Dosing & Uses
Dosage Forms & Strengths
chewable tablet
- 311mg
- 400mg
suspension
- 7.75%
- 400mg/5mL
- 800mg/5mL
- 1200mg/15mL
- 2400mg/10mL
Constipation
Magnesium hydroxide (400 mg/5 mL): 30-60 mL/day PO at bedtime or in divided doses
Magnesium hydroxide (800 mg/5 mL): 15-30 mL/day PO at bedtime or in divided doses
Chewable tablet: 8 tablets/day PO at bedtime or in divided doses
Acid Indigestion
Magnesium hydroxide (400 mg/5 mL): 5-15 mL PO q4hr; no more than 4 doses per 24-hour period
Chewable tablet: 2-4 tablets PO q4hr; no more than 4 doses per 24-hour period
Dosage Forms & Strengths
chewable tablet
- 311mg
- 400mg
suspension
- 7.75%
- 400mg/5mL
- 800mg/5mL
- 1200mg/15mL
- 2400mg/10mL
Constipation
<2 years: Safety and efficacy not established
Suspension
- 2-6 years: 5-15 mL/day of regular-strength liquid PO at bedtime or in divided doses
- 6-12 years: 15-30 mL/day (400 mg/5 mL) or 7.5-15 mL/day (800 mg/5 mL) PO at bedtime or in divided doses
- ≥12 years: 30-60 mL/day (400 mg/5 mL) or 15-30 mL/day (800 mg/5 mL) PO at bedtime or in divided doses
Chewable tablet
- <3 years: Not recommended
- 3-6 years: 2 tablets PO once daily or in divided doses
- 6-12 years: 4 tablets PO once daily or in divided doses
- >12 years: 8 tablets PO once daily or in divided doses
Acid Indigestion
Liquid
- <12 years: Not recommended
- ≥12 years: 5-15 mL (400 mg/5 mL) PO q4hr; no more than 4 doses per 24-hour period
Chewable tablet
- <12 years: Not recommended
- ≥12 years: 2-4 tablets PO q4hr; no more than 4 doses per 24-hour period
Interactions
Interaction Checker
No Results

Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor

Contraindicated (0)
Serious - Use Alternative (13)
- baloxavir marboxil
magnesium hydroxide will decrease the level or effect of baloxavir marboxil by cation binding in GI tract. Avoid or Use Alternate Drug. Baloxavir may bind to polyvalent cations resulting in decreased absorption. Studies in monkeys showed concurrent use with calcium, aluminum, or iron caused significantly decreased plasma levels. Human studies not conducted.
- demeclocycline
magnesium hydroxide decreases levels of demeclocycline by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug.
- doxycycline
magnesium hydroxide decreases levels of doxycycline by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug.
- eltrombopag
magnesium hydroxide decreases levels of eltrombopag by inhibition of GI absorption. Applies only to oral form of both agents. Contraindicated. Separate by at least 4 hours.
- infigratinib
magnesium hydroxide will decrease the level or effect of infigratinib by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug. If use with an acid-reducing agent cannot be avoided, administer infigratinib 2 hr before and after administration of a locally-acting antacid.
- minocycline
magnesium hydroxide decreases levels of minocycline by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug.
- oxytetracycline
magnesium hydroxide decreases levels of oxytetracycline by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug.
- pazopanib
magnesium hydroxide will decrease the level or effect of pazopanib by increasing gastric pH. Applies only to oral form of both agents. Avoid or Use Alternate Drug. Avoid coadministration of pazopanib with drugs that raise gastric pH; may use short-acting antacids in place of PPIs and H2 antagonists, but separate antacid and pazopanib dosing by several hours
- ponatinib
magnesium hydroxide decreases levels of ponatinib by increasing gastric pH. Applies only to oral form of both agents. Avoid or Use Alternate Drug.
- potassium phosphates, IV
magnesium hydroxide decreases effects of potassium phosphates, IV by cation binding in GI tract. Avoid or Use Alternate Drug. Magnesium decreases serum phosphate concentration by binding dietary phosphate. Use alternatives if available.
- raltegravir
magnesium hydroxide will decrease the level or effect of raltegravir by cation binding in GI tract. Avoid or Use Alternate Drug. Magnesium containing antacids reduce raltegravir plasma levels when taken within 6 hr of raltegravir dose
- sotorasib
magnesium hydroxide will decrease the level or effect of sotorasib by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug. If use with an acid-reducing agent cannot be avoided, administer sotorasib 4 hr before or 10 hr after administration of a locally-acting antacid.
- tetracycline
magnesium hydroxide decreases levels of tetracycline by inhibition of GI absorption. Applies only to oral form of both agents. Avoid or Use Alternate Drug.
