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, Fleet Prep Kit, LoSo Prep Kit, OsmoPrep, Phillips' Milk of Magnesia, Phillips' M-O, Tridrate Kit, Visicol

Introduction

Laxatives containing magnesium cations or phosphate anions.^a

Uses for Saline Laxatives

Constipation

Used to relieve occasional constipation.^{214 215 216 217 218 219 220 224 225 227 231 b}

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

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

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.^b

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.^b Alternatively, administer phosphate-containing saline enemas rectally after manual disimpaction to promote evacuation of fecal impactions.^b

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.^{212 213 219 220 221 222 223 227 232 b} Oral therapy often is supplemented with rectal evacuants.^{221 222 223 232 b}

FDA recommends using OTC oral sodium phosphates preparations for bowel cleansing only when a prescription for such use has been issued by a clinician.^{239 240} (See Renal Effects under Cautions.)

Poisonings

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

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).^{212 213 220 221 222 223 229 230 b} Use IV hydration in a hospital setting for fragile patients with inadequate home support or who are unable to drink an appropriate fluid volume.^{239 b} (See Fluid Intake under Cautions.)

Administration

Administer magnesium-containing saline laxatives orally as chewable tablets, suspensions, or solutions.^{215 216 217 218 222 223 224 225 232}

Administer phosphate-containing laxatives orally as solutions or tablets and rectally as enemas.^{212 213 219 220 221 227 228 229 230} Do not administer commercially available phosphate-containing rectal enema solutions orally.^{219 227 228}

Administer carbon dioxide-releasing suppositories (e.g., CEO-TWO) rectally.²¹⁴

Select rectal phosphate-containing laxatives carefully to ensure appropriate volume for age to minimize risk of overdosage.^{219 227 228}

Administer laxatives as infrequently as possible at the lowest effect dosage level.^b Do not use for >7 days unless directed by prescriber.^{215 216 b}

Administer laxatives with sufficient fluids (i.e., 240 mL) to prevent dehydration from repeated administration.^{215 216 217 218 224 225 233 b} (See Fluid Intake under Cautions.)

Oral Administration

Administer orally as magnesium-containing chewable tablets, suspensions, or solutions or as phosphate-containing solutions or tablets.^{212 213 215 216 217 218 219 220 221 222 223 224 225 227 228 229 230 232 233 235}

Do not administer fixed combination of magnesium hydroxide and mineral oil with meals; typically administered at bedtime.²¹⁸

Shake suspensions well before use.^{215 216 218}

May refrigerate oral sodium phosphates solutions to improve taste;²²⁰ may drink magnesium citrate chilled.²²²

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.^{225 b}

Reconstitution (LoSo Prep Kit)

Prepare magnesium citrate oral solution by dissolving contents of 1 packet (18 g of magnesium citrate) in 240 mL of cold water.²³² First, add approximately one-half of the contents of the packet to a large (capacity of ≥480 mL) glass containing 240 mL of cold water, gently stir the mixture until effervescence (fizzing) stops, then add the remaining contents of the packet to the mixture and again stir gently until effervescence stops.²³²

Reconstitution (Tridrate Dry Kit)

Prepare magnesium citrate oral solution by adding the contents of 1 packet (19 g of magnesium citrate) to 240 mL of room-temperature water; stir the mixture for 30 seconds until complete dissolution occurs.²²⁶ Patient should wait ≥20 minutes before ingesting the mixture, occasionally stirring it in the interim.²²⁶ May prepare the solution up to 12 hours prior to ingestion and chill to improve taste.²²⁶

Dilution (Fleet Prep Kits)

Dilute sodium phosphates oral solution (Fleet Phospho-soda) prior to administration.^{220 229 230} Mix 45 mL of the solution with 360 mL of cold clear liquid (ginger ale, apple juice, Sprite, or 7-Up may help improve taste).^{220 229 230}

Rectal Administration

Administer rectally as phosphate-containing enemas or carbon dioxide-releasing suppositories.^{214 219 227 228}

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;^{214 231 234} do not use mineral oil or petroleum jelly to lubricate.^{214 231 234}

Insert suppository high into the rectum past the largest diameter of the suppository;²¹⁴ retain for as long as possible (usually 5–30 minutes) before defecating.^{214 231 b}

Enemas

Administer sodium phosphates enema at room temperature.²¹⁹

Remove protective shield (if present) from tip of enema.^{219 228}

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.^{219 228 b}

With steady pressure, insert enema nozzle into rectum, with nozzle pointed toward the navel.^{219 b} To ease insertion, have patient bear down as if having a bowel movement.²¹⁹ Squeeze container until nearly all the liquid is expelled.^{219 228 b} Use caution to avoid bowel perforation.²¹⁹ If resistance is encountered during insertion or administration, discontinue procedure to avoid perforation or rectal abrasion.²¹⁹

Retain until definite lower abdominal cramping felt.^b Complete evacuation of the left colon usually occurs within 1–5 minutes.²¹⁹

Disposable enemas are for single-use only.²¹⁹

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.²²⁷ 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.²²⁷ Replace the cap and administer the enema as directed.²²⁷

Dosage

Most studies suggest that the minimum effective oral laxative dose of magnesium is 80 mEq.^a (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.²²⁵

