A white powder, familiar as the active ingredient in milk of magnesia, used as an antacid and laxative. As an antacid it neutralises stomach acid, relieving heartburn and indigestion; in larger doses its osmotic effect draws water into the bowel, producing a gentle laxative action. It is available over the counter in liquid suspensions and chewable tablets. Because it contains magnesium, prolonged or excessive use can cause electrolyte disturbances, particularly in people with kidney disease. In food technology it is permitted as an acidity regulator and firming agent in some jurisdictions. As with all medicines, label directions should be followed.