What is milk of magnesia primarily a suspension of?

Milk of magnesia is primarily a suspension of magnesium hydroxide. It is a commonly used over-the-counter antacid and laxative, known for its ability to neutralize stomach acid and provide relief from indigestion. The formulation contains magnesium hydroxide particles suspended in water, which gives it a milky appearance, hence the name "milk of magnesia."

When taken, magnesium hydroxide reacts with gastric acid to form magnesium salts and water, effectively reducing acidity in the stomach. Its effectiveness as a laxative is due to its ability to draw water into the intestines, enhancing intestinal motility. In contrast, other options, such as calcium hydroxide, magnesium sulfate, and sodium bicarbonate, serve different purposes or have different solubility and properties that make them unsuitable as the main component in this particular formulation.