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;²²⁷ 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.²¹⁹

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.^{214 215 216 217 218 219 220 221 223 225 232} (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 solution²²⁴ ) as a single daily dose or in divided doses.²³⁴

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 solution²²⁴ ) as a single daily dose or in divided doses.²³⁴

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 solution²²⁴ ) as a single daily dose or in divided doses.²³⁴

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.^{217 233 234 235}

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.^{215 216 217 218 233 234 235}

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.^{215 216 217 218 233 234}

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.²³⁴

Children 6–11 years of age: For self-medication, 5–10 g daily given as a single dose or in divided doses.^{225 234}

Children ≥12 years of age: For self-medication, 10–30 g daily given as a single dose or in divided doses.^{225 234}

Fixed Combination of Magnesium Hydroxide and Mineral Oil

Oral

Do not use manufacturer's provided dosage cup for Phillips' M-O for children.²¹⁸

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.²¹⁸

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.²¹⁸

Sodium Phosphates Enemas

Rectal

Do not administer adult-size Fleet enemas to children <12 years of age.²¹⁹ Do not administer a full 59-mL Fleet Pedia-Lax Enema to children <5 years of age.^{219 227}

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.²²⁷ To obtain correct dose, remove 30 mL liquid from Fleet Pedia-Lax Enema prior to administration.²²⁷

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.²²⁷

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.^{219 228}

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.^{214 231 234}

Bowel Cleansing

Consult manufacturers' instructions 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.^{222 223 226 232}

Fleet Sodium Phosphates Enemas

Rectal

Do not administer adult-size Fleet enemas to children <12 years of age.²¹⁹ Do not administer a full 59-mL Fleet Pedia-Lax Enema to children <5 years of age.^{219 227}

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.²²⁷ To obtain correct dose, remove 30 mL liquid from Fleet Pedia-Lax Enema prior to administration.²²⁷

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.²²⁷

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.^{219 228}

Liquid LoSo Prep Kit

Oral and Rectal

The regimen begins with liquid meals at prescribed times, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²²³

Children ≥12 years of age: In the usual regimen, 300 mL of magnesium citrate solution (17.45 g of magnesium citrate) is administered orally at 5:30 p.m. the day before the procedure, followed by 20 mg of bisacodyl orally at 7:30 p.m. the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository inserted at least 2 hours before the procedure.²²³

LoSo Prep Kit

Oral and Rectal

The regimen begins with liquid meals at prescribed times, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²³²

Children ≥12 years of age: In the usual regimen, 18 g of magnesium citrate (1 packet dissolved in 240 mL water) is administered orally at 5:30 p.m. the day before the procedure, followed by 20 mg of bisacodyl orally at 7:30 p.m. the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository inserted at least 2 hours before the procedure.²³²

Tridrate Kit

Oral and Rectal

The regimen begins with a meal (i.e., clear liquids, chicken or turkey white meat sandwich without condiments, skim milk) at a prescribed time, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²²²

Children >12 years of age: In the usual regimen, 300 mL of magnesium citrate solution is administered orally at 8 p.m. the day before the procedure, followed by 15 mg of bisacodyl orally at 10 p.m. the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository at 7 a.m. the morning of the procedure.²²²

Tridrate Dry Kit

Oral and Rectal

The regimen begins with liquid meals at prescribed times, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²²⁶

Children >12 years of age: In the usual regimen, 19 g of magnesium citrate (1 packet dissolved in 240 mL water) is administered orally in 2 divided doses at 6 p.m. and 6:15 p.m. the day before the procedure, followed by 15 mg of bisacodyl orally at bedtime (between 9 p.m. and midnight) the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository at 7 a.m. the morning of (at least 2 hours before) the procedure.²²⁶

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.^{214 215 216 217 218 219 220 221 223 225 232 b} (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 solution²²⁴ ) as a single daily dose or in divided doses.²³⁴

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.^{215 216 217 218 233 234}

Magnesium Sulfate

Oral

For self-medication: 10–30 g daily given as a single dose or in divided doses.^{225 234}

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.²¹⁸

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.^{219 228}

Carbon Dioxide-releasing Suppositories

Rectal

1 suppository (0.9 g potassium bitartrate and 0.6 g sodium bicarbonate) given as a single daily dose.^{214 231 234}

Bowel Cleansing

Fleet Prep Kits

Oral and Rectal

Available in 2 kit combinations containing sodium phosphates oral solution, bisacodyl tablets, and either a bisacodyl suppository (Fleet Prep Kit 1) or a bisacodyl enema (Fleet Prep Kit 3).²²¹

Each kit can be administered in regimens beginning 18 or 24 hours before the procedure; in most cases, the 24-hour regimen is followed.²²¹

Each regimen begins with a light meal at a prescribed time, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of either a bisacodyl suppository or bisacodyl enema 1 hour before leaving for the procedure.²²¹

Kit 1, 24-hour regimen: The day before the procedure, 45 mL of sodium phosphates oral solution (Fleet Phospho-soda) is mixed with 360 mL of cold clear liquid and administered orally at 4 p.m. with ≥360 mL of clear liquid, followed by 20 mg (or alternative dose per clinician) of bisacodyl orally at 9 p.m. the day before the procedure, and then by a 10-mg bisacodyl rectal suppository administered 1 hour before leaving for the procedure.^{221 229}