Monitor Closely (23)
- bictegravir
magnesium hydroxide will decrease the level or effect of bictegravir by cation binding in GI tract. Modify Therapy/Monitor Closely. Bictegravir can be taken under fasting conditions 2 hr before antacids containing Al, Mg, or Ca. Routine administration of bictegravir simultaneously with, or 2 hr after, antacids containing Al, Mg, or Ca is not recommended.
- cabotegravir
magnesium hydroxide will decrease the level or effect of cabotegravir by cation binding in GI tract. Modify Therapy/Monitor Closely. Administer antacid products at least 2 hr before or 4 hr after taking oral cabotegravir.
- chloroquine
magnesium hydroxide will decrease the level or effect of chloroquine by Mechanism: inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Separate doses by at least 4 hr
- ciprofloxacin
magnesium hydroxide decreases levels of ciprofloxacin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Coadministration of ciprofloxacin with multivalent cation-containing products may reduce the bioavailability of ciprofloxacin by 90%. Administer ciprofloxacin at least 2 hours before or 6 hours after using these products. Use alternatives if available.
- crizotinib
magnesium hydroxide decreases levels of crizotinib by increasing gastric pH. Applies only to oral form of both agents. Use Caution/Monitor. Drugs that elevate the gastric pH may decrease the solubility of crizotinib and subsequently reduce its bioavailability. However, no formal studies have been conducted. .
- deferiprone
magnesium hydroxide decreases levels of deferiprone by enhancing GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Deferiprone may bind polyvalent cations (eg, iron, aluminum, and zinc), separate administration by at least 4 hr between deferiprone and other medications (eg, antacids), or supplements containing these polyvalent cations.
- deflazacort
magnesium hydroxide and deflazacort both decrease serum potassium. Use Caution/Monitor.
- dolutegravir
magnesium hydroxide will decrease the level or effect of dolutegravir by cation binding in GI tract. Use Caution/Monitor. Administer dolutegravir 2 hr before or 6 hr after taking medications containing polyvalent cations; use alternative therapy if available
- fleroxacin
magnesium hydroxide decreases levels of fleroxacin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- gemifloxacin
magnesium hydroxide decreases levels of gemifloxacin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- lanthanum carbonate
lanthanum carbonate, magnesium hydroxide. cation binding in GI tract. Use Caution/Monitor. Administer antacid at least 2 hours before or after lanthanum. .
- levofloxacin
magnesium hydroxide decreases levels of levofloxacin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- moxifloxacin
magnesium hydroxide decreases levels of moxifloxacin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- ofloxacin
magnesium hydroxide decreases levels of ofloxacin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- omadacycline
magnesium hydroxide will decrease the level or effect of omadacycline by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Multivalent cation-containing products may impair absorption of tetracyclines, which may decrease its efficacy. Separate dosing of tetracyclines from these products.
- pancrelipase
magnesium hydroxide decreases effects of pancrelipase by pharmacodynamic antagonism. Use Caution/Monitor. Antacids may negate beneficial effects of enzymes.
- penicillamine
magnesium hydroxide decreases levels of penicillamine by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate by 2 hours.
- pexidartinib
magnesium hydroxide will decrease the level or effect of pexidartinib by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Separate pexidartinib by 2 hr before or after taking a locally-acting antacid.
- riociguat
magnesium hydroxide decreases levels of riociguat by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor. Separate administration by at least 1 hour.
- sarecycline
magnesium hydroxide will decrease the level or effect of sarecycline by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Multivalent cation-containing products may impair absorption of tetracyclines, which may decrease its efficacy. Separate dosing of tetracyclines from these products.
- sodium phosphates, IV
magnesium hydroxide decreases effects of sodium phosphates, IV by cation binding in GI tract. Modify Therapy/Monitor Closely. Magnesium decreases serum phosphate concentration by binding dietary phosphate. Use alternatives if available.
- vismodegib
magnesium hydroxide will decrease the level or effect of vismodegib by Other (see comment). Use Caution/Monitor. Drugs that increase gastric pH alter vismodegib solubility and therefore reduce bioavailability; effect on efficacy unknown
- vitamin D
vitamin D increases levels of magnesium hydroxide by Other (see comment). Use Caution/Monitor. Comment: Vitamin D can increase serum magnesium concentrations, particularly in the presence of renal impairment. The combined use of vitamin D and magnesium-containing products should be avoided, if possible, in patients with chronic renal failure.
Minor (41)
- amikacin
amikacin decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- amiloride
amiloride increases levels of magnesium hydroxide by decreasing renal clearance. Minor/Significance Unknown.
