OverviewDosageSide EffectsInteractionsHalf-Life

Generic Name: Famotidine
Brands: Pepcid, Pepcid AC, Pepcid AC Maximum, Act, Dyspep HB, Fluxid, Acid Controller
Class: H2 (histamine-2) blocker
Availability: Prescription and over the counter
Molecular Formula: C8H15N7O2S3
Substance UNII: 5QZO15J2Z8

What is Famotidine?

Famotidine is a histamine-2 (H2) blocker (aka a histamine H2-receptor antagonist). It is often sold under the brand names Pepcid, Pepcid AC, Pepcid AC Maximum, Act, Dyspep HB, Fluxid, and Acid Controller.

What is Famotidine Used For?

Famotidine is used in adults and children weighing at least 40 kg (roughly 88 pounds) to treat:

  • active duodenal (upper small intestine) ulcers and active gastric (stomach) ulcers,
  • symptomatic non-erosive gastroesophageal reflux disease (GERD), and
  • erosive esophagitis due to GERD.
  • Under close supervision of a physician it can be given to infants and other children
  • Prophylaxis in the hospital for GERD
  • Some instances Peptic Ulcer Disease

It can also be used to prevent intestinal and gastric ulcers from coming back after they have healed.

In adults, famotidine can treat pathological hypersecretory conditions, which are conditions involving excessive secretion of stomach acid. These conditions include Zollinger-Ellison syndrome (tumor formation in the duodenum and/or pancreas) and multiple endocrine neoplasias (MEN) syndromes (endocrine system syndromes, most often involving tumors that can either be cancerous or non-cancerous).

In addition, famotidine can relieve symptoms such as:

  • a cough that doesn’t go away,
  • stomach pain,
  • heartburn, and
  • difficulty swallowing.

How Does Famotidine Work?

Famotidine works to reduce the amount of acid in the stomach. Specifically, it binds to certain receptors (histamine H2 receptors) in the lining of the stomach. This action prevents histamine from binding to these sites. When histamine—which helps stimulate stomach acid production—cannot bind to these receptors, stomach acid production decreases.

How Long Does it Take for Famotidine to Work?

Famotidine starts suppressing stomach acid within an hour of taking it. Depending on the dosage, this drug is most effective within one to three hours after taking a dose. In fact, its effects can last for 10 to 12 hours after a single dose. 

Famotidine relieves symptoms of GERD effectively within 24 hours after starting therapy.

Do Not Use Famotidine If:

There are several situations where this medication may not be the right choice for you.

According to the U.S. National Library of Medicine, people who should not use famotidine include patients with a history of serious hypersensitivity reactions, such as anaphylaxis, to famotidine or other histamine-2 (H2) receptor antagonists.

In addition, before taking this medication, you should consult your doctor if:

  • if you have pain when swallowing food, you are vomiting with blood, or have bloody or black stools, as these may be signs of a serious condition
  • if you have kidney disease
  • if you are already taking with other acid reducers
  • if you have had heartburn for more than 3 months
  • if you have heartburn with lightheadedness, sweating, or dizziness
  • if you have chest pain or shoulder pain with shortness of breath, sweating and pain spreading to arms, neck or shoulders
  • if you are pregnant or breastfeeding.

Please note that this list may not be complete, and there may be other situations where famotidine use is not advisable.

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

More About Famotidine


Written by

Fact Checked by