Famotidine

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Famotidine

Systematic (IUPAC) name
3-[({2-[(diaminomethylidene)amino]-1,3-thiazol-4-yl}methyl)sulfanyl]-N'-sulfamoylpropanimidamide
Clinical data
Pronunciation	/fəˈmɒtɪdiːn/
Trade names	Pepcid, others
AHFS/Drugs.com	monograph
MedlinePlus	a687011
Licence data	US FDA:link
Pregnancy category	B1 (Au), B (U.S.)
Legal status	Pharmacist only S3/S4(AU), General Availability (OTC)(UK), Over the Counter(US)
Routes of administration	Oral (tablet form)
Pharmacokinetic data
Bioavailability	40-45% (Oral)
Protein binding	15-20%
Metabolism	hepatic
Biological half-life	2.5-3.5 hours
Excretion	Renal (25-30% unchanged [Oral])
Identifiers
CAS Number	76824-35-6 Y
ATC code	A02BA03 (WHO)
PubChem	CID: 3325
IUPHAR/BPS	7074
DrugBank	DB00927 Y
ChemSpider	3208 Y
UNII	5QZO15J2Z8 Y
KEGG	D00318 Y
ChEBI	CHEBI:4975 Y
ChEMBL	CHEMBL902 Y
Chemical data
Formula	C8H15N7O2S3
Molecular mass	337.449 g/mol
SMILES O=S(=O)(N=C(N)CCSCc1nc(/N=C(/N)N)sc1)N
InChI InChI=1S/C8H15N7O2S3/c9-6(15-20(12,16)17)1-2-18-3-5-4-19-8(13-5)14-7(10)11/h4H,1-3H2,(H2,9,15)(H2,12,16,17)(H4,10,11,13,14) Y Key:XUFQPHANEAPEMJ-UHFFFAOYSA-N Y
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Famotidine, sold under the trade name Pepcid among others is a histamine H₂-receptor antagonist that inhibits stomach acid production. It is commonly used in the treatment of peptic ulcer disease and gastroesophageal reflux disease.

Unlike cimetidine, the first H₂ antagonist, famotidine has no effect on the cytochrome P450 enzyme system, and does not appear to interact with other drugs.

It was discovered in 1979.

Medical uses

• 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 (GERD)
• Treatment for Esophagitis
• Part of a multidrug regimen for H. 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.

Famotidine is also given to dogs and cats with acid reflux. Famotidine has been used in combination with an H1 antagonist to treat and prevent urticaria caused by an acute allergic reaction.

Preparations

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.

Formulations of famotidine in combination with ibuprofen were marketed by Horizon Pharma under the trade name Duexis.

Side effects

Side effects associated with famotidine use include headache, dizziness, and constipation or diarrhea.

History

Famotidine was developed by Yamanouchi Pharmaceutical Co. It was licensed in the mid-80s 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 9 times more potent than ranitidine, and 32 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 (Schwarz) or Quamatel (Gedeon Richter Ltd.).

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 prior to its discontinuation in April 2015.

Famotidine suffers from poor bioavailability (50%), as it is poorly soluble in the low pH of the stomach. When used in combination with antacids, it promotes local delivery of these drugs to the receptor of the parietal cell wall. Therefore, researchers are developing innovative formulations of tablets, such as gastroretentive drug delivery systems. Such tablets are retained in the stomach for a longer period of time, thereby improving the bioavailability of drugs. Local delivery also increases bioavailability at the stomach wall receptor site and increases the efficacy of drugs to reduce acid secretion.

Research

Famotidine has been investigated as an adjunct in treatment-resistant schizophrenia. In one trial, it caused a 10% reduction in schizophrenic symptom severity in treatment-resistant patients.

See also

• Ranitidine, another popular H2-receptor antagonist
• Nizatidine