- Side Effects
- Drug Interactions
- Pregnancy & Breastfeeding
- What Else to Know
Generic Name: sodium acid phosphate
Brand and Other Names: OsmoPrep, Phospho Soda, sodium biphosphate, sodium phosphate, Visicol
Drug Class: Laxatives, Saline
What is sodium acid phosphate, and what is it used for?
Sodium acid phosphate is a medication used to clear the bowels before a colonoscopy procedure.
Sodium acid phosphate may be administered orally as solutions or tablets prior to colonoscopy, or rectally as an enema for short-term treatment of constipation. Sodium acid phosphate may also be administered as part of intravenous (IV) fluids for parenteral nutrition or to supplement phosphate in patients with low phosphate levels (hypophosphatemia).
Sodium acid phosphate is a saline laxative that draws water into the intestines and promotes contractions (peristalsis) that moves the bowel contents. The sodium in the formulation has an osmotic effect that draws a large amount of water into the intestines, causing diarrhea and effectively clearing the colon in preparation for a colonoscopy. Phosphorous in the formulation plays several roles in the body including bone deposition, calcium metabolism, utilization of B complex vitamins, and as a buffer in acid-base equilibrium.
Uses of sodium acid phosphate include:
- Do not use in patients hypersensitive to sodium acid phosphate or any of the components in the formulation.
- There are rare reports of phosphate-related kidney injury (acute phosphate nephropathy) with oral sodium phosphate products used to prepare for a colonoscopy procedure, in some cases resulting in permanent kidney damage with the need for dialysis. Use with caution in such patients and ensure adequate hydration. Risk factors include:
- Do not use IV preparation in patients with
- High phosphate levels (hyperphosphatemia)
- High sodium levels (hypernatremia)
- Low calcium levels (hypocalcemia)
- Do not use oral formulation in patients with:
- Bowel obstruction
- Bowel perforation
- Gastric bypass
- Toxic colitis
- Toxic megacolon
- Acute phosphate nephropathy
- Do not use sodium acid phosphate enema in patients with:
- Do not readminister sodium acid phosphate for at least 7 days after a course.
- Sodium acid phosphate can cause mucosal ulcerations, and there are some reports of colon inflammation with reduced blood flow (ischemic colitis).
- There have been reports of irregular heart rhythm conditions (arrhythmias) including QT interval prolongation.
- Use sodium acid phosphate with caution in patients with heart failure, arrhythmia, angina, cardiomyopathy, electrolyte disturbances, or a history of seizures.
- Use with caution in gastrointestinal conditions such as gastric retention or hypomotility, severe chronic constipation, colitis, ileus, or chronic inflammatory bowel disease.
- Sodium acid phosphate can lead to electrolyte disturbances and fluid loss. Advise patients to hydrate adequately before, during, and after bowel preparation with sodium acid phosphate.
- Use with caution in patients with impaired gag reflex and patients prone to regurgitation or aspiration and monitor during the administration of sodium phosphate.
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What are the side effects of sodium acid phosphate?
Common side effects of sodium acid phosphate include:
- Abdominal pain
- Mucosal bleeding
- Mucosal ulceration in the colon
- Canker sores (aphthous stomatitis)
- Fainting (syncope)
- Electrolyte disturbances in the blood including:
- Reduced blood volume (hypovolemia)
- Irregular heart rhythms (cardiac arrhythmias)
- Hypersensitivity reactions including:
- Impaired kidney function
- Increase in blood urea nitrogen (BUN)
- Increase in creatinine
- Calcium deposits in kidney (nephrocalcinosis)
- Acute kidney failure
- Kidney injury from phosphate (acute phosphate nephropathy)
- Destruction of kidney tubules (renal tubular necrosis)
Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:
- Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
- Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
- Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
- Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.
This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.
What are the dosages of sodium acid phosphate?
