Famotidine

Famotidine
Clinical data
Pronunciation	/fəˈmɒtɪdiːn/
Trade names	Pepcid, Zantac 360, others
AHFS/Drugs.com	Monograph
MedlinePlus	a687011
License data	US DailyMed: Famotidine;
Pregnancy; category	AU: B1;
Routes of; administration	By mouth, intravenous
Drug class	Histamine H2 receptor antagonist
ATC code	A02BA03 (WHO) ;
Legal status
Legal status	AU: S3 (Pharmacist only) / S4; UK: POM (Prescription only); US: OTC / Rx-only;
Pharmacokinetic data
Bioavailability	40–45% (by mouth)
Protein binding	15–20%
Onset of action	90 minutes
Elimination half-life	2.5–3.5 hours
Duration of action	9 hours
Excretion	Kidney (25–30% unchanged [Oral])
Identifiers
	IUPAC name 3-[({2-[(diaminomethylidene)amino]-1,3-thiazol-4-yl}methyl)sulfanyl]-N-sulfamoylpropanimidamide;
CAS Number	76824-35-6 ;
PubChem CID	3325;
IUPHAR/BPS	7074;
DrugBank	DB00927 ;
ChemSpider	3208 ;
UNII	5QZO15J2Z8;
KEGG	D00318 ;
ChEBI	CHEBI:4975 ;
ChEMBL	ChEMBL902 ;
PDB ligand	FO9 (PDBe, RCSB PDB);
CompTox Dashboard (EPA)	DTXSID5023039 ;
ECHA InfoCard	100.116.793
Chemical and physical data
Formula	C8H15N7O2S3
Molar mass	337.44 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES NS(=O)(=O)/N=C(\N)CCSCc1csc(n1)N=C(N)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) ; Key:XUFQPHANEAPEMJ-UHFFFAOYSA-N ;
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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 2022, it was the 49th most commonly prescribed medication in the United States, with more than 13 million prescriptions.