|Trade names||Pepcid, Zantac 360, others|
|By mouth, intravenous|
|Bioavailability||40–45% (by mouth)|
|Elimination half-life||2.5–3.5 hours|
|Excretion||Kidney (25–30% unchanged [Oral])|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||337.44 g·mol−1|
|3D model (JSmol)|
Famotidine, sold under the brand name Pepcid among others, is a histamine H2 receptor antagonist medication that decreases stomach acid production. It is used to treat peptic ulcer disease, gastroesophageal reflux disease, and Zollinger-Ellison syndrome. It is takenby mouth or by injection into a vein. It begins working within an hour.
Common side effects include headache, intestinal upset, and dizziness. Serious side effects may include pneumonia and seizures. Use in pregnancy appears safe but has not been well studied while use during breastfeeding is not recommended.
Famotidine was patented in 1979 and came into medical use in 1985. It is available as a generic medication. In 2019, it was the 104th most commonly prescribed medication in the United States, with more than 6 million prescriptions.
- Relief of heartburn, acid indigestion, and sour stomach
- Treatment for gastric and duodenal ulcers
- Treatment for pathologic gastrointestinal hypersecretory conditions such as Zollinger–Ellison syndrome and multiple endocrine adenomas
- Treatment for gastroesophageal reflux disease (GERD)
- Treatment for esophagitis
- Part of a multidrug regimen for Helicobacter pylori eradication, although omeprazole may be somewhat more effective.
- Prevention of NSAID-induced peptic ulcers.
- Given to surgery patients before operations to reduce the risk of aspiration pneumonitis.
Mechanism of action
Activation of H2 receptors located on parietal cells stimulates proton pumps to secrete acid into the stomach lumen. Famotidine, an H2 antagonist, blocks the action of histamine on the parietal cells, ultimately reducing acid secretion into the stomach.
Unlike cimetidine, the first H2 antagonist, famotidine has a minimal effect on the cytochrome P450 enzyme system, and does not appear to interact with as many drugs as other medications in its class. Some exceptions include antiretrovirals such as atazanavir, chemotherapeutics such as doxorubicin, and antifungal medications such as itraconazole. 
Famotidine was developed by Yamanouchi Pharmaceutical Co. It was licensed in the mid-1980s by Merck & Co. and is marketed by a joint venture between Merck and Johnson & Johnson. The imidazole ring of cimetidine was replaced with a 2-guanidinothiazole ring. Famotidine proved to be nine times more potent than ranitidine, and thirty-two times more potent than cimetidine.
In the United States and Canada, a product called Pepcid Complete, which combines famotidine with an antacid in a chewable tablet to quickly relieve the symptoms of excess stomach acid, is available. In the UK, this product was known as PepcidTwo until its discontinuation in April 2015.
Famotidine has poor bioavailibility (50%) due to low gastroretention time. Famotidine is less soluble at higher pH, and when used in combination with antacids gastroretention time is increased. This promotes local delivery of these drugs to receptors in the parietal cell membrane and increases bioavailibility. Researchers are developing tablet formulations that rely on other gastroretentive drug delivery systems such as floating tablets to further increase bioavailibility.
Society and culture
Certain preparations of famotidine are available over the counter (OTC) in various countries. In the United States and Canada, 10 mg and 20 mg tablets, sometimes in combination with an antacid, are available OTC. Larger doses still require a medical prescription.
Clinical trials have reported that a high dose of famotidine was found to decrease inflammation and alleviate symptoms of Covid-19 earlier. Two reviews in 2021 found famotidine to have "no significant protective effect in reducing the risk of developing serious illness, death, and intubation for COVID-19 patients", calling for further studies.
- "Famotidine tablet". DailyMed. Archived from the original on 14 July 2017. Retrieved 6 March 2021.
- "Zantac 360- famotidine tablet, film coated". DailyMed. 17 May 2022. Archived from the original on 6 July 2022. Retrieved 6 July 2022.
- "Famotidine Monograph for Professionals". Drugs.com. American Society of Health-System Pharmacists. Archived from the original on 17 June 2019. Retrieved 3 March 2019.
- British national formulary : BNF 76 (76 ed.). Pharmaceutical Press. 2018. pp. 74–75. ISBN 9780857113382.
- "Famotidine Use During Pregnancy". Drugs.com. Archived from the original on 9 February 2018. Retrieved 3 March 2019.
- Fischer J, Ganellin CR (2006). Analogue-based Drug Discovery. John Wiley & Sons. p. 444. ISBN 9783527607495. Archived from the original on 2020-07-29. Retrieved 2020-05-07.
- "The Top 300 of 2019". ClinCalc. Archived from the original on 18 March 2020. Retrieved 16 October 2021.
- "Famotidine - Drug Usage Statistics". ClinCalc. Archived from the original on 17 April 2020. Retrieved 16 October 2021.
