Daily OTC Pearl: Milk of Magnesia

Milk of Magnesia is a laxative thought to work by drawing water into the intestines, which can cause movement of the intestines.

OTC/Lifestyle Pearl of the Day: Milk of Magnesia

Indication: Milk of Magnesia is indicated as an antacid for the symptomatic relief of stomach discomfort, indigestion, hyperacidity, heartburn, and flatulence; and as a laxative for constipation.


  • The active ingredient includes magnesium hydroxide BP 415 mg per 5 ml suspension.
  • Dosing:
    • Laxative: Adults 30-45 ml at bedtime. Repeat nightly, reducing dose each night until constipation is relieved.
    • Antacids: Adults 5-10 ml (one or two 5 ml spoonful or fill the dosing cup to the first or second line). Repeat as necessary to a maximum of 60 ml in 24 hours.
  • For the chewable form, chew thoroughly before swallowing.
  • For the liquid form, shake the bottle well before each dose.
  • Do not use a household spoon because you may not get the correct dose.
  • If you are taking this medication for constipation, drink a full glass of water (8 ounces or 240 milliliters) with each dose.
  • Adverse events may include muscle weakness, dehydration, abdominal pain, and bloody stool.
  • Mechanism of Action: Milk of Magnesia is a laxative (osmotic-type) that is thought to work by drawing water into the intestines, an effect that helps to cause movement of the intestines.