Sodium Phosphates

Pronunciation

(SOW dee um FOS fates)

U.S. Brand Names

Fleet® Enema [OTC]; Fleet® Phospho®-Soda [OTC]; Fleet® Phospho-Soda® Accu-Prep™ [OTC]; Visicol™

Generic Available

Yes: Enema, injection

Canadian Brand Names

Fleet Enema®; Fleet® Phospho®-Soda Oral Laxative

Use

Oral, rectal: Short-term treatment of constipation and to evacuate the colon for rectal and bowel exams

I.V.: Source of phosphate in large volume I.V. fluids and parenteral nutrition; treatment and prevention of hypophosphatemia

Pregnancy Risk Factor

Pregnancy Implications

Reproduction studies have not been conducted. Use with caution in pregnant women.

Lactation

Use caution in nursing women.

Contraindications

Hypersensitivity to sodium phosphate salts or any component of the formulation; congenital megacolon, toxic megacolon, bowel obstruction, bowel perforation, imperforate anus (enema), congestive heart failure, ascites

Additional product-specific contraindications:

Intravenous phosphate preparation: Should not be used in diseases with high phosphate levels, low calcium levels or hypernatremia.

Oral: Should not be used in patients with kidney disease, unstable angina pectoris, gastric retention, ileus, acute obstruction or pseudo-obstruction, severe chronic constipation, acute colitis, or hypomotility syndrome (ie, hypothyroidism, scleroderma). Should not be used in patients on a sodium-restricted diet.

Warnings/Precautions

Use with caution in patients with impaired renal function (oral solution contraindicated), pre-existing electrolyte imbalances (including patients on diuretics which may effect electrolyte levels or dehydration); risk of hypocalcemia, hyperphosphatemia, hypernatremia, and acidosis. If using as a bowel evacuant, correct electrolyte abnormalities before treatment; inadequate fluid intake may lead to excessive fluid loss and hypovolemia. May cause colonic mucosal aphthous ulcerations; use with caution in patients with an acute exacerbation of chronic inflammatory bowel disease, absorption may be enhanced. Use with caution in debilitated patients. Enemas and oral solution are available in pediatric and adult sizes; prescribe by "volume" not "by bottle".

Additional product-specific contraindications:

Enema preparation: Use caution in patients with a colostomy; not for use in children <2 years of age. Enema tips are latex free.

Intravenous preparation: Must be diluted before use; infuse slowly.

Oral solution: Patients receiving >45 mL of oral solution may develop severe electrolyte shifts, even in the absence of medical contraindications.

Tablet preparation: Prolongation of the QT interval has been reported with use of the tablet formulation; use with caution with other medication known to cause this effect; use caution within 3 months of acute myocardial infarction or cardiac surgery. Do not use with other phosphate-containing products, fatalities have been reported. Not for use in patients <18 years of age.

Adverse Reactions

Frequency not defined.

Cardiovascular: Edema, hypotension

Central nervous system: Dizziness, headache

Endocrine & metabolic: Hypocalcemia, hypernatremia, hyperphosphatemia, calcium phosphate precipitation

Gastrointestinal: Nausea, vomiting, diarrhea, abdominal bloating, abdominal pain, mucosal bleeding, superficial mucosal ulcerations

Renal: Acute renal failure

Postmarketing and/or case reports: Tablet: Atrial fibrillation following severe vomiting

Overdosage/Toxicology

Overdose may lead to cardiac arrhythmias, severe electrolyte disturbances, including hyperphosphatemia, hypocalcemia, hypernatremia or hypokalemia. Treat symptomatically.

Drug Interactions

Antacids: Do not give with magnesium- and aluminum-containing antacids which can bind with phosphate.

Bisphosphonates: Increased risk of hypoglycemia with concurrent use.

Sucralfate: Do not give with sucralfate which can bind with phosphate.

Oral preparations: May affect absorption of other medications due to rapid intestinal peristalsis and watery diarrhea caused by agent

Intravenous preparation: Use caution with thiazide diuretics, may lead to renal damage

Stability

Phosphate salts may precipitate when mixed with calcium salts; solubility is improved in amino acid parenteral nutrition solutions; check with a pharmacist to determine compatibility

Compatibility

Y-site administration: Compatible: Gatifloxacin. Incompatible: Ciprofloxacin. Variable (consult detailed reference): TPN

Compatibility when admixed: Variable (consult detailed reference): Calcium chloride, calcium gluconate, ciprofloxacin

Mechanism of Action

As a laxative, exerts osmotic effect in the small intestine by drawing water into the lumen of the gut, producing distention and promoting peristalsis and evacuation of the bowel; phosphorous participates in bone deposition, calcium metabolism, utilization of B complex vitamins, and as a buffer in acid-base equilibrium

Pharmacodynamics/Kinetics

Onset of action: Cathartic: 3-6 hours; Rectal: 2-5 minutes

Absorption: Oral: ~1% to 20%

Dosage

Normal requirements elemental phosphorus: Oral:

