Skip to main content

Saline Laxatives

Class: Cathartics and Laxatives
ATC Class: A06AX02
VA Class: GA200
CAS Number: 124-38-9
Brands: Ceo-Two, Fleet Enema, Fleet Pedia-Lax, OsmoPrep, Phillips' Milk of Magnesia

Warning

    Renal Effects Associated with Oral Sodium Phosphates Preparations
  • Renal failure, acute phosphate nephropathy, and nephrocalcinosis reported rarely with oral sodium phosphates preparations (e.g., oral solution, OsmoPrep tablets) used for bowel cleansing. Often resulted in permanent renal function impairment and sometimes required long-term dialysis. (See Renal Effects under Cautions.)

  • Risk of acute phosphate nephropathy may be increased in patients with increased age (>55 years of age), hypovolemia, increased bowel transit time (e.g., bowel obstruction), active colitis, baseline renal disease, or known or suspected electrolyte disturbances (e.g., dehydration), and in patients receiving drugs that affect renal perfusion or function (e.g., diuretics, ACE inhibitors, angiotensin II receptor antagonists, possibly NSAIAs).

  • Importance of adherence to recommended dosage and dosing regimen.

Introduction

Laxatives containing magnesium cations or phosphate anions.

Uses for Saline Laxatives

Constipation

Used to relieve occasional constipation.

Use of saline laxatives for simple constipation is seldom necessary or desirable; bulk-forming laxatives are drugs of choice.

Do not use rectal suppositories or enemas if oral laxatives are effective.

Mild saline laxatives (e.g., oral magnesium hydroxide, milk of magnesia) have been used to treat constipation during pregnancy or the puerperium; bulk-forming laxatives or stool softeners preferred.

Used rectally, after administration of a stool softener or mineral oil, to evacuate the impacted colon in the treatment of constipation associated with stricture of the colon or fecal impaction. Alternatively, administer phosphate-containing saline enemas rectally after manual disimpaction to promote evacuation of fecal impactions.

Bowel Cleansing

Used orally and/or rectally (as suppositories or enemas) to empty the bowel prior to surgery or radiologic, proctoscopic, or endoscopic procedures, when thorough evacuation is essential.

FDA recommends using oral sodium phosphates preparations for bowel cleansing only when a prescription for such use has been issued by a clinician. (See Renal Effects under Cautions.)

Poisonings

May hasten removal of some poisons from the GI tract after inducing emesis or performing gastric lavage. Not for use after poisonings with ingested acids or alkalies. Magnesium laxatives should not be used to remove poisons that produce CNS depression or renal function impairment.

Saline Laxatives Dosage and Administration

General

    Bowel Cleansing
  • Patients must drink sufficient quantities of clear fluids (minimum of 1.9–3.4 L per regimen, depending on the specific regimen). Use IV hydration in a hospital setting for fragile patients with inadequate home support or who are unable to drink an appropriate fluid volume. (See Fluid Intake under Cautions.)

Administration

Administer magnesium-containing saline laxatives orally as chewable tablets, suspensions, or solutions.

Administer phosphate-containing laxatives orally as solutions or tablets and rectally as enemas. Do not administer commercially available phosphate-containing rectal enema solutions orally.

Administer carbon dioxide-releasing suppositories (e.g., CEO-TWO) rectally.

Select rectal phosphate-containing laxatives carefully to ensure appropriate volume for age to minimize risk of overdosage.

Administer laxatives as infrequently as possible at the lowest effective dosage level. Do not use for >7 days unless directed by prescriber. FDA states that sodium phosphates preparations should not be used for self-medication of occasional constipation for >3 days.

Administer laxatives with sufficient fluids (i.e., 240 mL) to prevent dehydration from repeated administration. (See Fluid Intake under Cautions.)

Oral Administration

Administer orally as magnesium-containing chewable tablets, suspensions, or solutions or as phosphate-containing solutions or tablets. Drink a full (240 mL) glass of clear liquid (e.g., water) following administration of each dose.

Do not administer fixed combination of magnesium hydroxide and mineral oil with meals; typically administered at bedtime.

Shake suspensions well before use.

May refrigerate oral sodium phosphates solutions to improve taste; may drink magnesium citrate chilled.

Use sodium phosphates tablets with caution in patients with impaired gag reflex and those prone to regurgitation or aspiration; observe these patients during administration of tablets.

Reconstitution (Magnesium Sulfate Crystals)

To prepare magnesium sulfate oral solution, dissolve appropriate dose of the crystals in at least 240 mL water; may add lemon juice to mask bitter taste and minimize nausea.

Dilution

Dilute sodium phosphates oral solution prior to administration. When used as a laxative for self-medication of occasional constipation, mix appropriate dose of the solution with 240 mL of cool water.

Rectal Administration

Administer rectally as phosphate-containing enemas or carbon dioxide-releasing suppositories.

Suppositories

Carbon dioxide-releasing suppositories: Remove wrapper and moisten under a warm-water tap for 30 seconds or in a cup of water for ≥10 seconds prior to rectal insertion; do not use mineral oil or petroleum jelly to lubricate.

Insert suppository high into the rectum past the largest diameter of the suppository; retain for as long as possible (usually 5–30 minutes) before defecating.

Enemas

Administer sodium phosphates enema at room temperature. Drink additional liquid during therapy to ensure adequate hydration.

Remove protective shield (if present) from tip of enema.

Before administering, lie on left side with knees bent or kneel on the bed with head and chest lowered and forward until the left side of the face is resting on the surface of the bed.

With steady pressure, insert enema nozzle into rectum, with nozzle pointed toward the navel. To ease insertion, have patient bear down as if having a bowel movement. Squeeze container until nearly all the liquid is expelled. Use caution to avoid bowel perforation. If resistance is encountered during insertion or administration, discontinue procedure to avoid perforation or rectal abrasion.

Retain until definite lower abdominal cramping felt. Complete evacuation of the left colon usually occurs within 1–5 minutes.

Disposable enemas are for single-use only.

