Alka-Seltzer is an effervescent antacid and pain reliever that is used to treat symptoms caused by too much stomach acid such as heartburn, upset stomach, or indigestion. It contains three active ingredients: aspirin, sodium bicarbonate, and anhydrous citric acid. When the tablet is dropped in water, the acid and the baking soda react, producing effervescence that neutralizes acid on contact. The sodium in the Alka-Seltzer effervescent products plays an important role, enabling the medication to dissolve quickly in water and begin neutralizing acid as soon as ingested.

Alka-Seltzer is marketed for relief of minor aches, pains, inflammation, fever, headache, heartburn, stomachache, indigestion, acid reflux, and hangovers, while neutralizing excess stomach acid. It is available in many different flavors and sold in foil packets, each containing two tablets.

In summary, Alka-Seltzer is an antacid that works by neutralizing excess stomach acid and is used to treat symptoms caused by too much stomach acid such as heartburn, upset stomach, or indigestion.