Milk of magnesia, also known by the generic name magnesium hydroxide, is a medicine that is used as a hydrating laxative and an antacid. It is not a dairy product, but rather a milky-white liquid that is made from magnesium hydroxide, purified water, and sodium hypochlorite. This medicine usually relieves uncomfortable gastrointestinal symptoms within 30 minutes and constipation within six hours.
Treatment of Stomach Discomfort
Magnesium hydroxide is an alkaline suspension, which means that it is able to neutralize acids. When a patient swallows this medicine, the hydroxide ions in it react with the hydrogen ions in stomach acid, transforming both into water. This makes milk of magnesia effective in fighting excess stomach acid, which can cause indigestion, heartburn, and stomach ulcers. When used as an antacid, the usual adult dose is from 0.02 – 0.05 oz (500 mg to 1,500 mg).
Treatment of Constipation
The magnesium in milk of magnesia is what makes it an effective laxative. The mineral ions draw water into the intestinal tract from the surrounding body tissues. This extra water softens and increases the volume of feces, which stimulates the nerves in the intestines and causes a bowel movement. For the treatment of constipation, an adult dose is between 0.07 – 0.18 oz (2,000 mg and 5,000 mg).
Many people use this product in a number of off-label ways, including as a topical treatment for dandruff, seborrheic dermatitis, acne, and other skin conditions. It reportedly can help reduce body odor as well. There are few if any scientific studies that support these claims, but using milk of magnesia on the skin is unlikely to cause any serious side effects in most people.
Milk of magnesia can react with certain antibiotics, and may be harmful to fetuses or newborns. Patients who are taking antibiotics, or who are pregnant or nursing, need to consult with a medical professional before taking this type of medicine. As with any other medication, milk of magnesia does occasionally produce side effects, including weakness, nausea, vomiting, and diarrhea. Most patients tolerate it well, so those with severe side effects should be sure to contact a healthcare provider. All patients should only use magnesium hydroxide for up to one week, unless otherwise instructed by a medical professional.
Patients with severe or chronic kidney disease are typically advised to limit their intake of magnesium, so they should only use milk of magnesia under the orders of a healthcare provider who is familiar with the condition. Healthy kidneys remove this mineral from the body quickly while unhealthy kidneys may not be able to effectively do so. This could lead to toxic levels in the blood, a condition called hypermagnesemia.
The first documented medical use of magnesium as a treatment for stomach problems was by Sir James Murray, who created a liquid suspension of this mineral in 1829. The original formula for magnesium hydroxide was developed in 1880 by a man named Charles Henry Phillips. It was sold under the brand Phillips' Milk of Magnesia.
Milk of magnesia is sold over the counter. It comes in the traditional liquid suspension, as well as chewable tablets and capsules, and may be unflavored or flavored, usually in mint or cherry. Health professionals often recommend taking it with a full glass of juice or water to help with absorption.