Famotidine was patented in 1979 and came into medical use in 1985.[6] It is available as ageneric medication.[5] In 2023, it was the 33rd most commonly prescribed medication in the United States, with more than 16million prescriptions.[7][8]
Famotidine has a delayed onset of action, beginning after 90 minutes. However, famotidine has a duration of effect of at least 540 minutes (9.0 h). At its peak effect, 210 minutes (3.5 h) after administration, famotidine reduces acid secretion by 7.3 mmol per 30 minutes.[20]
Activation of H2 receptors located onparietal cells stimulatesproton pumps to secrete acid into the stomach lumen. Famotidine, anH2 antagonist, blocks the action ofhistamine on the parietal cells, ultimately reducing acid secretion into the stomach.
Famotidine was developed byYamanouchi Pharmaceutical Co.[29] It was licensed in the mid-1980s byMerck & Co.[30] and is marketed by a joint venture between Merck and Johnson & Johnson. Theimidazole ring of cimetidine was replaced with a 2-guanidinothiazole ring. Famotidine proved to be nine times more potent thanranitidine, and thirty-two times more potent thancimetidine.[31]
In the United States and Canada, a product calledPepcid Complete, which combines famotidine with anantacid in a chewable tablet to relieve the symptoms of excess stomach acid quickly, is available. In the UK, this product was known as PepcidTwo until its discontinuation in April 2015.[32]
Famotidine has poorbioavailibility (50%) due to its low solubility in the high pH of the intestines. Researchers are developing formulations that use gastroretentive drug delivery systems such as floating tablets to increase bioavailability by promoting local delivery (directly into the stomach wall) of these drugs to receptors in the parietal cell membrane.[33]
Certain preparations of famotidine are availableover-the-counter (OTC) in various countries. In the United States and Canada, 10 mg and 20 mg tablets, sometimes in combination with anantacid,[34][35] are available OTC. Larger doses still require a prescription. Famotidine is generally restricted toprescription only in the United Kingdom,[36] although the medication is legally allowed to be sold OTC to persons aged over 16 in supplies lasting no more than a fortnight.[37]
Formulations of famotidine in combination withibuprofen were marketed byHorizon Pharma under the trade name Duexis.[38]
At the start of theCOVID-19 pandemic, some doctors observed that anecdotally some hospitalized patients in China may have had better outcomes on famotidine than other patients who were not taking famotidine. This led to hypotheses about use of famotidine in treatment ofCOVID-19.[39][40] Famotidine was considered a possible treatment for COVID-19 due to its potentialanti-inflammatory effects. It was thought that famotidine could modify lung inflammation caused bycoronaviruses. However, studies have shown that famotidine is not effective in reducing mortality or improving recovery in COVID-19 patients.[41] Famotidine primarily works by blocking the effects ofhistamine and has some potential mechanisms of action that may contribute to its anti-inflammatory properties, including the inhibition of the production of certain pro-inflammatorycytokines such asTNF-alpha andIL-6.[42][43] Another hypothesis was that famotidine might activate thevagus nerve inflammatory reflex to attenuatecytokine storm.[43] Yet another hypothesis was that famotidine can reduce the activation ofmast cells and the subsequent release ofinflammatory mediators, therefore acting as amast cell stabilizer.[44][42] However, while famotidine may have some anti-inflammatory effects, there is currently insufficient evidence to support its use for treating inflammation associated with COVID-19.[41] Therefore, it is not recommended for this purpose.[45]
^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.PMID10036954.
^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.PMID10452673.S2CID22115962.
^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.PMID15106408.
^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.PMID1887750.S2CID44356956.
^Feldman M (May 1996). "Comparison of the effects of over-the-counter famotidine and calcium carbonate antacid on postprandial gastric acid. A randomized controlled trial".JAMA.275 (18):1428–1431.doi:10.1001/jama.1996.03530420056036.PMID8618369.
^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.PMID15135720.
^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.PMID33394214.S2CID230485193.
^Lim SG, Sawyerr AM, Hudson M, Sercombe J, Pounder RE (June 1993). "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.PMID8117350.S2CID20462864.
^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 fromthe original on 23 February 2009. Retrieved31 October 2009.
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