For children 2–4 years of age, prepare an enema containing dibasic sodium phosphate 1.75 g and monobasic sodium phosphate 4.75 g in approximately 29 mL for administration as follows. Unscrew the cap of a pediatric-strength enema containing dibasic sodium phosphate 3.5 g and monobasic sodium phosphate 9.5 g in 59 mL (e.g., Fleet Pedia-Lax Enema) and remove 30 mL of solution. Replace the cap and administer the enema as directed.

Dosage

Most studies suggest that the minimum effective oral laxative dose of magnesium is 80 mEq. (See Electrolytic Content under Cautions.)

Magnesium sulfate crystals: Each level teaspoonful of crystals provides approximately 5 g of magnesium sulfate and 495 mg (40.7 mEq) of magnesium.

Sodium phosphates enemas: A 66-mL enema (Fleet Pedia-Lax Enema) delivers a dose of 3.5 g of dibasic sodium phosphate and 9.5 g of monobasic sodium phosphate in 59 mL; a 133-mL enema (Fleet Enema) delivers a dose of 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate in 118 mL; a 230-mL enema (Fleet Enema Extra) delivers a dose of 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate in 197 mL.

Pediatric Patients

Constipation

Laxatives should be used as infrequently as possible, at the lowest effective dosage level, and usually for ≤7 days; laxatives should be used for longer periods only under the management of a clinician and as part of a carefully planned therapeutic regimen. (See Chronic Use or Overdosage under Cautions.)

Magnesium Citrate
Oral

Children 2–5 years of age: For self-medication, 2.7–6.25 g (usually 60–90 mL [3.5–5.25 g] of a 291-mg/5-mL oral solution ) as a single daily dose or in divided doses.

Children 6–11 years of age: For self-medication, 5.5–12.5 g (usually 90–150 mL [5.25–8.75 g] of a 291-mg/5-mL oral solution ) as a single daily dose or in divided doses.

Children ≥12 years of age: For self-medication, 8.75–25 g (usually 150–300 mL [8.75–17.5 g] of a 291-mg/5-mL oral solution ) as a single daily dose or in divided doses.

Magnesium Hydroxide
Oral

Children 2–5 years of age: For self-medication, 0.4–1.2 g daily given as a single dose (preferably at bedtime), in divided doses, or as directed by a clinician.

Children 6–11 years of age: For self-medication, 1.2–2.4 g daily given as a single dose (preferably at bedtime), in divided doses, or as directed by a clinician.

Children ≥12 years of age: For self-medication, 2.4–4.8 g daily given as a single dose (preferably at bedtime), in divided doses, or as directed by a clinician.

Magnesium Sulfate
Oral

Children 2–5 years of age: For self-medication, 2.5–5 g daily given as a single dose or in divided doses.

Children 6–11 years of age: For self-medication, 5–10 g daily given as a single dose or in divided doses.

Children ≥12 years of age: For self-medication, 10–30 g daily given as a single dose or in divided doses.

Fixed Combination of Magnesium Hydroxide and Mineral Oil
Oral

Do not use manufacturer's provided dosage cup for Phillips' M-O for children.

Children 6–11 years of age: For self-medication, 1.2–1.8 g of magnesium hydroxide (20–30 mL of the fixed-combination suspension) daily given as a single dose (at bedtime), in divided doses, or as directed by a clinician.

Children ≥12 years of age: For self-medication, 2.7–3.6 g of magnesium hydroxide (45–60 mL of the fixed-combination suspension) daily given as a single dose (at bedtime), in divided doses, or as directed by a clinician.

Sodium Phosphates Enemas
Rectal

Do not administer adult-size Fleet enemas to children <12 years of age. Do not administer a full 59-mL Fleet Pedia-Lax Enema to children <5 years of age.

Children 2–4 years of age: For self-medication, 1.75 g of dibasic sodium phosphate and 4.75 g of monobasic sodium phosphate (½ bottle [approximately 29 mL] of Fleet Pedia-Lax Enema) given as a single daily dose. To obtain correct dose, remove 30 mL liquid from Fleet Pedia-Lax Enema prior to administration.

Children 5–11 years of age: For self-medication, 3.5 g of dibasic sodium phosphate and 9.5 g of monobasic sodium phosphate (1 bottle [approximately 59 mL] of Fleet Pedia-Lax Enema) given as a single daily dose or as directed by a clinician.

Children ≥12 years of age: For self-medication, 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) given as a single daily dose.

Sodium Phosphates Oral Solution
Oral

Children 5–9 years of age: For self-medication, 1.35 g of dibasic sodium phosphate and 3.6 g of monobasic sodium phosphate given as a single daily dose.

Children ≥10 years of age: For self-medication, 2.7 g of dibasic sodium phosphate and 7.2 g of monobasic sodium phosphate given as a single daily dose.

Carbon Dioxide-releasing Suppositories
Rectal

Children ≥12 years of age: For self-medication, 1 suppository (0.9 g potassium bitartrate and 0.6 g sodium bicarbonate) given as a single daily dose.

Bowel Cleansing

Consult a clinician for details (e.g., time of administration) of the specific regimen to be used to clear the bowel prior to surgical, radiologic, or endoscopic procedures.

Fleet Sodium Phosphates Enemas
Rectal

Do not administer adult-size Fleet enemas to children <12 years of age. Do not administer a full 59-mL Fleet Pedia-Lax Enema to children <5 years of age.

Children 2–4 years of age: For self-medication, 1.75 g of dibasic sodium phosphate and 4.75 g of monobasic sodium phosphate (½ bottle [approximately 29 mL] of Fleet Pedia-Lax Enema) given as a single daily dose. To obtain correct dose, remove 30 mL liquid from Fleet Pedia-Lax Enema prior to administration.

Children 5–11 years of age: For self-medication, 3.5 g of dibasic sodium phosphate and 9.5 g of monobasic sodium phosphate (1 bottle [approximately 59 mL] of Fleet Pedia-Lax Enema) given as a single daily dose or as directed by a clinician.