- amphotericin B deoxycholate
amphotericin B deoxycholate decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- bazedoxifene/conjugated estrogens
bazedoxifene/conjugated estrogens decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- bendroflumethiazide
bendroflumethiazide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- bumetanide
bumetanide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- calcitonin salmon
calcitonin salmon increases levels of magnesium hydroxide by decreasing renal clearance. Minor/Significance Unknown.
- chlorothiazide
chlorothiazide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- chlorthalidone
chlorthalidone decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- conjugated estrogens
conjugated estrogens decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- conjugated estrogens, vaginal
conjugated estrogens, vaginal decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- cyclopenthiazide
cyclopenthiazide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- dextrose
dextrose decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- dextrose (Antidote)
dextrose (Antidote) decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- digoxin
digoxin decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- doxercalciferol
doxercalciferol increases levels of magnesium hydroxide by enhancing GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- drospirenone
drospirenone increases levels of magnesium hydroxide by decreasing renal clearance. Minor/Significance Unknown.
- estradiol
estradiol decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- estrogens conjugated synthetic
estrogens conjugated synthetic decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- estrogens esterified
estrogens esterified decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- estropipate
estropipate decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- ethacrynic acid
ethacrynic acid decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- furosemide
furosemide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- gentamicin
gentamicin decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- glucagon intranasal
glucagon intranasal increases levels of magnesium hydroxide by decreasing renal clearance. Minor/Significance Unknown.
- hydrochlorothiazide
hydrochlorothiazide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- ibandronate
magnesium hydroxide decreases levels of ibandronate by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- indapamide
indapamide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- mannitol
mannitol decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- mestranol
mestranol decreases levels of magnesium hydroxide by Other (see comment). Minor/Significance Unknown. Comment: Magnesium shifted from blood to tissue storage.
- methyclothiazide
methyclothiazide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- metolazone
metolazone decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- neomycin PO
neomycin PO decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- nitrofurantoin
magnesium hydroxide decreases levels of nitrofurantoin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- paromomycin
paromomycin decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- sodium polystyrene sulfonate
sodium polystyrene sulfonate increases levels of magnesium hydroxide by decreasing renal clearance. Minor/Significance Unknown. Risk of alkalosis.
- spironolactone
spironolactone increases levels of magnesium hydroxide by decreasing renal clearance. Minor/Significance Unknown.
- streptomycin
streptomycin decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- tobramycin
tobramycin decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- torsemide
torsemide decreases levels of magnesium hydroxide by increasing renal clearance. Minor/Significance Unknown.
- triamterene
triamterene increases levels of magnesium hydroxide by decreasing renal clearance. Minor/Significance Unknown.
Adverse Effects
Frequency Not Defined
Abdominal cramping
Diarrhea
Electrolyte imbalance
Hypotension
Muscle weakness
Respiratory depression
Warnings
Contraindications
Renal failure
Existing electrolyte imbalance
Appendicitis symptoms or acute surgical abdomen
Myocardial damage or heart block
Fecal impaction or rectal fissures
Intestinal obstruction or perforation
Undiagnosed abdominal pain
Cautions
Use with caution in renal insufficiency
Pregnancy & Lactation
Pregnancy category: A
Lactation: Use in nursing mothers appears to be safe
Pregnancy Categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available.Pharmacology
Mechanism of Action
Laxative: Promotes osmotic retention of fluid, which distends the colon with increased peristaltic activity and stimulates bowel evacuation
Antacid: Reacts with hydrochloric acid in stomach to form magnesium chloride
Absorption
Bioavailability: 15-30%
Onset: 0.5-6 hr (laxative)
Elimination
Excretion: Urine (up to 30% as absorbed magnesium), feces (as unabsorbed drug)
Images
BRAND | FORM. | UNIT PRICE | PILL IMAGE |
---|---|---|---|
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Phillips Milk of Magnesia oral - | 311 mg chewable tablet | ![]() | |
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Phillips Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Dulcolax (magnesium hydroxide) oral - | 400 mg/5 mL suspension | ![]() | |
Dulcolax (magnesium hydroxide) oral - | 400 mg/5 mL suspension | ![]() | |
Dulcolax (magnesium hydroxide) oral - | 1,200 mg chewable tablet | ![]() | |
Dulcolax (magnesium hydroxide) oral - | 1,200 mg chewable tablet | ![]() | |
Dulcolax (magnesium hydroxide) oral - | 600 mg chewable tablet | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Milk of Magnesia oral - | 400 mg/5 mL suspension | ![]() | |
Pedia-Lax (mag hydroxide) oral - | 400 mg (170 mg magnesium) chewable tablet | ![]() |
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