Kit 3, 24-hour regimen: The day before the procedure, 45 mL of sodium phosphates oral solution (Fleet Phospho-soda) is mixed with 360 mL of cold clear liquid and administered orally at 4 p.m. with ≥240 mL of clear liquid, followed by 20 mg (or alternative dose per clinician) of bisacodyl orally at 9 p.m. the day before the procedure, and then by a 10-mg (30-mL) bisacodyl enema administered 1 hour before leaving for the procedure.^{221 230}

Drink as much additional liquid as possible; drink additional liquids after procedure to prevent dehydration.^{221 229 230}

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.^{219 228}

Liquid LoSo Prep Kit

Oral and Rectal

The regimen begins with liquid meals at prescribed times, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²²³

In the usual regimen, 300 mL of magnesium citrate solution (17.45 g of magnesium citrate) is administered orally at 5:30 p.m. the day before the procedure, followed by 20 mg of bisacodyl orally at 7:30 p.m. the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository inserted at least 2 hours before the procedure.²²³

LoSo Prep Kit

Oral and Rectal

The regimen begins with liquid meals at prescribed times, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²³²

In the usual regimen, 18 g of magnesium citrate (1 packet dissolved in 240 mL water) is administered orally at 5:30 p.m. the day before the procedure, followed by 20 mg of bisacodyl orally at 7:30 p.m. the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository inserted at least 2 hours before the procedure.²³²

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.²¹³ Total dose 7.96 g of dibasic sodium phosphate and 22.04 g of monobasic sodium phosphate (20 tablets).²¹³

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.²¹³ Repeat every 15 minutes for 3 doses.²¹³ Total dose 4.776 g of dibasic sodium phosphate and 13.224 g of monobasic sodium phosphate (12 tablets).²¹³

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.²¹³ No additional enema or laxative is required.²¹³

Tridrate Kit

Oral and Rectal

The regimen begins with a meal (i.e., clear liquids, chicken or turkey white meat sandwich without condiments, skim milk) at a prescribed time, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²²²

In the usual regimen, 300 mL of magnesium citrate solution is administered orally at 8 p.m. the day before the procedure, followed by 15 mg of bisacodyl orally at 10 p.m. the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository at 7 a.m. the morning of the procedure.²²²

Tridrate Dry Kit

Oral and Rectal

The regimen begins with liquid meals at prescribed times, followed by scheduled clear liquid intake at various times and scheduled administration of oral laxatives, and concludes with rectal administration of a bisacodyl suppository.²²⁶

In the usual regimen, 19 g of magnesium citrate (1 packet dissolved in 240 mL water) is administered orally in 2 divided doses at 6 p.m. and 6:15 p.m. the day before the procedure, followed by 15 mg of bisacodyl orally at bedtime (between 9 p.m. and midnight) the day before the procedure, and concludes with a 10-mg bisacodyl rectal suppository at 7 a.m. the morning of (at least 2 hours before) the procedure.²²⁶

Visicol Sodium Phosphates Tablets

Oral

Evening before procedure: 1.194 g of dibasic sodium phosphate and 3.306 g of monobasic sodium phosphate (3 tablets) with 240 mL clear liquids; repeat every 15 minutes for 7 doses (last dose is 2 tablets).²¹² Total dose 7.96 g of dibasic sodium phosphate and 22.04 g of monobasic sodium phosphate (20 tablets).²¹²

Day of procedure: 1.194 g of dibasic sodium phosphate and 3.306 g of monobasic sodium phosphate (3 tablets) with 240 mL clear liquids every 15 minutes beginning 3–5 hours before the procedure.²¹² Repeat every 15 minutes for 7 doses (last dose is 2 tablets).²¹² Total dose 7.96 g of dibasic sodium phosphate and 22.04 g of monobasic sodium phosphate (20 tablets).²¹²

Total dosage is 15.92 g of dibasic sodium phosphate and 44.08 g of monobasic sodium phosphate (40 tablets) with 3405 mL (3.6 quarts) of clear fluids.²¹² No additional enema or laxative is required.²¹²

Prescribing Limits

Pediatric Patients

Constipation

Laxatives should not be used for self-medication of constipation for ≥7 days without consulting clinician.^{214 215 216 217 218 219 220 221 223 225 231 232 b}

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.^{224 234}

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.^{224 234}

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.^{224 234}

Magnesium Hydroxide

Oral

Children 2–5 years of age: For self-medication, maximum 1.2 g daily.^{217 233 234 235}

Children 6–11 years of age: For self-medication, maximum 2.4 g daily.^{215 216 217 218 233 234 235}

Children ≥12 years of age: For self-medication, maximum 4.8 g daily.^{215 216 217 218 233 234}

Magnesium Sulfate

Oral

Children 2–5 years of age: For self-medication, maximum 5 g daily.²³⁴

Children 6–11 years of age: For self-medication, maximum 10 g daily.^{225 234}

Children ≥12 years of age: For self-medication, maximum 30 g daily.^{225 234}

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.²¹⁸

Children ≥12 years of age: Maximum 3.6 g of magnesium hydroxide (60 mL of the fixed-combination suspension) daily.²¹⁸

