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Generic name: famotidine [ fam-OH-ti-deen ]
Brand names: Pepcid, Zantac 360
Drug class: H2 antagonists

Medically reviewed by Sanjai Sinha, MD. Last updated on Aug 23, 2023.

What is famotidine?

Famotidine is a histamine-2 blocker that works by decreasing the amount of acid the stomach produces.

Famotidine is used to treat and prevent ulcers in the stomach and intestines. It also treats conditions in which the stomach produces too much acid, such as Zollinger-Ellison syndrome.

Famotidine also treats gastroesophageal reflux disease (GERD) and other conditions in which acid backs up from the stomach into the esophagus, causing heartburn.

The Zantac 360 brand of this medicine does not contain ranitidine, a medicine that was withdrawn from market in the United States.


Before taking famotidine, tell your doctor if you have kidney or liver disease, a history of Long QT syndrome, stomach cancer or other problems, or asthma, COPD, or other breathing problems.

Famotidine may be only part of a complete program of treatment that also includes changes in diet or lifestyle habits. Follow your doctor's instructions very closely.

Heartburn is often confused with the first symptoms of a heart attack. Seek emergency medical attention if you have chest pain or heavy feeling, pain spreading to the jaw, arm or shoulder, nausea, sweating, anxiety, light-headedness and a general ill feeling.

Before taking this medicine

You should not use this medicine if you are allergic to famotidine or similar medicines such as ranitidine (Zantac), cimetidine (Tagamet), or nizatidine (Axid).

To make sure this medicine is safe for you, tell your doctor or pharmacist if you have ever had:

  • kidney disease;

  • liver disease;

  • cancer stomach; or

  • long QT syndrome (in you or a family member).

Ask a doctor before using famotidine if you are pregnant or breastfeeding.

How should I take famotidine?

Use famotidine exactly as directed on the label, or as prescribed by your doctor.

Famotidine oral is taken by mouth.

Famotidine injection is given as an infusion into a vein. A healthcare provider will give you this injection if you are unable to take the medicine by mouth.

You may take famotidine oral with or without food.

Shake the bottle of Pepcid suspension (liquid) vigorously for 5 to 10 seconds prior to each use. Measure the liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Most ulcers heal within 4 weeks of treatment, but it may take up to 8 weeks of using this medicine before your ulcer heals. Keep using the medication as directed.

Call your doctor if the condition you are treating with this medicine does not improve, or if it gets worse while using this medicine.

Famotidine may be only part of a complete program of treatment that also includes changes in diet or lifestyle habits. Follow all instructions of your doctor or dietitian.

Store at room temperature away from moisture, heat, and light. Do not allow the liquid medicine to freeze.

Throw away any unused liquid that is older than 30 days.

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.

What to avoid

Avoid drinking alcohol. It can increase the risk of damage to your stomach.

Avoid taking other stomach acid reducers unless your doctor has told you to. However, you may take an antacid (such as Maalox, Mylanta, Gaviscon, Milk of Magnesia, Rolaids, or Tums) with famotidine.

Famotidine side effects

Get emergency medical help if you have any signs of an allergic reaction to famotidine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

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

  • confusion, hallucinations, agitation, lack of energy;

  • a seizure;

  • fast or pounding heartbeats, sudden dizziness (like you might pass out); or

  • unexplained muscle pain, tenderness, or weakness especially if you also have fever, unusual tiredness, and dark colored urine.

Some side effects may be more likely in older adults and in people who have severe kidney disease.

Common famotidine 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.

What other drugs will interact with famotidine?

Famotidine oral can make it harder for your body to absorb other medicines you take by mouth. Tell your doctor if you are taking:

  • cefditoren;

  • dasatinib;

  • delavirdine;

  • fosamprenavir; or

  • tizanidine (if you are taking famotidine liquid).

This list is not complete. Other drugs may interact with famotidine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Popular FAQ

Famotidine starts to block stomach acid within 15 minutes to 1 hour of taking the medicine. The maximum effect usually occurs within 1 to 3 hours, and lasts for 10 to 12 hours after a single dose. It will also work to prevent heartburn if taken 10 to 60 minutes before a meal. Do not take more than 2 tablets in 24 hours.

In general, you can take over-the-counter (OTC) famotidine (Pepcid AC, Zantac 360) at any time of the day or night to help treat heartburn symptoms. Studies have shown it is best to take OTC famotidine 1 hour before an evening meal to help prevent heartburn and indigestion in the evening and during bedtime which may interfere with your sleep. Talk to your healthcare provider if your symptoms are severe or ongoing after 14 days.

The maximum daily dose of over-the-counter (OTC) famotidine (Pepcid AC, Zantac 360) in adults and children over 12 years of age is 40 mg per day unless your doctor prescribes it otherwise. If your symptoms persist more than 2 weeks, contact your doctor. Higher doses may be used for other conditions such as erosive esophagitis or Zollinger-Ellison Syndrome.

Famotidine is usually the first choice to treat occasional heartburn if your symptoms occur less than two times per week. It can be used as needed, provides quick relief (within 15 to 30 minutes), and is usually less expensive than omeprazole. Omeprazole may be an option if your heartburn occurs two or more days per week. Both products are available without a prescription. Continue reading

Famotidine (brand name: Pepcid AC, Zantac 360) should not be used for longer than 14 days if you are treating heartburn symptoms. Famotidine may be used for a longer period under the direction of your healthcare provider for treatment of intestinal or stomach ulcers, gastroesophageal reflux (GERD), erosive esophagitis, or other acid-related conditions. Continue reading

Yes, you could take omeprazole in the morning and famotidine at night but there are not many studies investigating this approach. Preliminary results suggest that taking your medication this way may provide superior control of gastric acid secretion at night without compromising the effectiveness of omeprazole in the morning. More research is needed. Continue reading

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Further information

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

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