Monobasic Sodium Phosphate Monohydrate/Dibasic Sodium Phosphate Heptahydrate
- (48 g/18 g)/100 mL
- 0.398 g/1.102 g
- (7 g/19 g)/118 mL
Bowel Preparation for Colonoscopy
- OsmoPrep: 4 tablets with 8 oz of water orally every 15 minutes (total 20 tablets) the evening before the procedure, and repeat regimen (12 tablets) the next day 3-5 hours before the procedure
- Visicol: 3 tablets with 8 oz of water orally every 15 minutes (last dose 2 tablets, total 20 tablets) evening before the procedure, and repeat the same regimen the next day 3-5 hours before the procedure
- Aqueous: 30-45 mL (of 48 g Na2HPO4-18 g NaH2PO4/100 mL) orally twice10-12 hours apart; each dose with at least 8 oz liquid; each dose followed by additional minimum 16 oz liquid; 2nd dose at least 3 hours before the procedure
- PR: Administer contents of 4.5 oz enema rectally as a single dose
- PO: Administer 15 mL as a single dose every day; not to exceed 45 mL/day
Bowel Preparation for Colonoscopy
(No Standard Regimen; One Recommended)
- Children below 15 kg: 22.5 mL aqueous orally afternoon and evening before the colonoscopy
- Children 15 kg and above: 45 mL aqueous orally afternoon and evening before the colonoscopy
- Children below 2 years: Safety and efficacy not established
- Children 2-4 years: Administer one-half content of 2.25 oz pediatric enema as a single dose
- Children 4-12 years: Administer contents of 2.25 oz pediatric enema as a single dose
- Children 12 years and above: Administer contents of 4.5 oz enema rectally as a single dose
- Children below 5 years: Safety and efficacy not established
- Children 5-10 years: 7.5 mL as a single dose; not to exceed 7.5 mL/day
- Children 10-12 years: 15 mL as a single dose; not to exceed 15 mL/day
- Children 12 years and above: 15 mL as a single dose every day; not to exceed 45 mL/day
- There have been no reports of sodium acid phosphate overdose.
- Overdose may cause electrolyte disturbances including hyperphosphatemia, hypocalcemia, hypernatremia, or hypokalemia, as well as dehydration and hypovolemia.
- Severe electrolyte disturbances can lead to irregular heart rhythms, seizures, kidney failure, and death.
- Sodium acid phosphate overdose is treated with symptomatic and supportive care.
What drugs interact with sodium acid phosphate?
Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.
- Severe interactions of sodium acid phosphate include:
- sodium phosphate rectal
- Serious interactions of sodium acid phosphate include:
- baloxavir marboxil
- potassium phosphates, IV
- Moderate interactions of sodium acid phosphate include:
- Sodium acid phosphate has no listed mild interactions with other drugs.
The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.
It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.
Pregnancy and breastfeeding
- No animal or human reproductive studies have been conducted and it is not known if sodium acid phosphate can cause fetal harm if used during pregnancy. Use sodium acid phosphate in pregnant women only if clearly needed and maternal benefits outweigh potential fetal risks.
- Phosphorus, sodium, and potassium are normal constituents of human breast milk, however, it is not known how sodium acid phosphate alters the levels of these electrolytes. Use with caution in nursing mothers.
What else should I know about sodium acid phosphate?
- Take sodium acid phosphate exactly as prescribed.
- Sodium acid phosphate causes fluid loss. Drink adequate fluids before, during and after taking sodium acid phosphate preparation.
- Do not take sodium acid phosphate for at least 7 days after a course. Do not use other laxatives, particularly those containing sodium or phosphate.
- Store sodium acid phosphate safely out of reach of children.
- In case of overdose, seek medical help or contact Poison Control.
Sodium acid phosphate is a medication used to clear the bowels before a colonoscopy procedure. Common side effects of sodium acid phosphate include bloating, abdominal pain, nausea, vomiting, mucosal bleeding, mucosal ulceration in the colon, canker sores (aphthous stomatitis), headache, dizziness, lightheadedness, fainting (syncope), electrolyte disturbances in the blood, and others. Use with caution in pregnant and breastfeeding women.
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