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.²²⁷

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.²²⁷

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.^{219 228}

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.²²⁷

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.²²⁷

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.²²⁸

Adults

Constipation

Laxatives should not be used for self-medication of constipation for ≥7 days without consulting clinician.^{214 215 216 217 218 219 220 221 223 225 231 232 b}

Magnesium Citrate

Oral

For self-medication: Maximum 25 g (usually 300 mL [17.5 g] of a 291-mg/5-mL oral solution) daily.^{224 234}

Magnesium Hydroxide

Oral

For self-medication: Maximum 4.8 g daily.^{215 216 217 218 233 234}

Magnesium Sulfate

Oral

For self-medication: Maximum 30 g daily.^{225 234}

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.²¹⁸

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.^{219 228}

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.^{219 228}

OsmoPrep Sodium Phosphates Tablets

Oral

Do not repeat sodium phosphates tablet regimen for bowel cleansing within 7 days of previous administration.²¹³

Visicol Sodium Phosphates Tablets

Oral

Do not repeat sodium phosphates tablet regimen for bowel cleansing within 7 days of previous administration.²¹²

Special Populations

Hepatic Impairment

No specific dosage recommendations at this time.^{212 213}

Renal Impairment

Magnesium laxatives not for self-medication in patients with renal disease.^{215 216 217 218 222 223 225 232} (See Contraindications under Cautions.)

Sodium phosphates not for use in patients with clinically important renal function impairment.^{219 220} (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.^{212 213 221} (See Geriatric Use under Cautions.)

Cautions for Saline Laxatives

Contraindications

• Acute abdominal pain, nausea, vomiting, or other symptoms of appendicitis or undiagnosed abdominal pain.^{214 215 216 217 218 219 220 222 223 225 b}

• Sodium Phosphates Preparations

• Known hypersensitivity to sodium phosphate salts or any ingredient in the formulation.^{212 213 220}

• Biopsy-proven acute phosphate nephropathy²¹² or clinically important renal function impairment.^{219 220 221 227 228 229 230}

• CHF.^{219 220 221 227 228 229 230}

• Ascites.^{219 220 221 227 228}

• Known or suspected GI obstruction,^{219 220 221 227 228} congenital or acquired megacolon,^{219 220 221 227 228} perforation,^{220 221} ileus,^{220 221} or active inflammatory bowel disease.^{220 221}

• Oral solution for bowel cleansing: Pediatric patients <18 years of age.^{220 221 239}

• Rectal solutions: Pediatric patients <2 years of age.²¹⁹

• Magnesium Preparations for Self-medication

• Renal disease.^{215 216 217 218 223 224 225}

• Magnesium-restricted diet.^{215 216 217 218 224 225}

• Sudden change in bowel habits that lasts >14 days.^{215 216 217 218 224 225 b}

• Fixed combination of magnesium hydroxide and mineral oil: Pediatric patients <6 years of age, pregnancy, bedridden patients, or difficulty swallowing.²¹⁸

• Fixed combination of magnesium hydroxide and mineral oil: Concomitant use with stool softener laxatives.²¹⁸ (See Specific Drugs under Interactions.)

Warnings/Precautions

Warnings

Chronic Use or Overdosage

Laxative dependence, chronic constipation, and loss of normal bowel function may occur during long-term use.^{222 223 232 b}

Serious, potentially life-threatening electrolyte disturbances, dehydration, and hypovolemia may occur.^{212 219 220 221 b} (See Electrolyte Abnormalities under Cautions.)

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,^{212 213} dehydration,^{220 221} inability to take oral fluid,^{220 221} taking concomitant drugs that may affect electrolyte levels,^{212 213 219 220} gastric retention,^{212 213 220 221} colitis,^{220 221} elderly).^{220 221} Monitor GFR in smaller, frail patients.²³⁹

If vomiting and/or signs of dehydration occur, obtain postcolonoscopy laboratory measurements (phosphate, calcium, potassium, sodium, creatinine, BUN).^{212 213}

Electrolyte Abnormalities

Possible electrolyte abnormalities (e.g., hyperphosphatemia, hypernatremia, hypocalcemia, hypokalemia) with sodium phosphates preparations.^{212 213 219 220 227 228 b} May result in metabolic acidosis, renal failure, tetany, cardiac arrhythmias, prolongation of the QT interval, generalized tonic-clonic seizures, and/or loss of consciousness.^{212 213} (See Renal Effects and 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.^{212 213 219}

Increased risk of electrolyte disturbances in patients with dehydration,^{220 221} inability to take oral fluid,^{220 221} gastric retention,^{212 213 220 221} or colitis;^{220 221} patients taking concomitant drugs that may affect electrolyte concentrations;^{212 213 219 220} and geriatric patients.^{220 221}

Use sodium phosphates preparations with caution in patients with known or suspected electrolyte disturbances (e.g., dehydration).^{212 213 227 228} Maintain adequate hydration before, during, and after the use of such products.^{212 213 219} (See Fluid Intake under Cautions.)

