Unless a doctor recommends it, an antacid should not be taken more than occasionally. Aluminum hydroxide and other aluminum compounds are weak though effective antacids but can cause antacids and can cause constipation. They are frequently sold in combination with magnesium compounds, which are stronger antacids that can cause diarrhea. Sodium bicarbonate, available as baking soda, is a potent neutralizer of stomach acid. It cvan upset the balance between acids and bases in the blood and the sodium can contribute to high blood pressure.
Magnesium compounds are less strong than sodium bicarbonate but act quickly.
They may cause diarrhea. Calcium carbonate is strong and fast acting, but may the formation of kidney stones and can cause constipation. Calcium antacids may also cause ''acid rebound'' - an increase in stomach acid after the drug's effects have worn off. What happens in so-called heartburn is that there is a drop in pressure in the lower part of the esophagus, the tube that carries food from the mouth to the stomach. Normally, a high-pressure zone at the lower end of the tube prevents the acid contents of the stomach from coming up.