- Kanayama S (January 1999). "[Proton-pump inhibitors versus H2-receptor antagonists in triple therapy for Helicobacter pylori eradication]". Nihon Rinsho. Japanese Journal of Clinical Medicine. 57 (1): 153–6. PMID 10036954.
- Soga T, Matsuura M, Kodama Y, Fujita T, Sekimoto I, Nishimura K, et al. (August 1999). "Is a proton pump inhibitor necessary for the treatment of lower-grade reflux esophagitis?". Journal of Gastroenterology. 34 (4): 435–40. doi:10.1007/s005350050292. PMID 10452673. S2CID 22115962.
- Borody TJ, Andrews P, Fracchia G, Brandl S, Shortis NP, Bae H (October 1995). "Omeprazole enhances efficacy of triple therapy in eradicating Helicobacter pylori". Gut. 37 (4): 477–81. doi:10.1136/gut.37.4.477. PMC 1382896. PMID 7489931.
- Hu FL, Jia JC, Li YL, Yang GB (2003). "Comparison of H2-receptor antagonist- and proton-pump inhibitor-based triple regimens for the eradication of Helicobacter pylori in Chinese patients with gastritis or peptic ulcer". The Journal of International Medical Research. 31 (6): 469–74. doi:10.1177/147323000303100601. PMID 14708410. S2CID 25818901.
- Kirika NV, Bodrug NI, Butorov IV, Butorov SI (2004). "[Efficacy of different schemes of anti-helicobacter therapy in duodenal ulcer]". Terapevticheskii Arkhiv. 76 (2): 18–22. PMID 15106408.
- Fujiwara Y, Higuchi K, Nebiki H, Chono S, Uno H, Kitada K, et al. (June 2005). "Famotidine vs. omeprazole: a prospective randomized multicentre trial to determine efficacy in non-erosive gastro-oesophageal reflux disease". Alimentary Pharmacology & Therapeutics. 21 (Suppl 2): 10–8. doi:10.1111/j.1365-2036.2005.02468.x. PMID 15943841. S2CID 24690061.
- La Corte R, Caselli M, Castellino G, Bajocchi G, Trotta F (June 1999). "Prophylaxis and treatment of NSAID-induced gastroduodenal disorders". Drug Safety. 20 (6): 527–43. doi:10.2165/00002018-199920060-00006. PMID 10392669. S2CID 41990751.
- Laine L, Kivitz AJ, Bello AE, Grahn AY, Schiff MH, Taha AS (March 2012). "Double-blind randomized trials of single-tablet ibuprofen/high-dose famotidine vs. ibuprofen alone for reduction of gastric and duodenal ulcers". The American Journal of Gastroenterology. 107 (3): 379–86. doi:10.1038/ajg.2011.443. PMC 3321505. PMID 22186979.
- Escolano F, Castaño J, López R, Bisbe E, Alcón A (October 1992). "Effects of omeprazole, ranitidine, famotidine and placebo on gastric secretion in patients undergoing elective surgery". British Journal of Anaesthesia. 69 (4): 404–6. doi:10.1093/bja/69.4.404. PMID 1419452.
- Vila P, Vallès J, Canet J, Melero A, Vidal F (November 1991). "Acid aspiration prophylaxis in morbidly obese patients: famotidine vs. ranitidine". Anaesthesia. 46 (11): 967–9. doi:10.1111/j.1365-2044.1991.tb09860.x. PMID 1750602.
- Jahr JS, Burckart G, Smith SS, Shapiro J, Cook DR (July 1991). "Effects of famotidine on gastric pH and residual volume in pediatric surgery". Acta Anaesthesiologica Scandinavica. 35 (5): 457–60. doi:10.1111/j.1399-6576.1991.tb03328.x. PMID 1887750. S2CID 44356956.
- "Common Side Effects of Pepcid (Famotidine) Drug Center". RxList. Archived from the original on 2019-03-06. Retrieved 2019-03-02.
- "Drugs & Medications". www.webmd.com. Archived from the original on 2019-03-06. Retrieved 2019-03-02.
- Fazio G, Vernuccio F, Grutta G, Re GL (26 April 2013). "Drugs to be avoided in patients with long QT syndrome: Focus on the anaesthesiological management". World Journal of Cardiology. 5 (4): 87–93. doi:10.4330/wjc.v5.i4.87. PMC 3653016. PMID 23675554.
- Lee KW, Kayser SR, Hongo RH, Tseng ZH, Scheinman MM (May 2004). "Famotidine and long QT syndrome". The American Journal of Cardiology. 93 (10): 1325–1327. doi:10.1016/j.amjcard.2004.02.025. PMID 15135720.
- Wang X, Boffito M, Zhang J, Chung E, Zhu L, Wu Y, et al. (September 2011). "Effects of the H2-receptor antagonist famotidine on the pharmacokinetics of atazanavir-ritonavir with or without tenofovir in HIV-infected patients". AIDS Patient Care and STDs. 25 (9): 509–515. doi:10.1089/apc.2011.0113. PMC 3157302. PMID 21770762.