Correct electrolyte abnormalities (e.g., hypernatremia, hyperphosphatemia, hypokalemia, hypocalcemia) immediately with appropriate electrolyte and fluid replacement.^{212 219 220 221}

Obtain baseline and postcolonoscopy laboratory measurements in patients with known or suspected electrolyte disorders.^{212 213} (See Adequate Patient Monitoring under Cautions.)

Renal Effects

Renal failure and acute phosphate nephropathy (nephrocalcinosis) reported with oral sodium phosphates preparations used for bowel cleansing (i.e., Fleet Phospho-soda, Fleet Phospho-soda ACCU-PREP, OsmoPrep, Visicol);^{212 213 220 221 236 238 239 b} onset of kidney injury occurred from several hours to 21 days after use.²³⁹ May cause permanent renal function impairment and/or require long-term dialysis.^{212 213}

Increased risk of acute phosphate nephropathy associated with hypovolemia, baseline renal disease, bowel obstruction, active colitis, increased age (>55 years of age), known or suspected electrolyte disturbances (e.g., dehydration),²²⁰ and use of drugs that affect renal perfusion or function (e.g., diuretics, ACE inhibitors, angiotensin II receptor antagonists, possibly NSAIAs).^{212 213 220 239 240} (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.²³⁹

Obtain baseline and postcolonoscopy laboratory measurements in patients at increased risk of acute phosphate nephropathy.^{212 213} (See Adequate Patient Monitoring under Cautions.) Use oral sodium phosphates preparations with caution in patients with dehydration or history of acute phosphate nephropathy.^{212 213 239}

Because of potentially severe adverse renal effects, FDA is requiring manufacturer of OsmoPrep and Visicol to add a boxed warning to the labeling; develop and implement a risk management plan (Risk Evaluation and Mitigation Strategy, REMS), including medication guide; and conduct a postmarketing clinical trial to further assess risk of acute kidney injury.²³⁹

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; FDA intends to remove the indication for bowel cleansing from labeling of these preparations.^{239 240} At least one manufacturer (Fleet Laboratories) ceased distribution and initiated a voluntary recall of some OTC oral sodium phosphates preparations used for bowel cleansing (i.e., Fleet Phospho-soda Oral Saline Laxative, Fleet Phospho-soda EZ-PREP Bowel Cleansing System) effective December 12, 2008.^{x y z}

Health-care professionals should cease recommending OTC oral sodium phosphates preparations for bowel cleansing and should have removed these preparations from pharmacy shelves.^{x y} 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).^y OTC oral sodium phosphates preparations will continue to be available for use as laxatives (i.e., for relief of constipation).^{239 240}

Seizures

Rarely, generalized tonic-clonic seizures and/or loss of consciousness reported with sodium phosphates preparations; associated with electrolyte abnormalities and low serum osmolality.^{212 213} (See Electrolyte Abnormalities under Cautions.) Resolved with correction of fluid and electrolyte abnormalities.^{212 213}

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).^{212 213} (See Specific Drugs under Interactions.) Obtain baseline and postcolonoscopy laboratory measurements in such patients.^{212 213} (See Adequate Patient Monitoring under Cautions.)

Cardiac Effects

Prolonged QT interval and arrhythmias reported with sodium phosphates preparations; associated with severe electrolyte imbalance (e.g., hypokalemia, hypocalcemia).^{212 213 220} (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).^{212 213} (See Drugs that Prolong QT Interval under Interactions.) Obtain baseline and postcolonoscopy laboratory measurements, including ECGs, in such patients.^{212 213} (See Adequate Patient Monitoring under Cautions.)

Use sodium phosphates with caution in patients with CHF,^{212 213 220 221} ascites,^{212 213} acute MI,^{220 221} unstable angina,^{212 213 220 221} and recent cardiac surgery (including CABG).²¹² Some manufacturers state that sodium phosphates preparations are contraindicated in patients with CHF ^{219 220 221 227 228 229 230} or ascites.^{219 220 221 227 228}

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

GI Effects

Use oral sodium phosphates preparations with caution in patients with toxic megacolon,^{212 213} gastric retention,^{212 213} ileus,^{212 213} acute bowel obstruction,^{212 213} pseudo-obstruction of the bowel,^{212 213} severe chronic constipation,^{212 213} delayed bowel emptying,²³⁹ acute colitis,²³⁹ bowel perforation,^{212 213} gastric bypass,^{212 213} stapling surgery,^{212 213} colostomy or ileostomy,^{219 220 221} or hypomotility syndrome.^{212 213} Obtain baseline and postcolonoscopy laboratory measurements in such patients.^{212 213 220 221} (See Adequate Patient Monitoring under Cautions.) Some manufacturers state that sodium phosphates preparations are contraindicated in patients with known or suspected GI obstruction,^{219 220 221 227 228} congenital or acquired megacolon,^{219 220 221 227 228} perforation,^{220 221} or ileus.^{220 221}

Sodium phosphates preparations may induce colonic mucosal aphthous ulceration; consider in patients with known or suspected inflammatory bowel disease.^{212 213}

Possible increased sodium phosphate absorption during an acute exacerbation of chronic inflammatory bowel disease; use with caution.^{212 213} Some manufacturers state that sodium phosphates preparations are contraindicated in patients with active inflammatory bowel disease.^{220 221}

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.²¹⁸

When magnesium citrate or sodium phosphates is used in regimens with bisacodyl, consider the cautions, precautions, and contraindications associated with bisacodyl.^{221 222 223 229 230}

General Precautions

Fluid Intake

Inadequate fluid intake may lead to excessive fluid loss, hypovolemia, and dehydration;^{212 213 220 221} may be associated with acute renal failure.²²⁰ (See Renal Effects under Cautions.)