Children ≥12 years of age: For self-medication, 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) given as a single daily dose.

Adults

Constipation

Laxatives should be used as infrequently as possible, at the lowest effective dosage level, and usually for ≤7 days; laxatives should be used for longer periods only under the management of a clinician and as part of a carefully planned therapeutic regimen. (See Chronic Use or Overdosage under Cautions.)

Magnesium Citrate
Oral

For self-medication: 8.75–25 g (usually 150–300 mL of a 291-mg/5-mL oral solution ) as a single daily dose or in divided doses.

Magnesium Hydroxide
Oral

For self-medication: 2.4–4.8 g daily given as a single dose (preferably at bedtime), in divided doses, or as directed by a clinician.

Magnesium Sulfate
Oral

For self-medication: 10–30 g daily given as a single dose or in divided doses.

Fixed Combination of Magnesium Hydroxide and Mineral Oil
Oral

For self-medication: 2.7–3.6 g of magnesium hydroxide (45–60 mL of the fixed-combination suspension) daily given as a single dose (at bedtime), in divided doses, or as directed by a clinician.

Sodium Phosphates Enemas
Rectal

For self-medication: 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) given as a single daily dose.

Sodium Phosphates Oral Solution
Oral

For self-medication: 2.7 g of dibasic sodium phosphate and 7.2 g of monobasic sodium phosphate given as a single daily dose.

Carbon Dioxide-releasing Suppositories
Rectal

1 suppository (0.9 g potassium bitartrate and 0.6 g sodium bicarbonate) given as a single daily dose.

Bowel Cleansing
Sodium Phosphates Enemas
Rectal

For self-medication: 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) given as a single daily dose.

OsmoPrep Sodium Phosphates Tablets
Oral

Evening before procedure: 1.592 g of dibasic sodium phosphate and 4.408 g of monobasic sodium phosphate (4 tablets) with 240 mL clear liquids; repeat every 15 minutes for 5 doses. Total dose 7.96 g of dibasic sodium phosphate and 22.04 g of monobasic sodium phosphate (20 tablets).

Day of procedure: 1.592 g of dibasic sodium phosphate and 4.408 g of monobasic sodium phosphate (4 tablets) with 240 mL clear liquids every 15 minutes beginning 3–5 hours before the procedure. Repeat every 15 minutes for 3 doses. Total dose 4.776 g of dibasic sodium phosphate and 13.224 g of monobasic sodium phosphate (12 tablets).

Total dosage is 12.736 g of dibasic sodium phosphate and 35.264 g of monobasic sodium phosphate with 1892 mL (2 quarts) of clear fluids. No additional enema or laxative is required.

Prescribing Limits

Pediatric Patients

Constipation

Laxatives should not be used for self-medication of constipation for ≥7 days without consulting clinician.

Magnesium Citrate
Oral

Children 2–5 years of age: For self-medication, maximum 6.25 g (usually <90 mL [5.25 g] of a 291-mg/5-mL oral solution) daily.

Children 6–11 years of age: For self-medication, maximum 12.5 g (usually <150 mL [8.75 g] of a 291-mg/5-mL oral solution) daily.

Children ≥12 years of age: For self-medication, maximum 25 g (usually <300 mL [17.5 g] of a 291-mg/5-mL oral solution) daily.

Magnesium Hydroxide
Oral

Children 2–5 years of age: For self-medication, maximum 1.2 g daily.

Children 6–11 years of age: For self-medication, maximum 2.4 g daily.

Children ≥12 years of age: For self-medication, maximum 4.8 g daily.

Magnesium Sulfate
Oral

Children 2–5 years of age: For self-medication, maximum 5 g daily.

Children 6–11 years of age: For self-medication, maximum 10 g daily.

Children ≥12 years of age: For self-medication, maximum 30 g daily.

Fixed Combination of Magnesium Hydroxide and Mineral Oil
Oral

Children 6–11 years of age: Maximum 1.8 g of magnesium hydroxide (30 mL of the fixed-combination suspension) daily.

Children ≥12 years of age: Maximum 3.6 g of magnesium hydroxide (60 mL of the fixed-combination suspension) daily.

Sodium Phosphates Enemas
Rectal

Children 2–4 years of age: For self-medication, maximum 1.75 g of dibasic sodium phosphate and 4.75 g of monobasic sodium phosphate (½ bottle [approximately 29 mL] of Fleet Pedia-Lax Enema) in 24 hours.

Children 5–11 years of age: For self-medication, maximum 3.5 g of dibasic sodium phosphate and 9.5 g of monobasic sodium phosphate (1 bottle [approximately 59 mL] of Fleet Pedia-Lax Enema) in 24 hours.

Children ≥12 years of age: For self-medication, maximum 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) in 24 hours.

Do not exceed maximum recommended dosage. Additional doses not recommended within 24 hours, even if no bowel movement occurs after a dose. (See Chronic Use or Overdosage under Cautions.)

Do not use for self-medication of occasional constipation for >3 days.

Sodium Phosphates Oral Solution
Oral

Children 5–9 years of age: For self-medication, maximum 1.35 g of dibasic sodium phosphate and 3.6 g of monobasic sodium phosphate (given as a single daily dose) in 24 hours.

Children 10–11 years of age: For self-medication, maximum 2.7 g of dibasic sodium phosphate and 7.2 g of monobasic sodium phosphate (given as a single daily dose) in 24 hours.

Children ≥12 years of age: For self-medication, maximum 8.1 g of dibasic sodium phosphate and 21.6 g of monobasic sodium phosphate (given as a single daily dose) in 24 hours.

Do not exceed maximum recommended dosage. Additional doses not recommended within 24 hours, even if no bowel movement occurs after a dose. (See Chronic Use or Overdosage under Cautions.)

Do not use for self-medication of occasional constipation for >3 days.