0-6 months: Adequate intake: 100 mg/day

6-12 months: Adequate intake: 275 mg/day

1-3 years: RDA: 460 mg

4-8 years: RDA: 500 mg

9-18 years: RDA: 1250 mg

19 years: RDA: 700 mg

Hypophosphatemia: It is difficult to provide concrete guidelines for the treatment of severe hypophosphatemia because the extent of total body deficits and response to therapy are difficult to predict. Aggressive doses of phosphate may result in a transient serum elevation followed by redistribution into intracellular compartments or bone tissue. Intermittent I.V. infusion should be reserved for severe depletion situations (<1 mg/dL in adults); large doses of oral phosphate may cause diarrhea and intestinal absorption may be unreliable. I.V. solutions should be infused slowly. Use caution when mixing with calcium and magnesium, precipitate may form. The following dosages are empiric guidelines. Note: 1 mmol phosphate = 31 mg phosphorus; 1 mg phosphorus = 0.032 mmol phosphate

Hypophosphatemia treatment: Doses listed as mmol of phosphate:

Intermittent I.V. infusion: Acute repletion or replacement:

Children:

Low dose: 0.08 mmol/kg over 6 hours; use if losses are recent and uncomplicated

Intermediate dose: 0.16-0.24 mmol/kg over 4-6 hours; use if serum phosphorus level 0.5-1 mg/dL

High dose: 0.36 mmol/kg over 6 hours; use if serum phosphorus <0.5 mg/dL

Adults: Varying dosages: 0.15-0.3 mmol/kg/dose over 12 hours; may repeat as needed to achieve desired serum level or

15 mmol/dose over 2 hours; use if serum phosphorus <2 mg/dL or

Low dose: 0.16 mmol/kg over 4-6 hours; use if serum phosphorus level 2.3-3 mg/dL

Intermediate dose: 0.32 mmol/kg over 4-6 hours; use if serum phosphorus level 1.6-2.2 mg/dL

High dose: 0.64 mmol/kg over 8-12 hours; use if serum phosphorus <1.5 mg/dL

Oral: Adults: 0.5-1 g elemental phosphorus 2-3 times/day may be used when serum phosphorus level is 1-2.5 mg/dL

Maintenance: Doses listed as mmol of phosphate:

Children:

Oral: 2-3 mmol/kg/day in divided doses

I.V.: 0.5-1.5 mmol/kg/day

Adults:

Oral: 50-150 mmol/day in divided doses

I.V.: 50-70 mmol/day

Laxative (Fleet®): Rectal:

Children 2-<5 years: One-half contents of one 2.25 oz pediatric enema

Children 5-12 years: Contents of one 2.25 oz pediatric enema, may repeat

Children 12 years and Adults: Contents of one 4.5 oz enema as a single dose, may repeat

Laxative (Fleet® Phospho®-Soda): Oral: Take on an empty stomach; dilute dose with 4 ounces cool water, then follow dose with 8 ounces water; do not repeat dose within 24 hours

Children 5-9 years: 5-10 mL as a single dose

Children 10-12 years: 10-20 mL as a single dose

Children 12 years and Adults: 20-45 mL as a single dose

Bowel cleansing prior to colonoscopy: Adults:

Fleet® Phospho-Soda® Accu-Prep™: Oral: Prior to procedure (timing of doses determined by prescriber): One dose is equal to 45 mL (2 doses are recommended): Each dose is diluted as follows:

Mix 45 mL with 120 mL clear liquid; drink, then follow with at least 240 mL of clear liquid; or

Mix 15 mL with 240 mL clear liquid; drink, then follow with 240 mL clear liquid; repeat every 10 minutes for a total of 45 mL

Visicol™: Oral: Adults: A total of 40 tablets divided as follows:

Evening before colonoscopy: 3 tablets every 15 minutes for 6 doses, then 2 additional tablets in 15 minutes (total of 20 tablets)

3-5 hours prior to colonoscopy: 3 tablets every 15 minutes for 6 doses, then 2 additional tablets in 15 minutes (total of 20 tablets)

Note: Each dose should be taken with a minimum of 8 ounces of clear liquids. Do not repeat treatment within 7 days. Do not use additional agents, especially sodium phosphate products.

Dosage adjustment in renal impairment: Use with caution; ionized inorganic phosphate is excreted by the kidneys; oral solution is contraindicated in patients with kidney disease

Dosage adjustment in hepatic impairment: Not expected to be metabolized in the liver

Elderly: Use with caution due to increased risk of renal impairment in the elderly

Administration

For intermittent I.V. infusion, dilute at a maximum concentration of 0.12 mmol/mL and infuse over 4-6 hours; maximum, rate of infusion: 0.06 mmol/kg/hour

Monitoring Parameters

I.V.: Serum calcium and phosphate levels; renal function

Oral solution: Patients receiving >45 mL of oral solution may develop severe electrolyte shifts, even in the absence of medical contraindications.

Dietary Considerations

Should be taken on an empty stomach with water; a clear liquid diet should be used for 12 hours prior to tablet administration.