Obtain baseline and postcolonoscopy laboratory measurements in dehydrated patients or those unable to take oral fluids.^{220 221} (See Adequate Patient Monitoring under Cautions.)

Dehydration from purgation exacerbated by inadequate oral fluid intake,^{212 213 220 221} nausea,²²⁰ vomiting,^{212 213 220} and/or use of diuretics or other drugs.^{212 213 220 221} (See Specific Drugs under Interactions.)

Patients must have adequate fluid intake before, during, and after bowel cleansing regimens.^{212 213 220 221}

Assess hydration status in patients at risk for dehydration prior to use of purgatives.^{220 221}

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.²¹²

Dietary Considerations

Magnesium laxatives not for self-medication in patients on a magnesium-restricted diet.^{215 216 217 218 225}

Carbon dioxide-releasing suppositories not for self-medication in patients on a low-salt diet.^{214 231}

Use sodium phosphates preparations with caution in patients on a low-salt diet.²²⁰

Electrolytic Content

CEO-TWO suppositories contain 164 mg (7.13 mEq) of sodium per suppository.²³¹

Each level teaspoonful of magnesium sulfate crystals contains approximately 5 g of magnesium sulfate and 495 mg (40.7 mEq) of magnesium.²²⁵

Magnesium citrate oral solution contains 0.33 mg of sodium and 3.85–4.71 mEq of magnesium per 5 mL.^{224 a}

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.^a

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).²¹⁹ Fleet Enema Extra contains 22 mg of sodium per mL (total sodium content: 4.4 g in 197 mL).²²⁸

Fleet Phospho-soda contains 556 mg (24.1 mEq) of sodium and 62.3 mEq of phosphate per 5 mL.^{220 221}

Liquid LoSo Prep contains 5 mg of sodium per kit.²²³ LoSo Prep contains 12 mg of sodium per kit.²³²

Visicol and OsmoPrep tablets contain 0.398 g of dibasic sodium phosphate and 1.102 g of monobasic sodium phosphate per tablet.^{212 213}

Specific Populations

Pregnancy

Magnesium sulfate: Category B.^c

Sodium phosphates: Category C.^{212 213}

Lactation

Magnesium sulfate may be distributed into milk in small amounts.^{a c}

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

Pediatric Use

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

Magnesium citrate preparations for bowel cleansing: Use in children <12 years of age only as directed by clinician.^{222 223 232}

Magnesium citrate for laxative use: Use in children <2 years of age only as directed by clinician.^{224 234}

Magnesium hydroxide: Not for self-medication in children <2 years of age.^{217 233 235}

Fixed combination of magnesium hydroxide and mineral oil: Not for self-medication in children <6 years of age.²¹⁸

Oral sodium phosphates preparations for bowel cleansing: Safety and efficacy not established in children <18 years of age;^{212 213 220} avoid use in such children.²³⁹

Oral magnesium sulfate preparations: Not for self-medication in children <6 years of age.²²⁵

Rectal sodium phosphates enemas: Safety and efficacy not established in children <2 years of age;²¹⁹ avoid use in such children.²²⁷

Carbon-dioxide releasing suppositories: Use in children <12 years of age only as directed by clinician.²¹⁴

Fleet prep kits: Safety and efficacy not established in children <18 years of age;²²¹ avoid use in such patients.^{229 230}

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.^{212 213 220 221} (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.²³⁹ (See Renal Effects under Cautions.)

Severe and potentially fatal cases of electrolyte disorders possible; consider risk/benefit.^{220 221} Consider baseline and postcolonoscopy laboratory measurements.^{212 213 220 221} (See Electrolyte Abnormalities and also see Adequate Patient Monitoring under Cautions.)

Hepatic Impairment

Sodium phosphates tablets: Not studied in patients with hepatic impairment.^{212 213}

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

Avoid use of sodium phosphates preparations in patients with ascites.^{219 220 221 227 228 229 230}

Renal Impairment

Sodium phosphates preparations: Use with caution in renal impairment.^{212 213 227 228} Manufacturer of OsmoPrep and Visicol states that these preparations should be used with extreme caution in patients with severe renal impairment (Cl_cr <30 mL/minute);^{212 213} however, other manufacturers state use is contraindicated in patients with clinically important renal impairment.^{219 220 221} Obtain baseline and postcolonoscopy laboratory measurements.^{212 213} (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.^b

Magnesium laxatives not for self-medication in patients with renal disease.^{215 216 217 218 222 223 225 232}

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.^b (See Electrolytic Content under Cautions.)