- Hegazy SK, El-Haggar SM, Alhassanin SA, El-Berri EI (January 2021). "Comparative randomized trial evaluating the effect of proton pump inhibitor versus histamine 2 receptor antagonist as an adjuvant therapy in diffuse large B-cell lymphoma". Medical Oncology. 38 (1): 4. doi:10.1007/s12032-020-01452-z. PMID 33394214. S2CID 230485193.
- Lim, S. G.; Sawyerr, A. M.; Hudson, M.; Sercombe, J.; Pounder, R. E. (2007-03-31). "Short report: the absorption of fluconazole and itraconazole under conditions of low intragastric acidity". Alimentary Pharmacology & Therapeutics. 7 (3): 317–321. doi:10.1111/j.1365-2036.1993.tb00103.x. PMID 8117350. S2CID 20462864. Archived from the original on 2021-12-28. Retrieved 2021-12-28.
- US patent 4283408, Yasufumi Hirata, Isao Yanagisawa, Yoshio Ishii, Shinichi Tsukamoto, Noriki Ito, Yasuo Isomura and Masaaki Takeda, "Guanidinothiazole compounds, process for preparation and gastric inhibiting compositions containing them", issued 11 August 1981
- "Sankyo Pharma". Skyscape Mediwire. 2002. Archived from the original on 23 February 2009. Retrieved 31 October 2009.
- Howard JM, Chremos AN, Collen MJ, McArthur KE, Cherner JA, Maton PN, et al. (April 1985). "Famotidine, a new, potent, long-acting histamine H2-receptor antagonist: comparison with cimetidine and ranitidine in the treatment of Zollinger-Ellison syndrome". Gastroenterology. 88 (4): 1026–33. doi:10.1016/s0016-5085(85)80024-x. PMID 2857672.
- "PepcidTwo Chewable Tablet". Archived from the original on 18 July 2016. Retrieved 7 June 2015.
- "Formulation and Evaluation of Gastroretentive Floating Tablets of Famotidine". Farmavita.Net. 2008. Archived from the original on 29 March 2016. Retrieved 31 January 2009.
- Pepcid Complete
- "Famotidine". Medline Plus. Archived from the original on 2016-07-05. Retrieved 2018-03-21.
- "Duexis". Drugs.com. Archived from the original on 2017-07-18. Retrieved 2020-04-28.
- Brennan CM, Nadella S, Zhao X, Dima RJ, Jordan-Martin N, Demestichas BR, et al. (May 2022). "Oral famotidine versus placebo in non-hospitalised patients with COVID-19: a randomised, double-blind, data-intense, phase 2 clinical trial". Gut. 71 (5): 879–888. doi:10.1136/gutjnl-2022-326952. PMC 8844971. PMID 35144974.
- Zeidlickis, Dagnia (10 February 2022). "Famotidine clinical trial shows COVID-19 symptom reduction". Cold Spring Harbor Laboratory. Archived from the original on 21 April 2022. Retrieved 18 May 2022.
- Raghavan S, Leo MD (April 2022). "Histamine Potentiates SARS-CoV-2 Spike Protein Entry Into Endothelial Cells". Frontiers in Pharmacology. 13: 872736. doi:10.3389/fphar.2022.872736. PMC 9084361. PMID 35548336. Paper describing possible mechanism for effect of famotidine on covid by H₂R blocking
- Sun C, Chen Y, Hu L, Wu Y, Liang M, Ayaz Ahmed M, et al. (November 2021). "Does Famotidine Reduce the Risk of Progression to Severe Disease, Death, and Intubation for COVID-19 Patients? A Systemic Review and Meta-Analysis". Digestive Diseases and Sciences. 66 (11): 3929–3937. doi:10.1007/s10620-021-06872-z. PMC 7903022. PMID 33625613.
- Chiu L, Shen M, Lo CH, Chiu N, Chen A, Shin HJ, et al. (November 2021). Chen T (ed.). "Effect of famotidine on hospitalized patients with COVID-19: A systematic review and meta-analysis". PLOS ONE. 16 (11): e0259514. Bibcode:2021PLoSO..1659514C. doi:10.1371/journal.pone.0259514. PMC 8568101. PMID 34735523.
- "Famotidine". PetMD. Archived from the original on 2015-05-19. Retrieved 2015-06-07.
- Fogg TB, Semple D (29 November 2007). "Combination therapy with H2 and H1 antihistamines in acute, non compromising allergic reactions". BestBets. Manchester, England: Manchester Royal Infirmary. Archived from the original on 16 May 2011. Retrieved 26 April 2011.
|Wikimedia Commons has media related to Famotidine.|
- "Famotidine". Drug Information Portal. U.S. National Library of Medicine.