Famotidine: uses, dosing, side effects & brands

Famotidine is a histamine-2 receptor antagonist used to treat Duodenal Ulcer, Dyspepsia, Peptic Esophagitis, Gastroesophageal Reflux.

The FDA classifies famotidine as a histamine-2 receptor antagonist. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

The label's §8.1 risk summary states that available data with H2-receptor antagonists, including famotidine, in pregnant women are insufficient to establish a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. Animal reproduction studies in rats and rabbits revealed no significant evidence of impaired fertility or harm to the fetus, though there are no adequate or well-controlled studies in pregnant women. Because animal studies are not always predictive, the label says the drug should be used during pregnancy only if clearly needed. Discuss use in pregnancy with your prescriber. This is what famotidine's FDA label says; whether to use it in pregnancy is your prescriber's decision.

The elimination half-life of famotidine is 2.5 to 3.5 hours — that is how long the body takes to clear half of a dose. This is the elimination half-life stated in §12.3 of the FDA label for adults with normal organ function; the label reports a single elimination half-life and does not separate a distribution from a terminal phase. Famotidine is not a prodrug, and it has no active metabolite that outlasts it — the label says the only metabolite identified in humans is the S-oxide, and famotidine undergoes minimal first-pass metabolism, with 25-30% of an oral dose recovered in urine unchanged. Kidney impairment: famotidine is cleared mostly by the kidneys (65-70% renal), and clearance falls in kidney impairment, so the drug lingers longer. The current label quantifies this as exposure rather than half-life — AUC increases at least 2-fold with moderate impairment (creatinine clearance 30-60 mL/min) and at least 5-fold with severe impairment (below 30 mL/min) — and it does not state a specific prolonged half-life number, so none is given here. Older adults: the label names no separate half-life, but notes famotidine is substantially excreted by the kidney and that risk of adverse reactions may be greater in elderly patients, particularly those with impaired renal function. Liver impairment: this label states no hepatic pharmacokinetic data and no half-life for liver impairment. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run famotidine against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

We track 7 famotidine-containing products in the U.S.: Famotidine, Fluxid, Pepcid Ac, Pepcid Preservative Free, Pepcid Preservative Free in Plastic Container, Pepcid Rpd and Pepcid. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.

Across the brands we track, famotidine is currently marketed as injectable, solution, powder, tablet and tablet, orally disintegrating, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

Yes. Our catalog lists 1 generic famotidine product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.

The FDA's Enforcement database lists 1 recall record whose product description mentions famotidine. The most recent: Famotidine Injection (Nov 6, 2025). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

Other medicines: we hold source-cited interaction answers for Can you take famotidine with omeprazole? and Can you take Tums and Pepcid together?. This is what the FDA label and our cited sources say — it is not a complete list. Your pharmacist can check your own combination.

Famotidine is an H2 blocker that reduces stomach acid. Over-the-counter, it's approved to relieve and prevent heartburn and acid indigestion (sold as Pepcid AC and store brands). By prescription, it's FDA-approved to treat and prevent stomach and duodenal ulcers, treat gastroesophageal reflux disease (GERD) including erosion of the esophagus, and manage rare conditions that cause the stomach to make too much acid, such as Zollinger-Ellison syndrome. It works by blocking histamine's signal to acid-producing cells in the stomach lining.

Both cut stomach acid, but they work differently and at different speeds. Famotidine is an H2 blocker that starts working within about an hour and is good for occasional or as-needed heartburn. Omeprazole and other proton pump inhibitors (PPIs) shut down acid production more completely but take one to four days to reach full effect, so they're used for frequent heartburn (two or more days a week) and for healing conditions like erosive esophagitis. Some people use famotidine for quick, situational relief and a PPI for ongoing daily control.

Yes, but as an off-label add-on rather than an FDA-approved use. Because famotidine blocks histamine at H2 receptors, doctors sometimes combine it with a standard H1 antihistamine (like cetirizine or diphenhydramine) for hives (urticaria) or as premedication before infusions to blunt allergic reactions. On its own it is not a treatment for a serious allergic reaction — anaphylaxis is a medical emergency treated with epinephrine. Use famotidine this way only under a clinician's direction.