Common Adverse Effects

Sodium phosphates preparations: Dehydration, abdominal pain, bloating, nausea, vomiting, headache, dizziness,^{212 213 b} hyperphosphatemia, hypocalcemia, hypokalemia.²¹²

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

Magnesium citrate: Abdominal discomfort, faintness, rectal burning, mild cramps.^{222 223}

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.^{212 213 220 b}

Administer magnesium sulfate ≥2 hours before or after other drugs.²²⁵

Drugs Affecting QT Interval

Risk of prolonged QT interval and potentially serious or life-threatening arrhythmias.²¹³ Use sodium phosphates preparations with caution in combination with drugs that prolong the QT interval.^{213 220} (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.²¹³ (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.^{213 220}

Drugs Affecting Seizure Threshold

Possible increased risk of seizure when used concomitantly with sodium phosphates preparations.²¹³

Specific Drugs

Drug	Interaction	Comments
Alcohol	Possible increased risk of seizures for patients withdrawing from alcohol212 213	Use caution when administering sodium phosphates preparations concomitantly during alcohol withdrawal212 213
ACE inhibitors	Increased risk of dehydration,220 hypovolemia, or acute phosphate nephropathy212 213	Use concomitantly with caution239
Angiotensin-receptor blockers	Increased risk of dehydration,220 hypovolemia,220 and acute phosphate nephropathy212 213	Use concomitantly with caution239
Antibiotics	Possible delayed or decreased absorption from the GI tract220	Efficacy may be reduced or absent220
Anticonvulsants	Possible delayed or decreased absorption from the GI tract220	Efficacy may be reduced or absent220
Antidiabetic agents	Possible delayed or decreased absorption from the GI tract220	Efficacy may be reduced or absent220
Benzodiazepines	Possible increased risk of seizures for patients withdrawing from benzodiazepines212 213	Use caution when administering sodium phosphates preparations concomitantly during benzodiazepine withdrawal213
Diuretics	Increased risk of dehydration220 and acute phosphate nephropathy212 213	Correct electrolyte balances before treating with sodium phosphates preparations213 Administer concomitantly with caution219 220 227 228
Laxatives or purgative agents	Possible additive effects	Do not use sodium phosphates preparations with additional laxatives or purgative agents213
Lithium	Increased risk of dehydration,220 hypovolemia,220 and electrolyte abnormalities212 213
NSAIAs	Increased risk of dehydration,220 hypovolemia,220 and acute phosphate nephropathy212 213	Use concomitantly with caution220 239
Oral contraceptives	Delayed or decreased absorption from the GI tract possible220	Efficacy may be reduced or absent220
Stool softener laxatives (e.g., docusate)	Increased rate of mineral oil absorptionb	Do not use fixed combination containing magnesium hydroxide and mineral oil concurrently with docusate218
Tricyclic antidepressants (TCAs)	Possible increased risk of seizures212 213	Use caution when administered concomitantly with sodium phosphates preparations212 213

Saline Laxatives Pharmacokinetics

Absorption

Bioavailability

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

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

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

Onset

Bowel movement usually occurs within 0.5–6 hours following oral administration of magnesium- or phosphate-containing laxatives.^{215 216 217 218 220 223 224 225 232}

Bowel movement usually occurs within 5–30 minutes following rectal administration of carbon dioxide-releasing suppositories.²³¹

Bowel movement usually occurs within 1–5 minutes following administration of phosphate-containing rectal enemas.^{219 227 228}

Duration

Purgative effects of sodium phosphates tablets (e.g., Visicol, OsmoPrep) persist for 1–3 hours.^{212 213}

Distribution

Extent

Magnesium is distributed into saliva and milk in small amounts.^a

Elimination

Elimination Route

Magnesium and phosphate are excreted principally by the kidneys.^a

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.²¹³

In geriatric patients >70 years of age, plasma half-life of oral sodium phosphates tablets increased twofold.^{212 213}

Stability

Storage

Oral

Solutions

Magnesium citrate: 2–30°C;^{222 223 224} protect from excessive heat²²⁴ and freezing.^{222 224} Discard within 24 hours of opening.²²⁴

Sodium phosphates: May refrigerate; do not freeze.²²⁰

Suspensions

Magnesium hydroxide: Room temperature; avoid freezing.^{215 216 233} Keep tightly closed.^{215 216 233}

Fixed-combination magnesium hydroxide and mineral oil: Room temperature; avoid freezing.²¹⁸ Keep tightly closed.²¹⁸

Tablets

Sodium phosphates: 25°C (may be exposed to 15–30°C).^{212 213}

Tablets, Chewable

Magnesium hydroxide: Room temperature.²¹⁷

Rectal

Suppositories

CEO-TWO suppositories: 20–25°C (do not exceed 30°C).²³¹ Do not refrigerate.^{214 231}

Actions

• Precise mechanism of action not known.^b 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.^b However, isosmolarity is present at the ligament of Treitz following ingestion of hyperosmolar meals.^b

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

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

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

• Insufficient sodium biphosphate in rectal suppositories to exert an effect as a saline laxative; facilitates the chemical reaction that produces carbon dioxide (CO₂).^b Rectal suppositories containing potassium bitartrate and sodium bicarbonate also produce CO₂; promotes laxation by exerting pressure in the rectum as CO₂ expands.^{214 b} Does not alter normal peristaltic reflex.²¹⁴

