Cimetidine is an acid reducer active ingredient available in over-the-counter (OTC) medicines that relieve or prevent heartburn symptoms associated with acid indigestion and sour stomach. Cimetidine is part of a group of acid reducers called histamine-2 antagonists, or H2 blockers.
Cimetidine is approved by the U.S. Food and Drug Administration (FDA) and is safe and effective when used according to the Drug Facts label directions. Cimetidine may interact with certain prescription drugs. If you are taking a prescription asthma medicine, seizure medicine, or blood thinner, speak with a healthcare provider before using an OTC medicine containing cimetidine.