kg of fat-free mass taken in four divided doses daily for 6 days moderately improves repeated sprint times when compared with placebo (93843,93844). However, taking the same dosage does not significantly improve sprint times in male athletes (93849). Also, sodium phosphate does not seem to improve endurance or aerobic capacity in treadmill tests (8301,93854). Reasons for the discrepancies regarding the effects of sodium phosphate on athletic performance are not entirely clear, but likely relate to the very small number of participants in the included trials.
• Diabetic ketoacidosis. Potassium phosphate infusion is not recommended as first-line therapy for adults with diabetic ketoacidosis. Details: Clinical research shows that intravenous infusion of potassium phosphate 8.5 mmol/hour (approximately 6 grams of phosphate over 24 hours) along with potassium chloride 12.5 mEq/hour provides no benefit over potassium chloride alone in adults with diabetic ketoacidosis (88149). Guidelines for the treatment of diabetic ketoacidosis in the both the US and UK do not recommend phosphate replacement for most patients. However, it may be considered in specific cases, such as cardiac dysfunction, anemia, respiratory depression, and serum phosphate concentrations below 1 mg/dL (107349,107350A).
• Osteoporosis. Calcium phosphate seems to be beneficial for bone density improvement; however, it does not seem to be more beneficial than calcium carbonate. Details: In postmenopausal adults with osteoporosis and low phosphate intakes, taking calcium 1800 mg daily as tricalcium phosphate for 12 months improves lumbar spine and hip densities. However, it is no more effective than taking the same amount of calcium as calcium carbonate (93847). The calcium products were used in combination subcutaneous teriparatide and oral vitamin D (cholecalciferol) 1000 IU daily.
• Refeeding syndrome. It is unclear if intravenous potassium phosphate or sodium phosphate is beneficial for prevention of refeeding syndrome. Details: Preliminary clinical research shows that giving intravenous sodium and potassium phosphates, 50 mmol (1.56 grams) phosphate over 24 hours, prevents the refeeding syndrome seen when restarting adequate nutrition after severe malnutrition or starvation when compared with historical controls (88148). More evidence is needed to rate phosphate salts for these uses.

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LIKELY SAFE ...when used orally and appropriately short-term (15). ...when sodium phosphate is used rectally and appropriately, no more than once every 24 hours, short-term (104471). Long-term use or high doses used orally or rectally require monitoring of serum electrolytes (2494,2495,2496,2497,2498,3092,112922). ...when used intravenously. Potassium phosphate is an FDA-approved prescription drug (15).

POSSIBLY UNSAFE ...when phosphate (expressed as phosphorus) intake exceeds the tolerable upper intake level (UL) of 4 grams daily for adults under 70 years and 3 grams daily for adults older than 70. Hyperphosphatemia, resulting in electrolyte disturbances, alterations in calcium homeostasis, and calcification of nonskeletal tissues, may occur (7555). ...when used rectally more frequently than once every 24 hours, in excessive doses, with longer retention enema time, or in older patients with comorbidity or renal impairment (112922). The US Food and Drug Administration (FDA) warns that this may increase the risk of hyperphosphatemia, dehydration, and electrolyte imbalances leading to kidney and heart damage (104471).

CHILDREN: LIKELY SAFE
when used orally and appropriately at recommended dietary allowances (RDAs). The daily RDAs are: children 1-3 years, 460 mg; children 4-8 years, 500 mg; males and females 9-18 years, 1250 mg (7555). ...when sodium phosphate is used rectally and appropriately, no more than once every 24 hours, short-term in children 2 years and older (104471). ...when used intravenously. Intravenous potassium phosphate is an FDA-approved prescription drug (15).

CHILDREN: POSSIBLY UNSAFE
when phosphate (expressed as phosphorus) intake exceeds the tolerable upper intake level (UL) of 3 grams daily for children 1-8 years of age and 4 grams daily for children 9 years and older. Hyperphosphatemia, resulting in electrolyte disturbances, alterations in calcium homeostasis, and calcification of nonskeletal tissues, may occur (7555). ...when sodium phosphate is used rectally more frequently than once every 24 hours, or in children under 2 years of age or with Hirchsprung disease (112922). The US Food and Drug Administration (FDA) warns that these uses may increase the risk of hyperphosphatemia, dehydration, and electrolyte imbalances leading to kidney and heart damage (104471).