Advice to Patients

• Advise patient to open and read directions for bowel cleansing preparations at least 2 days in advance of examination.^{220 229 230} Importance of following complete regimen for bowel cleansing preparations.^{222 223 229 230 232}

• Advise patients of the importance of taking the recommended fluid regimen including hydrating before, during, and after bowel cleansing regimens.^{213 221 222 223 239} Advise patients of early symptoms of dehydration (e.g., feeling thirsty, dizziness, urinating less often than normal, vomiting).^{220 221} 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).^{239 240}

• Importance of drinking 240 mL of liquid with each dose of laxative.^{212 215 216 217 218 224}

• Importance of not using additional enemas or laxatives with sodium phosphates preparations;^{213 214 220 239} importance of taking only recommended dosage.^{220 239}

• Importance of not repeating oral sodium phosphates bowel cleansing regimen within 7 days of previous use.^{213 214}

• Importance of not using more than one enema in a 24-hour period.^{219 227 228}

• 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.^{214 215 216 217 218 219 220 221 223 224 225 227 228 229 230 231 232}

• Importance of discontinuing use and informing clinician if a bowel movement does not occur or rectal bleeding occurs after use;^{214 215 216 217 218 219 220 221 223 231 232} importance of contacting clinician if no return of liquid after using enema solution.²¹⁹

• Advise patients on low-salt diets to consult clinician before using sodium phosphates laxatives.^{214 227 228}

• Importance of not using laxatives for >7 days unless directed by a clinician.^{214 215 216 217 218 219 220 221 223 225 227 228 231}

• Importance of administering proper enema solution for patient age.²¹⁹

• 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.^{213 220 221 222 223 225 228 229 230 231}

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.^{215 216 217 218 219 220 221 222 223 224 225 228 229 230 231 232}

• 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.

* 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

Saline Laxative Combinations (combination)

Routes	Dosage Forms	Strengths	Brand Names	Manufacturer
	Kit	45 mL Solution, oral, Dibasic Sodium Phosphate 900 mg/5 mL and Monobasic Sodium Phosphate 2.4 g/5 mL (Fleet Phospho-soda) 4 Tablets, enteric-coated, Bisacodyl 5 mg (Fleet Bisacodyl) 1 Suppository, rectal, Bisacodyl 10 mg (Fleet Bisacodyl)	Fleet Prep Kit 1 (combination)	Fleet
		45 mL Solution, oral, Dibasic Sodium Phosphate 900 mg/5 mL and Monobasic Sodium Phosphate 2.4 g/5 mL (Fleet Phospho-soda) 4 Tablets, enteric-coated, Bisacodyl 5 mg (Fleet Bisacodyl) 30 mL Suspension, rectal, Bisacodyl 0.33 mg/mL (Fleet Bisacodyl Enema)	Fleet Prep Kit 3 (combination)	Fleet
		300 mL Solution, oral, Magnesium Citrate 4 Tablets, enteric-coated, Bisacodyl 5 mg 1 Suppository, rectal, Bisacodyl 10 mg	Liquid LoSo Prep Bowel Cleansing System (combination)	E-Z-EM
		For solution, oral, Magnesium Citrate 18 g as Magnesium Carbonate, Citric Acid, and Potassium Citrate 4 Tablets, enteric-coated, Bisacodyl 5 mg 1 Suppository, rectal, Bisacodyl 10 mg	LoSo Prep Bowel Cleansing System (combination)	E-Z-EM
		300 mL Solution, oral, Magnesium Citrate (Tridrate) 3 Tablets, enteric-coated, Bisacodyl 5 mg (Tridrate) 1 Suppository, rectal, Bisacodyl 10 mg (Tridrate)	Tridrate Bowel Evacuant Kit( combination)	Lafayette
		For solution, oral, Magnesium Citrate 19 g 3 Tablets, enteric-coated, Bisacodyl 5 mg (Tridrate) 1 Suppository, rectal, Bisacodyl 10 mg (Tridrate)	Tridrate Dry Bowel Evacuant Kit (combination)	Lafayette

Sodium Phosphates

Routes	Dosage Forms	Strengths	Brand Names	Manufacturer
Oral	Tablet	Dibasic Sodium Phosphate (anhydrous) 0.398 g with Monobasic Sodium Phosphate (monohydrate) 1.102 g	OsmoPrep	Salix
			Visicol	Salix
Rectal	Solution	Dibasic Sodium Phosphate 36 mg/mL with Monobasic Sodium Phosphate 96 mg/mL	Fleet Enema Extra	Fleet
		Dibasic Sodium Phosphate 60 mg/mL with Monobasic Sodium Phosphate 160 mg/mL	Fleet Enema	Fleet
			Fleet Pedia-Lax Enema	Fleet

Comparative Pricing

This pricing information is subject to change at the sole discretion of DS Pharmacy. This pricing information was updated 02/2013. Actual costs to patients will vary depending on the use of specific retail or mail-order locations and health insurance copays.

OsmoPrep 1.102-0.398GM Tablets (SALIX PHARMACEUTICALS): 100/$338.80 or 300/$992.12

Visicol 1.102-0.398GM Tablets (SALIX PHARMACEUTICALS): 40/$173.99 or 120/$510.07