Oral solution contains 556 mg (24.17 mEq) sodium/ 5 mL

Whole cow's milk: 0.29 mmol/mL phosphate; 0.025 mEq/mL sodium; 0.035 mEq/mL potassium

Patient Education

May cause diarrhea with the oral preparation; excessive or prolonged use as a laxative may cause dependence. Do not use over-the-counter laxatives when you are nauseated, vomiting, or have abdominal pain, unless directed to by prescriber. Do not use recommended dose more than once in 24 hours. In general, laxative products should not be used for longer than 1 week, unless under guidance of prescriber. Do not use with other laxative products, especially those containing phosphate. Pregnancy/breast-feeding precautions: Inform prescriber if you are or intend to become pregnant. Consult prescriber if breast-feeding.

Enemas: Not for oral use. Insert bottle gently into rectum with tip of bottle pointed towards naval; do not force. Squeeze bottle to expel liquid, stop if resistance is felt. Contact prescriber immediately if no liquid is returned following administration, or if rectal bleeding occurs.

Tablets: Undigested or partially-digested tablets of this or other medications may be seen in stool. Take each dose with 8 oz of clear liquids.

Nursing Implications

Maintain adequate fluid intake

Pediatric enema: When one-half bottle is prescribed, prepare enema by unscrewing cap and removing 2 tablespoons liquid, replace cap, and administer.

Tablets: Undigested or partially-digested tablets of this or other medications may be seen in stool; not for use with other laxatives, especially those containing phosphate

Dental Health: Effects on Dental Treatment

No significant effects or complications reported

Dental Health: Vasoconstrictor/Local Anesthetic Precautions

No information available to require special precautions

Dosage Forms

Enema: Monobasic sodium phosphate 19 g and dibasic sodium phosphate 7 g per 118 mL delivered dose (135 mL)

Fleet® Enema: Monobasic sodium phosphate 19 g and dibasic sodium phosphate 7 g per 118 mL delivered dose (135 mL)

Fleet® Enema for Children: Monobasic sodium phosphate 9.5 g and dibasic sodium phosphate 3.5 g per 59 mL delivered dose (68 mL)

Injection, solution [preservative free]: Phosphate 3 mmol and sodium 4 mEq per mL (5 mL, 15 mL, 50 mL)

Solution, oral:

Fleet® Phospho®-Soda: Monobasic sodium phosphate monohydrate 2.4 g and dibasic sodium phosphate heptahydrate 0.9 g per 5 mL (45 mL, 90 mL) [contains sodium benzoate; unflavored or ginger-lemon flavor]

Fleet® Phospho-Soda® Accu-Prep™ [kit]: Monobasic sodium phosphate monohydrate 2.4 g and dibasic sodium phosphate heptahydrate 0.9 g per 5 mL (15 mL) [solution contains sodium benzoate; kit contains solution in six 15 mL unit-dose containers (equal to two 45 mL doses) plus 4 anorectal pads containing pramoxine hydrochloride 1% and glycerin 12%]

Tablet, oral (Visicol™): Sodium phosphate monobasic monohydrate 1.102 g and sodium phosphate dibasic anhydrous 0.398 g [1.5 g total sodium phosphate per tablet]

References

Clark CL, Sacks GS, Dickerson RN, et al, "Treatment of Hypophosphatemia in Patients Receiving Specialized Nutrition Support Using a Graduated Dosing Scheme: Results From a Prospective Clinical Trial," Crit Care Med , 1995, 23(9):1504-11.

Dickerson R, "Treating Hypophosphatemia," Hosp Pharm , 1985, 20:920-24.

"Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine," National Academy of Sciences, Washington, DC: National Academy Press, 1997.

Food and Drug Administration, Science Background, "Safety of Sodium Phosphates Oral Solution." Available at: http://www.fda.gov/cder/drug/safety/sodiumphospate.htm. Accessed November 6, 2001.

Lentz RD, Brown BM, and Kjellstrand CM, "Treatment of Severe Hypophosphatemia," Ann Intern Med , 1978, 89(6):941-4.

Lloyd CW and Johnson CE, "Management of Hypophosphatemia," Clin Pharm , 1988, 7(2):123-8.

Physician's Desk Reference , 54th ed, Montvale, NJ: Medical Economics Co, 2000.

Rosen GH, Boullata JI, O'Rangers EA, et al, "Intravenous Phosphate Repletion Regimen for Critically Ill Patients With Moderate Hypophosphatemia," Crit Care Med , 1995, 23(7):1204-10.

"Safe Practices for Parenteral Nutrition Formulations," National Advisory Group on Standards and Practice Guidelines for Parenteral Nutrition, J Parenter Enteral Nutr , 1998, 22(2):49-66.

Dagago, JS, "Chapter 24: Mineral and Metabolic Bone Disease," Washington Manual of Therapeutics , 29th ed, Carey CF and Schaiff R, eds, Philadelphia, PA: Lippincott-Raven, 1998.

International Brand Names

Fleet Enema® (CA); Fleet® Phospho®-Soda Oral Laxative (CA)

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