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Cimetidine

Generic Name: cimetidine (sye ME ti deen)
Brand Name: Tagamet HB, Tagamet

Medically reviewed on March 7, 2018

What is cimetidine?

Cimetidine works by decreasing the amount of acid your stomach produces.

Cimetidine is used to treat and prevent certain types of ulcer, and to treat conditions that cause the stomach to produce too much acid. Cimetidine is also used to treat gastroesophageal reflux disease (GERD), when stomach acid backs up into the esophagus and causes heartburn.

Cimetidine may also be used for purposes not listed in this medication guide.

Important Information

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

Before taking this medicine

Heartburn can mimic early symptoms of a heart attack. Get emergency medical help if you have chest pain that spreads to your jaw or shoulder and you feel anxious or light-headed.

Ask a doctor or pharmacist if it is safe for you to use cimetidine if you have:

  • a weak immune system; or

  • liver or kidney disease.

Ask a doctor before using this medicine if you are pregnant.

You should not breast-feed while using cimetidine.

Cimetidine is not approved for use by anyone younger than 16 years old.

How should I take cimetidine?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Cimetidine is usually taken with meals or at bedtime.

Take this medicine with a full glass of water.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

It may take up to 8 weeks for an ulcer to heal. Use this medicine for the full prescribed length of time, even if your symptoms quickly improve.

Your ulcer may take longer to heal if you smoke cigarettes.

Call your doctor if your symptoms do not improve, or if they get worse.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include nausea, vomiting, diarrhea, confusion, extreme weakness, or fainting.

What should I avoid while taking cimetidine?

Cimetidine can make it harder for your body to absorb other medicines you take by mouth. Avoid taking other medications within 2 hours before or 2 hours after you take cimetidine.

Ask your doctor before using an antacid, and use only the type your doctor recommends. Some antacids can make it harder for your body to absorb cimetidine.

Cimetidine side effects

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning in your eyes, skin pain, red or purple skin rash that spreads and causes blistering and peeling).

Stop using cimetidine and call your doctor at once if you have:

  • changes in mood, anxiety, agitation;

  • confusion, hallucinations;

  • breast swelling or tenderness;

  • easy bruising or bleeding, unusual weakness; or

  • jaundice (yellowing of the skin or eyes).

Common side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

What other drugs will affect cimetidine?

If you also take ketoconazole (Nizoral), take it at least 2 hours before you take cimetidine.

Ask a doctor or pharmacist before using cimetidine with any other medications, especially:

This list is not complete and many other drugs may affect cimetidine. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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