Which laxative is composed of magnesium hydroxide?

The correct answer is Milk of Magnesia because it is specifically composed of magnesium hydroxide, which is well-known for its laxative properties. Magnesium hydroxide works by drawing water into the intestines, which helps to soften and increase the bulk of stool, facilitating easier bowel movements. This mechanism effectively alleviates constipation.

The other options listed are different types of laxatives with unique active ingredients. Dulcolax contains bisacodyl, which is a stimulant laxative that works by stimulating the intestinal muscles to promote bowel movements. Miralax is made of polyethylene glycol, a different compound that works by retaining water in the stool to soften it. Fleets typically refers to sodium phosphate, which operates by drawing water into the colon to produce a bowel movement, but does not contain magnesium hydroxide. Each of these alternatives employs various mechanisms and ingredients to address constipation, underscoring why Milk of Magnesia is the only one specifically identified with magnesium hydroxide.