Bowel Cleansing
Sodium Phosphates Enemas
Rectal

Children 2–4 years of age: For self-medication, maximum 1.75 g of dibasic sodium phosphate and 4.75 g of monobasic sodium phosphate (½ bottle [approximately 29 mL] of Fleet Pedia-Lax Enema) in 24 hours.

Children 5–11 years of age: For self-medication, maximum 3.5 g of dibasic sodium phosphate and 9.5 g of monobasic sodium phosphate (1 bottle [approximately 59 mL] of Fleet Pedia-Lax Enema) in 24 hours.

Children ≥12 years of age: For self-medication, maximum 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) in 24 hours.

Adults

Constipation

Laxatives should not be used for self-medication of constipation for ≥7 days without consulting clinician.

Magnesium Citrate
Oral

For self-medication: Maximum 25 g (usually 300 mL [17.5 g] of a 291-mg/5-mL oral solution) daily.

Magnesium Hydroxide
Oral

For self-medication: Maximum 4.8 g daily.

Magnesium Sulfate
Oral

For self-medication: Maximum 30 g daily.

Fixed Combination of Magnesium Hydroxide and Mineral Oil
Oral

For self-medication: Maximum 3.6 g of magnesium hydroxide (60 mL of the fixed-combination suspension) daily.

Sodium Phosphates Enemas
Rectal

For self-medication: Maximum 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) in 24 hours.

Do not exceed maximum recommended dosage. Additional doses not recommended within 24 hours, even if no bowel movement occurs after a dose. (See Chronic Use or Overdosage under Cautions.)

Sodium Phosphates Oral Solution
Oral

For self-medication: Maximum 8.1 g of dibasic sodium phosphate and 21.6 g of monobasic sodium phosphate (given as a single daily dose) in 24 hours.

Do not exceed maximum recommended dosage. Additional doses not recommended within 24 hours, even if no bowel movement occurs after a dose. (See Chronic Use or Overdosage under Cautions.)

Bowel Cleansing
Sodium Phosphates Enemas
Rectal

For self-medication: Maximum 7 g of dibasic sodium phosphate and 19 g of monobasic sodium phosphate (1 bottle of Fleet Enema [approximately 118 mL] or Fleet Enema Extra [approximately 197 mL]) in 24 hours.

OsmoPrep Sodium Phosphates Tablets
Oral

Do not repeat sodium phosphates tablet regimen for bowel cleansing within 7 days of previous administration.

Special Populations

Hepatic Impairment

No specific dosage recommendations at this time.

Renal Impairment

Magnesium laxatives not for self-medication in patients with renal disease. (See Contraindications under Cautions.)

Sodium phosphates not for use in patients with clinically important renal function impairment. (See Contraindications and also Renal Effects under Cautions.)

Geriatric Patients

Caution advised, but no specific dosage recommendations; consider possible age-related decrease in renal and/or cardiac function and concomitant disease and drug therapy. (See Geriatric Use under Cautions.)

Cautions for Saline Laxatives

Contraindications

  • Acute abdominal pain, nausea, vomiting, or other symptoms of appendicitis or undiagnosed abdominal pain.

    Magnesium Preparations for Self-medication
  • Renal disease.

  • Magnesium-restricted diet.

  • Sudden change in bowel habits that lasts >14 days.

  • Fixed combination of magnesium hydroxide and mineral oil: Pediatric patients <6 years of age, pregnancy, bedridden patients, or difficulty swallowing.

  • Fixed combination of magnesium hydroxide and mineral oil: Concomitant use with stool softener laxatives. (See Specific Drugs under Interactions.)

    Sodium Phosphates Preparations for Self-medication
  • CHF.

  • History of kidney disease or clinically important renal function impairment.

  • Known or suspected GI obstruction, congenital or acquired megacolon, perforation, paralytic ileus, active inflammatory bowel disease, or imperforate anus.

  • Decreased intravascular volume or dehydration.

  • Uncorrected electrolyte abnormalities.

  • Known hypersensitivity to sodium phosphate salts or any ingredient in the formulation.

  • Enema: Pediatric patients <2 years of age; patients with increased absorption capacity or decreased elimination capacity.

  • Oral solution: Pediatric patients <5 years of age; use for bowel cleansing.

    Sodium Phosphates Tablets
  • Biopsy-proven acute phosphate nephropathy.

  • GI obstruction, gastric bypass or stapling surgery, bowel perforation, toxic colitis, or toxic megacolon.

  • Known hypersensitivity to sodium phosphate salts or any ingredient in the formulation.

Warnings/Precautions

Warnings

Renal Effects

Renal failure, acute phosphate nephropathy, and nephrocalcinosis reported rarely with oral sodium phosphates preparations (i.e., oral solution, OsmoPrep tablets) used for bowel cleansing; onset of kidney injury occurred from several days to several months after use. Often resulted in permanent renal function impairment and sometimes required long-term dialysis.

Risk of acute phosphate nephropathy may be increased in patients with increased age (>55 years of age), hypovolemia, increased bowel transit time (e.g., bowel obstruction), active colitis, baseline renal disease, or known or suspected electrolyte disturbances (e.g., dehydration), and in patients receiving drugs that affect renal perfusion or function (e.g., diuretics, ACE inhibitors, angiotensin II receptor antagonists, possibly NSAIAs). (See Specific Drugs under Interactions.) However, acute phosphate nephropathy also reported in patients without identifiable risk factors, although possibility of dehydration before or insufficient fluid intake after ingestion of oral sodium phosphates preparations cannot be ruled out.

Obtain baseline and postcolonoscopy laboratory measurements. (See Adequate Patient Monitoring under Cautions.)Use oral sodium phosphates preparations with caution in patients with dehydration, impaired renal function (Clcr <30 mL/minute), or history of acute phosphate nephropathy.

Because acute phosphate nephropathy also reported with OTC preparations, FDA recommends using these preparations for bowel cleansing only when a prescription for such use has been issued. In February 2011, after reviewing additional cases of acute kidney injury associated with oral sodium phosphates (some resulting in kidney transplantation, dialysis, long-term renal failure, and, rarely, death), FDA issued a proposed rule to classify sodium phosphate salts as not generally recognized as safe (GRAS) for bowel cleansing. FDA also suggested removal of the professional labeling for sodium phosphates (which discusses use of the drugs as part of a bowel cleansing regimen) from the OTC monograph for laxative drug products.

