When to Choose MiraLax, Milk of Magnesia, or Other Laxatives

Choosing Between Milk of Magnesia and MiraLax

Both MiraLax and milk of magnesia are used as laxatives and work by softening stool. However, they have different compositions.

MiraLax (a hyperosmotic laxative) increases water in the intestines so stools can exit more rapidly. The active ingredient in MiraLax is polyethylene glycol (PEG) 3350. It is an FDA-approved OTC short-term treatment of occasional constipation in those 17 and older.

MiraLax is a powder you mix into 4 to 8 ounces of liquid. One dose is 17 grams, which usually produces a bowel movement in one to three days. It can be taken once a day for up to seven days.

PEG 3350 is also available under various brand names, such as:

• GaviLax
• HealthyLax
• SmoothLax

Milk of magnesia (a saline laxative) uses sodium to draw water into the intestines to help stools pass through more easily. The active ingredient in milk of magnesia is magnesium hydroxide.

This medication is used for other purposes (e.g., heartburn, upset stomach). When used as a laxative for occasional constipation, the daily dose is as follows:

• For those aged 12 and older, the dose is 30 mL (2 tablespoons) to 60 mL (4 tablespoons).
• For ages 6 to 11, take 15 mL (1 tablespoon) to 30 mL (2 tablespoons).
• For children under age 6, consulting with a healthcare provider is recommended.

These dosages may be taken once a day, in divided doses, or as directed by your healthcare provider. Used as a laxative, milk of magnesia should produce a bowel movement within 30 minutes to six hours.

Do not use milk of magnesia for longer than seven days without medical supervision. Milk of magnesia should be shaken well before use and can be taken with a glass of water.

Brand names of this medication include:

• Phillips’ Milk of Magnesia
• Pedia-Lax Chewable Tablets
• Dulcolax Milk of Magnesia
• Ex-Lax Milk of Magnesia