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Cimetidine is an acid reducer active ingredient available in over-the-counter (OTC) medicines that relieves 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 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 professional before using an OTC medicine containing cimetidine.

*Please read the OTC Drug Facts label carefully for active ingredient information for specific products. 

Tips for Medicines with Cimetidine

When using cimetidine-containing medicines, it is important to know that:

  • You should never take more medicine or for a longer period of time than what the label says.

Do not use if:

  • You are allergic to cimetidine or other acid reducers.
  • You have trouble or pain swallowing food, vomiting with blood, or bloody or black stools.
  • You are currently using another acid reducer.

Ask a healthcare professional before use if:

  • You are taking the asthma medicine, theophylline.
  • You are taking the blood-thinning drug, warfarin.
  • You are taking the seizure medicine, phenytoin.
  • You have had heartburn for over three months.
  • Your heartburn is accompanied by lightheadedness, sweating, or dizziness.
  • You are experiencing chest or shoulder pain with shortness of breath; sweating; pain spreading to your arms, neck, or shoulders; or lightheadedness.
  • You have frequent chest pain, wheezing, unexplained weight loss, nausea or vomiting, or stomach pain.
  • You are pregnant or breastfeeding.

Stop use and ask a doctor if:

  • Your heartburn continues or gets worse.
  • Your stomach pain continues.
  • You need to take the medicine for more than 14 days.
  • You take too much. Immediately contact a doctor or the poison control national helpline at 800.222.1222.

If you have questions about any of the medicines you are taking or if you have any unexpected side effects, talk to a healthcare professional. And of course, keep all medicines out of the reach and sight of children.

Tips for Parents

  • Talk to a healthcare professional before giving an OTC medicine containing cimetidine to a child under the age of 12.

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