Health-care professionals should cease recommending OTC oral sodium phosphates preparations for bowel cleansing and should have removed these preparations from pharmacy shelves. Advise patients requesting an OTC oral sodium phosphates preparation for bowel cleansing to consult their clinician for an alternative bowel cleansing preparation (i.e., one available by prescription only). OTC oral sodium phosphates preparations will continue to be available for use as laxatives (i.e., for relief of constipation).

Electrolyte Abnormalities

Possible electrolyte abnormalities (e.g., hyperphosphatemia, hypernatremia, hypocalcemia, hypokalemia) with sodium phosphates preparations. May result in metabolic acidosis, renal failure, tetany, cardiac arrhythmias, prolongation of the QT interval, generalized tonic-clonic seizures, and/or loss of consciousness. (See Renal Effectsand also Seizures and also Cardiac Effects under Cautions.)

Fatalities secondary to substantial fluid shifts, severe electrolyte abnormalities, and cardiac arrhythmias reported in patients with renal insufficiency, bowel perforation, or who have misused or overused sodium phosphates preparations.

Increased risk of electrolyte disturbances in patients with dehydration, inability to take oral fluid, gastric retention, or colitis; patients taking concomitant drugs that may affect electrolyte concentrations; and geriatric patients.

Obtain baseline and postcolonoscopy laboratory measurements. (See Adequate Patient Monitoring under Cautions.)

Use sodium phosphates preparations with caution in patients with known or suspected electrolyte disturbances (e.g., dehydration). Maintain adequate hydration before, during, and after the use of such products. (See Fluid Intake under Cautions.)

Correct electrolyte abnormalities (e.g., hypernatremia, hyperphosphatemia, hypokalemia, hypocalcemia) immediately with appropriate electrolyte and fluid replacement.

Patients with electrolyte abnormalities such as hypernatremia, hyperphosphatemia, hypokalemia, or hypocalcemia should have their electrolytes corrected before treatment with OsmoPrep Tablets.

Sensitivity Reactions

Hypersensitivity Reactions

Hypersensitivity reactions, including anaphylaxis, rash, pruritus, urticaria, throat tightness, bronchospasm, dyspnea, pharyngeal edema, dysphagia, paresthesia, swelling of the lips and tongue, and facial swelling reported.

Other Warnings and Precautions

Chronic Use or Overdosage

Laxative dependence, chronic constipation, and loss of normal bowel function may occur during long-term use.

Serious, potentially life-threatening electrolyte disturbances, dehydration, and hypovolemia may occur. (See Electrolyte Abnormalities under Cautions.)

Severe dehydration, electrolyte abnormalities (e.g., hypernatremia, hyperphosphatemia, hypocalcemia), acute kidney injury, cardiac arrhythmias, and/or death reported rarely following use of OTC sodium phosphates preparations (i.e., oral solution, enema) for self-medication of occasional constipation. The majority of reported adverse events occurred in patients who received higher than recommended dosages in a 24-hour period (i.e., a single dose that was larger than recommended or >1 dose in a day) or in patients at increased risk of developing sodium phosphate-induced toxicity. Do not exceed maximum recommended dosage. (See Prescribing Limits under Dosage and Administration.)

FDA states clinicians should use caution when recommending use of OTC sodium phosphates preparations in patients >55 years of age; patients with hypovolemia, kidney disease, decreased intravascular volume, or decreased bowel transit time; and patients receiving drugs that affect renal perfusion or function (e.g., diuretics, ACE inhibitors, angiotensin II receptor antagonists, NSAIAs). (See Contraindications under Cautions and also see Interactions.)

Assess serum electrolytes and renal function in patients who may be at increased risk of developing adverse effects, including those who have retained a rectal dose for >30 minutes, who are vomiting, or who may have signs of dehydration.

Adequate Patient Monitoring

For bowel cleansing, obtain baseline and postprocedural (e.g., postcolonoscopy) laboratory measurements, including serum concentrations of electrolytes (i.e., potassium, sodium), phosphate, calcium, creatinine, and BUN in patients at increased risk for adverse events (e.g., history of renal insufficiency, history of or at greater risk of acute phosphate nephropathy, known or suspected electrolyte disorders, seizures, arrhythmias, cardiomyopathy, prolonged QT interval, recent MI, known or suspected hyperphosphatemia, hypocalcemia, hypokalemia, hypernatremia, dehydration, inability to take oral fluid, taking concomitant drugs that may affect electrolyte levels, gastric retention, colitis, elderly). Monitor GFR in smaller, frail patients.

If vomiting and/or signs of dehydration occur, obtain postcolonoscopy laboratory measurements (phosphate, calcium, potassium, sodium, creatinine, BUN).

Cardiac Effects

Prolonged QT interval and arrhythmias reported with sodium phosphates preparations; associated with severe electrolyte imbalance (e.g., hypokalemia, hypocalcemia). (See Electrolyte Abnormalities under Cautions.)

Use sodium phosphates with caution in patients with an increased risk of arrhythmias (i.e., history of cardiomyopathy, prolonged QT interval, a history of uncontrolled arrhythmias, recent MI, concomitant use of drugs known to prolong QT interval). (See Drugs Affecting QT Interval under Interactions.) Obtain baseline and postcolonoscopy laboratory measurements, including ECGs, in such patients. (See Adequate Patient Monitoring under Cautions.)

Use sodium phosphates with caution in patients with CHF, ascites, acute MI, unstable angina, and recent cardiac surgery (including CABG). Some manufacturers state that sodium phosphates preparations are contraindicated in patients with CHF or ascites.

CHF has occurred with indiscriminate use of sodium-containing saline laxatives.

