magnesium hydroxide (OTC)

Brand and Other Names:Milk of Magnesia
  • Print

Dosing & Uses

AdultPediatric

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
Next:

Interactions

Interaction Checker

and magnesium hydroxide

No Results

     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

            All Interactions Sort By:
             activity indicator 
            Previous
            Next:

            Adverse Effects

            Frequency Not Defined

            Abdominal cramping

            Diarrhea

            Electrolyte imbalance

            Hypotension

            Muscle weakness

            Respiratory depression

            Previous
            Next:

            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

            Previous
            Next:

            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.

            Previous
            Next:

            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)

            Previous
            Next:

            Images

            Previous
            Next:
            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.