PREGNANCY AND LACTATION: LIKELY SAFE
when used orally and appropriately at the recommended dietary allowance (RDA) of 1250 mg daily for individuals 14-18 years of age and 700 mg daily for those over 18 years of age (7555). ...when sodium phosphate is used rectally and appropriately short-term (15). ...when used intravenously. Intravenous potassium phosphate is an FDA-approved prescription drug (15).

PREGNANCY AND LACTATION: POSSIBLY UNSAFE
when phosphate (expressed as phosphorus) intake exceeds the tolerable upper intake level (UL). Hyperphosphatemia, resulting in electrolyte disturbances, alterations in calcium homeostasis, and calcification of nonskeletal tissues, may occur. The UL during pregnancy is 3.5 grams daily. During lactation, the UL is 4 grams daily (7555).

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BISPHOSPHONATES Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, taking phosphate salts with bisphosphonates might increase the risk of hypocalcemia.  Details Combining bisphosphonates and phosphate can cause hypocalcemia. In one report, hypocalcemic tetany developed in a patient taking alendronate (Fosamax) who received a large dose of phosphate salts as a pre-operative laxative (14589).

ERDAFITINIB (Balversa) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Probable •  Level of Evidence = A Taking erdafitinib with phosphate salts increases the risk of hyperphosphatemia.  Details Erdafitinib increases phosphate levels. It is recommended that patients taking erdafitinib restrict phosphate intake to no more than 600-800 mg daily (104470).

FUTIBATINIB (Lytgobi) Interaction Rating = Major Do not take this combination. Severity = High •  Occurrence = Likely •  Level of Evidence = A Taking futibatinib with phosphate salts increases the risk of hyperphosphatemia.  Details Futibatinib can cause hyperphosphatemia, as reported in 88% of patients in clinical studies. In addition, 77% of patients in clinical studies required use of a phosphate binder to manage hyperphosphatemia. Phosphate salts should generally be avoided by people taking this medication (112912).

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General ...Orally, intravenously, and rectally, phosphate salts are generally well tolerated when used appropriately and/or as prescribed.
Most Common Adverse Effects:
Orally: Abdominal pain, anal irritation, bloating, diarrhea, headache, gastrointestinal irritation, hyperphosphatemia, hypocalcemia, malaise, nausea, sleep disturbance, and vomiting.
Rectally: Hyperphosphatemia and hypocalcemia.
Serious Adverse Effects (Rare):
Orally: Extraskeletal calcification.

Cardiovascular ...Orally, a case of allergic acute coronary syndrome e., Kounis syndrome) is reported in a 43-year-old female after ingesting a specific sodium phosphate laxative product (Travad oral). She presented with maculopapular rash that progressed to anaphylaxis and a non-ST elevation acute coronary syndrome. The patient recovered after hospitalization for 3 days with medical management (112894).

Gastrointestinal ...Orally, phosphate salts can cause gastrointestinal irritation, nausea, abdominal pain, bloating, anal irritation, and vomiting (15,2494,2495,2496,2497,93846,93848,93850,93851,93853,107008). Sodium and potassium phosphates can cause diarrhea (15). Aluminum phosphate can cause constipation (15). A large comparative study shows that, when taken orally as a bowel preparation for colonoscopy, sodium phosphate is associated with gastric mucosal lesions in about 4% of patients (93868).

Neurologic/CNS ...Orally, phosphate salts can commonly cause malaise (93846). Headaches and sleep disturbance may also occur (93848,93851).

Renal ...Orally, use of sodium phosphate for bowel cleansing has been associated with an increased risk of acute kidney injury in some patients (93863). However, a pooled analysis of clinical research suggests that results are not consistent for all patients (93864). Some evidence suggests that female gender, probably due to lower body weight, iron-deficiency anemia, dehydration, and chronic kidney disease are all associated with an increased risk of sodium phosphate-induced kidney dysfunction (93865).

Other ...Orally, phosphate salts can cause fluid and electrolyte disturbances including hyperphosphatemia and hypocalcemia, and extraskeletal calcification. Potassium phosphates can cause hyperkalemia. Sodium phosphates can cause hypernatremia and hypokalemia (15,2494,2495,2496,2497,107008).
Rectally, phosphate salts can cause fluid and electrolyte disturbances including hyperphosphatemia and hypocalcemia (15,112922).
Deaths related to intake of oral or rectal phosphate salts are rare and most have occurred in infants and are related to overdose (93866). However, death has also been reported in elderly patients using sodium phosphate enemas, mainly at standard doses of 250 mL (93867).

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