Seizures

Rarely, generalized tonic-clonic seizures and/or loss of consciousness reported with sodium phosphates preparations; associated with electrolyte abnormalities and low serum osmolality. (See Electrolyte Abnormalities under Cautions.) Resolved with correction of fluid and electrolyte abnormalities.

Use sodium phosphates with caution in patients with history of seizures or at higher risk of seizures (e.g., known or suspected hyponatremia, withdrawing from alcohol or benzodiazepines, concomitant use of drugs that lower the seizure threshold). (See Specific Drugs under Interactions.) Obtain baseline and postcolonoscopy laboratory measurements in such patients. (See Adequate Patient Monitoring under Cautions.)

GI Effects

Use oral sodium phosphates preparations with caution in patients with gastric retention, pseudo-obstruction of the bowel, severe chronic constipation, delayed bowel emptying, severe active ulcerative colitis, colostomy or ileostomy, or hypomotility syndrome. Obtain baseline and postcolonoscopy laboratory measurements in such patients. (See Adequate Patient Monitoring and also Contraindications under Cautions.)

Sodium phosphates preparations may induce colonic mucosal aphthous ulceration; consider in patients with known or suspected inflammatory bowel disease.

Possible increased sodium phosphate absorption during an acute exacerbation of chronic inflammatory bowel disease; use with caution. Some manufacturers state that sodium phosphates preparations are contraindicated in patients with active inflammatory bowel disease.

Use of Fixed Combinations

When magnesium hydroxide is used in fixed combination with mineral oil, consider the cautions, precautions, and contraindications associated with mineral oil.

When magnesium citrate or sodium phosphates is used in regimens with bisacodyl, consider the cautions, precautions, and contraindications associated with bisacodyl.

Fluid Intake

Inadequate fluid intake may lead to excessive fluid loss, hypovolemia, and dehydration; may be associated with acute renal failure. (See Renal Effects under Cautions.)

Obtain baseline and postcolonoscopy laboratory measurements in dehydrated patients or those unable to take oral fluids. (See Adequate Patient Monitoring under Cautions.)

Dehydration from purgation exacerbated by inadequate oral fluid intake, nausea, vomiting, and/or use of diuretics or other drugs. (See Specific Drugs under Interactions.)

Patients must have adequate fluid intake before, during, and after bowel cleansing regimens.

Assess hydration status in patients at risk for dehydration prior to use of purgatives.

Swallowing Difficulties

Undigested or partially digested tablets of sodium phosphates or other drugs may be seen in stool or during colonoscopy in patients with swallowing difficulties, anatomic narrowing of the esophagus, or stricture.

Dietary Considerations

Magnesium laxatives not for self-medication in patients on a magnesium-restricted diet.

Carbon dioxide-releasing suppositories not for self-medication in patients on a low-salt diet.

Use sodium phosphates preparations with caution in patients on a low-salt diet.

Electrolytic Content

CEO-TWO suppositories contain 164 mg (7.13 mEq) of sodium per suppository.

Each level teaspoonful of magnesium sulfate crystals contains approximately 5 g of magnesium sulfate and 495 mg (40.7 mEq) of magnesium.

Magnesium citrate oral solution contains 0.33 mg of sodium and 3.85–4.71 mEq of magnesium per 5 mL.

Magnesium hydroxide contains about 34.3 mEq of magnesium per g of the drug; milk of magnesia (regular strength [400 mg/5 mL]) contains approximately 2.4–2.9 mEq of magnesium per g or 13.66 mEq of magnesium per 5 mL.

Fleet Enema and Fleet Pedia-Lax Enema contain 37 mg (1.61 mEq) of sodium per mL and 4.15 mEq of phosphate per mL (total sodium content: 4.4 g in 118 mL and 2.2 g in 59 mL, respectively). Fleet Enema Extra contains 22 mg of sodium per mL (total sodium content: 4.4 g in 197 mL).

Sodium Phosphate Oral Solutions contains 556 mg (24.1 mEq) of sodium per 5 mL.

OsmoPrep tablets contain 0.398 g of dibasic sodium phosphate and 1.102 g of monobasic sodium phosphate per tablet.

Specific Populations

Pregnancy

Magnesium sulfate: Category B.

Sodium phosphates: Category C.

Lactation

Magnesium sulfate may be distributed into milk in small amounts.

The AAP classifies magnesium sulfate as compatible with breast-feeding.

Pediatric Use

Avoid use of laxatives in infants and children; counsel parents on acceptable variations in frequency of bowel movements.

Magnesium citrate preparations for bowel cleansing: Use in children <12 years of age only as directed by clinician.

Magnesium citrate for laxative use: Use in children <2 years of age only as directed by clinician.

Magnesium hydroxide: Not for self-medication in children <2 years of age.

Fixed combination of magnesium hydroxide and mineral oil: Not for self-medication in children <6 years of age.

Oral magnesium sulfate preparations: Not for self-medication in children <6 years of age.

Oral sodium phosphates preparations for bowel cleansing: Safety and efficacy not established in children <18 years of age; avoid use in such children.

Oral sodium phosphates preparations for laxative use: Not for self-medication in children <5 years of age. Clinicians should be cautious in recommending use of these preparations in children ≤5 years of age.

Rectal sodium phosphates enemas: Safety and efficacy not established in children <2 years of age; avoid use in such children.

Carbon-dioxide releasing suppositories: Use in children <12 years of age only as directed by clinician.

Geriatric Use

Sodium phosphates preparations: Safety and efficacy in those ≥65 years of age similar to younger adults; manufacturers state that sodium phosphates should be used with caution in such patients due to greater frequency of decreased renal and/or cardiac function and of concomitant disease and drug therapy observed in the elderly. (See Special Populations under Pharmacokinetics.) FDA recommends caution when using oral sodium phosphates preparations as bowel cleansing regimens in patients >55 years of age due to increased risk of acute phosphate nephropathy. (See Renal Effects under Cautions.)

