Famotidine
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 taken by mouth or by injection into a vein. It begins working within an hour.
Common side effects include headache, abdominal pain, diarrhea or constipation, 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 2023, it was the 33rd most commonly prescribed medication in the United States, with more than 16million prescriptions.
Medical uses
- 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
- 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 pneumonia.
Pharmacokinetics
Side effects
The most common side effects associated with famotidine use include headache, dizziness, and constipation or diarrhea.Famotidine may contribute to QT prolongation, particularly when used with other QT-elongating drugs, or in people with poor kidney function.
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.Interactions
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.History
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.It was first marketed in 1981. Pepcid RPD orally disintegrating tablets were released in 1999. Generic preparations became available in 2001, e.g. Fluxid or Quamatel.
In the United States and Canada, a product called Pepcid Complete, which combines famotidine with an antacid 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.
Famotidine has poor bioavailibility 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 of these drugs to receptors in the parietal cell membrane.
Society and culture
Certain preparations of famotidine are available over-the-counter 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 prescription. Famotidine is generally restricted to prescription only in the United Kingdom, although the medication is legally allowed to be sold OTC to persons aged over 16 in supplies lasting no more than a fortnight.Formulations of famotidine in combination with ibuprofen were marketed by Horizon Pharma under the trade name Duexis.