Famotidine
Famotidine is an oral and parenteral H2-receptor antagonist used in adults and children for gastro-oesophageal reflux, peptic ulcer disease and prevention of stress ulcers. It blocks histamine-stimulated gastric acid secretion with a favourable safety profile.
- Chemical formula
- C8H15N7O2S3
- CAS number
- 76824-35-6
- ATC code
- A02BA03
- Molecular weight
- 337.45 g/mol
- Drug class
- H2-receptor antagonist
- Also known as
- MK-208, Famotidina
What is it?
Famotidine is a thiazole derivative H2-receptor antagonist approved in the 1980s. It is supplied as oral tablets, oral suspension, intravenous solution and orally disintegrating tablets. Famotidine is dispensed both with and without prescription depending on the dose and country, and is the main remaining H2-blocker after the withdrawal of ranitidine due to nitrosamine contamination concerns. The molecule is part of the World Health Organization List of Essential Medicines.
Mechanism of action
Famotidine reversibly and competitively blocks histamine H2 receptors on gastric parietal cells, reducing both basal and stimulated gastric acid secretion. The effect is most pronounced on histamine-mediated secretion, with partial reductions in vagal and gastrin-stimulated secretion. Famotidine does not significantly affect H1 or other histamine receptor subtypes and does not have anticholinergic or antiandrogenic effects, distinguishing it from cimetidine.
Pharmacokinetics
Famotidine is rapidly absorbed orally, with peak plasma concentrations reached after one to three hours. Bioavailability is approximately 40% to 45%, lower than for proton pump inhibitors. Plasma protein binding is approximately 15% to 20%. The drug is excreted predominantly unchanged in urine, with the terminal half-life of approximately 2.5 to 3.5 hours. Renal impairment requires dose adjustment, and the dosing interval is extended in advanced kidney disease.
Indications
Famotidine is approved in adults and children for short-term treatment of active duodenal and gastric ulcer, maintenance therapy of duodenal ulcer, gastro-oesophageal reflux disease, Zollinger-Ellison syndrome and other hypersecretory conditions. It is also used for occasional heartburn and dyspepsia in over-the-counter formulations. According to clinical guidelines, proton pump inhibitors are generally preferred for chronic GORD, while famotidine remains useful for episodic symptoms and selected combination regimens.
Safety profile
Famotidine is generally well tolerated. Common adverse effects include headache, dizziness and gastrointestinal symptoms. Unlike cimetidine, famotidine does not cause antiandrogenic effects and has minimal cytochrome P450 interactions. Rare adverse events include reversible bone marrow suppression and confusion in elderly patients with renal impairment. According to the prescribing information, dose adjustment is required in renal impairment, and prolonged use should be reviewed by the prescriber.
Products containing this ingredient
Frequently asked questions
How is famotidine different from omeprazole? ▾
Famotidine is an H2-receptor antagonist that reversibly blocks histamine-stimulated gastric acid secretion with rapid onset and modest acid suppression. Omeprazole is a proton pump inhibitor that irreversibly inhibits the acid pump itself, with deeper and more durable acid suppression. According to clinical guidelines, proton pump inhibitors are generally preferred for chronic GORD and erosive disease, while famotidine remains useful for occasional symptoms or as add-on therapy.
Why was ranitidine withdrawn while famotidine remained? ▾
Ranitidine, another H2-receptor antagonist, was withdrawn from many markets in 2019 to 2020 because of detection of N-nitrosodimethylamine (NDMA) impurities in some formulations and concerns about formation over time. Famotidine has a different chemical structure and has not shown the same nitrosamine concerns, so it remains widely available. According to regulatory communications, famotidine is now the predominant H2-blocker in many countries.
Can famotidine be used long-term? ▾
Famotidine can be used for prolonged periods when needed, although chronic GORD is more often managed with proton pump inhibitors. According to the prescribing information, long-term use is generally well tolerated, with periodic reassessment by the prescriber. Tachyphylaxis (reduced effect over time) is possible with chronic use, which sometimes prompts reassessment of the regimen and consideration of a proton pump inhibitor.
Is famotidine safe in older adults? ▾
Famotidine is generally well tolerated in older adults, but renal function should be considered because the drug is excreted predominantly unchanged in urine. According to the prescribing information, dose reduction or extended dosing intervals are recommended in moderate to severe renal impairment, including in many elderly patients. Confusion has been reported in older patients with reduced renal clearance and should be monitored.
What are the main contraindications for famotidine? ▾
Famotidine is contraindicated in known hypersensitivity to famotidine or other H2-receptor antagonists. Caution is required in renal impairment (with dose adjustment), in older adults, and during pregnancy and breastfeeding. According to the prescribing information, the medical history must be reviewed by a clinician before any prescription, particularly in patients with chronic kidney disease or on multiple medications.
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.