Severe and potentially fatal cases of electrolyte disorders possible; consider risk/benefit. Consider baseline and postcolonoscopy laboratory measurements. (See Electrolyte Abnormalities and also see Adequate Patient Monitoring under Cautions.)

Hepatic Impairment

Sodium phosphates tablets: Not studied in patients with hepatic impairment.

Restrict use of sodium-containing saline laxatives in patients with cirrhosis.

Avoid use of sodium phosphates preparations in patients with ascites.

Renal Impairment

Sodium phosphates preparations: Use with caution in renal impairment. Manufacturer of OsmoPrep states that this preparation should be used with extreme caution in patients with severe renal impairment (Clcr <30 mL/minute); however, other manufacturers state use is contraindicated in patients with clinically important renal impairment. Obtain baseline and postcolonoscopy laboratory measurements. (See Renal Effects and also see Adequate Patient Monitoring under Cautions.)

Death secondary to substantial fluid shifts, severe electrolyte abnormalities, and cardiac arrhythmias reported in patients with renal impairment.

Magnesium laxatives not for self-medication in patients with renal disease.

Possible accumulation of magnesium, potassium, or sodium in patients with renal disease; use laxative products containing >50 mEq of magnesium, 25 mEq of potassium, or 1 mEq of sodium per dose only under supervision of a clinician and monitor electrolytes. (See Electrolytic Content under Cautions.)

Common Adverse Effects

Sodium phosphates preparations: Dehydration, abdominal pain, bloating, nausea, vomiting, headache, dizziness, hyperphosphatemia, hypocalcemia, hypokalemia.

Carbon dioxide-releasing suppositories: Rectal discomfort, burning sensation.

Magnesium citrate: Abdominal discomfort, faintness, rectal burning, mild cramps.

Interactions for Saline Laxatives

GI Drug Absorption

By increasing intestinal motility, can potentially decrease transit time of concomitantly administered oral drugs and decrease their absorption.

Administer magnesium sulfate ≥2 hours before or after other drugs.

Drugs Affecting QT Interval

Risk of prolonged QT interval and potentially serious or life-threatening arrhythmias. Use sodium phosphates preparations with caution in combination with drugs that prolong the QT interval. (See Cardiac Effects under Cautions.)

Drugs Affecting Renal Perfusion or Function

Increased risk of acute phosphate nephropathy (nephrocalcinosis) when used concomitantly with sodium phosphates preparations. (See Renal Effects under Cautions.)

Drugs Affecting Electrolyte Levels

Increased risk of electrolyte abnormalities (e.g., hypernatremia, hyperphosphatemia, hypokalemia, hypocalcemia) when used concomitantly with sodium phosphates preparations. Avoid concomitant use with other laxatives containing sodium phosphate.

Drugs Affecting Seizure Threshold

Possible increased risk of seizure when used concomitantly with sodium phosphates preparations.

Specific Drugs

Drug

Interaction

Comments

Alcohol

Possible increased risk of seizures for patients withdrawing from alcohol

Use caution when administering sodium phosphates preparations concomitantly during alcohol withdrawal

ACE inhibitors

Increased risk of dehydration, hypovolemia, or acute phosphate nephropathy

Use concomitantly with caution

Angiotensin II receptor antagonists

Increased risk of dehydration, hypovolemia, and acute phosphate nephropathy

Use concomitantly with caution

Antibiotics

Possible delayed or decreased absorption from the GI tract

Efficacy may be reduced or absent

Anticonvulsants

Possible delayed or decreased absorption from the GI tract

Efficacy may be reduced or absent

Antidiabetic agents

Possible delayed or decreased absorption from the GI tract

Efficacy may be reduced or absent

Benzodiazepines

Possible increased risk of seizures for patients withdrawing from benzodiazepines

Use caution when administering sodium phosphates preparations concomitantly during benzodiazepine withdrawal

Diuretics

Increased risk of dehydration and acute phosphate nephropathy

Correct electrolyte balances before treating with sodium phosphates preparations

Administer concomitantly with caution

Laxatives or purgative agents

Possible additive effects

Do not use sodium phosphates preparations with additional laxatives or purgative agents

Lithium

Increased risk of dehydration, hypovolemia, and electrolyte abnormalities

NSAIAs

Increased risk of dehydration, hypovolemia, and acute phosphate nephropathy

Use concomitantly with caution

Oral contraceptives

Delayed or decreased absorption from the GI tract possible

Efficacy may be reduced or absent

Stool softener laxatives (e.g., docusate)

Increased rate of mineral oil absorption

Do not use fixed combination containing magnesium hydroxide and mineral oil concurrently with docusate

Tricyclic antidepressants (TCAs)

Possible increased risk of seizures

Use caution when administered concomitantly with sodium phosphates preparations

Saline Laxatives Pharmacokinetics

Absorption

Bioavailability

Oral magnesium-containing laxatives: 15–30% may be absorbed.

Oral phosphate laxatives: Extent of phosphate and sodium absorption unknown.

Rectal phosphate enemas: Extent of phosphate absorption unknown; reportedly 1–20% of sodium and phosphate absorbed.

Onset

Bowel movement usually occurs within 0.5–6 hours following oral administration of magnesium- or phosphate-containing laxatives.

Bowel movement usually occurs within 5–30 minutes following rectal administration of carbon dioxide-releasing suppositories.

Bowel movement usually occurs within 1–5 minutes following administration of phosphate-containing rectal enemas.

Duration

Purgative effects of sodium phosphates tablets (OsmoPrep) persist for 1–3 hours.

Distribution

Extent

Magnesium is distributed into saliva and milk in small amounts.

Elimination

Elimination Route

Magnesium and phosphate are excreted principally by the kidneys.

Special Populations

Pharmacokinetics of sodium phosphates tablets not evaluated in patients with renal impairment; however, patients with renal disease may have difficulty excreting a large phosphate load.

In geriatric patients >70 years of age, plasma half-life of oral sodium phosphates tablets increased twofold.

Stability

Storage

Oral

Solutions

Magnesium citrate: 2–30°C; protect from excessive heat and freezing. Discard within 24 hours of opening.

Sodium phosphates: May refrigerate; do not freeze.

Suspensions

Magnesium hydroxide: Room temperature; avoid freezing. Keep tightly closed.

Fixed-combination magnesium hydroxide and mineral oil: Room temperature; avoid freezing. Keep tightly closed.

Tablets

Sodium phosphates: 25°C (may be exposed to 15–30°C).

Tablets, Chewable

Magnesium hydroxide: Room temperature.

Rectal

Suppositories

CEO-TWO suppositories: 20–25°C (do not exceed 30°C). Do not refrigerate.

Actions

  • Precise mechanism of action not known. Laxative action may result from the hyperosmotic effect of poorly absorbed magnesium or phosphate ions within the small intestine causing the retention of water, indirectly stimulating stretch receptors and increasing peristalsis. However, isosmolarity is present at the ligament of Treitz following ingestion of hyperosmolar meals.

  • Laxative action of magnesium also may be the result of cholecystokinin release or decreased transit time.

  • Effectiveness of phosphate enemas may reflect the volume of liquid introduced rectally.

  • Orally administered saline laxatives act mainly on the small intestine. Saline suppositories or enemas generally promote evacuation of the colon only.

  • Insufficient sodium biphosphate in rectal suppositories to exert an effect as a saline laxative; facilitates the chemical reaction that produces carbon dioxide (CO2). Rectal suppositories containing potassium bitartrate and sodium bicarbonate also produce CO2; promotes laxation by exerting pressure in the rectum as CO2 expands. Does not alter normal peristaltic reflex.

Advice to Patients

  • Advise patient to open and read directions for bowel cleansing preparations at least 2 days in advance of examination. Importance of following complete regimen for bowel cleansing preparations.

  • Advise patients of the importance of taking the recommended fluid regimen including hydrating before, during, and after bowel cleansing regimens. Advise patients of early symptoms of dehydration (e.g., feeling thirsty, dizziness, urinating less often than normal, vomiting). In patients receiving oral sodium phosphates preparations, advise of symptoms of acute phosphate nephropathy (e.g., malaise; lethargy; drowsiness; decreased amount of urine; swelling of the ankles, feet, and legs).

  • Importance of drinking 240 mL of liquid with each dose of laxative.

  • Importance of not using additional enemas or laxatives with sodium phosphates preparations; importance of taking only recommended dosage.

  • Importance of not repeating oral sodium phosphates bowel cleansing regimen within 7 days of previous use.

  • When using sodium phosphates preparations as laxatives, importance of not taking more than one dose in a 24-hour period.

  • Importance of informing clinicians before use if abdominal pain, nausea, or vomiting is present or if a sudden change in bowel habits occurs that persists >14 days.

  • Importance of discontinuing use and informing clinician if a bowel movement does not occur or rectal bleeding occurs after use; importance of contacting clinician if no return of liquid after using enema solution. Importance of discontinuing therapy and immediately seeking medical attention if symptoms of kidney injury (e.g., drowsiness; sluggishness; decreased urine; swelling of the ankles, feet, or legs) occur.

  • Advise patients on low-salt diets to consult clinician before using sodium phosphates laxatives.

  • Importance of not using laxatives for >7 days unless directed by a clinician.

  • Importance of administering proper enema solution for patient age.

  • Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, and dietary restrictions, as well as any concomitant illnesses, including seizures, kidney disease, heart disease, or GI disorders.

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

  • Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Magnesium Citrate (Citrate of Magnesia)

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Bulk

Powder

Oral

Solution*

291 mg/5 mL

Magnesium Citrate Oral Solution

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Magnesium Hydroxide

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Bulk

Powder

Oral

Suspension*

400 mg/5 mL*

Milk of Magnesia

Phillips’ Milk of Magnesia

Bayer

800 mg/5 mL

Little Phillips’ Milk of Magnesia

Bayer

Phillips’ Concentrated Milk of Magnesia

Bayer

1.2 g/5 mL*

Milk of Magnesia Concentrate

Tablets, chewable

311 mg

Phillips’ Chewable Tablets

Bayer

400 mg

Fleet Pedia-Lax Chewable Tablets

Fleet

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Magnesium Hydroxide Combinations (combination)

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Suspension

300 mg (magnesium hydroxide)/5 mL with Mineral Oil 1.25 mL/5 mL*

Phillips’ M-O(combination)

Bayer

4 mL (milk of magnesia)/5 mL with Mineral Oil 1 mL/5 mL*

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Magnesium Sulfate (Epsom Salt)

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Bulk

Crystals*

Bulk

Powder*

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Sodium Phosphate, Dibasic

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Bulk

Powder*

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Sodium Phosphate, Monobasic

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Bulk

Powder*

Carbon Dioxide-releasing Suppositories

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Rectal

Suppository

Potassium Bitartrate 0.9 g and Sodium Bicarbonate 0.6 g

Ceo-Two

Beutlich

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Sodium Phosphates

Routes

Dosage Forms

Strengths

Brand Names

Manufacturer

Oral

Solution

Dibasic Sodium Phosphate 900 mg/5 mL with Monobasic Sodium Phosphate 2.4 g/5 mL*

Sodium Phosphate Oral Saline Laxative

Tablet

Dibasic Sodium Phosphate (anhydrous) 0.398 g with Monobasic Sodium Phosphate (monohydrate) 1.102 g

OsmoPrep

Salix

Rectal

Solution

Dibasic Sodium Phosphate 36 mg/mL with Monobasic Sodium Phosphate 96 mg/mL

Fleet Enema Extra

Fleet

Dibasic Sodium Phosphate 59 mg/mL with Monobasic Sodium Phosphate 161 mg/mL

Fleet Enema

Fleet

Fleet Pedia-Lax Enema

Fleet

AHFS DI Essentials™. © Copyright 2021, Selected Revisions October 1, 2014. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

† Use is not currently included in the labeling approved by the US Food and Drug Administration.

Show article references