Famotidine

From Wikipedia, the free encyclopedia

Famotidine

Clinical data
Pronunciation /fəˈmɒtɪdiːn/
Trade names Pepcid, others
AHFS/Drugs.com Monograph
MedlinePlus a687011
 US DailyMed: Famotidine
License data
 US FDA: Famotidine

 AU: B1
Pregnancy
category  US: B (No risk in non-
human studies)
Routes of
By mouth (tablets), Intravenous
administration
ATC code  A02BA03 (WHO)
Legal status
 AU: S3 (Pharmacist
only) /S4; pharmacist only
 UK: General sales list
Legal status
(GSL, OTC)

US: OTC / Rx-only

Pharmacokinetic data
Bioavailability 40–45% (by mouth)[1]
Protein binding 15–20%[1]
 Metabolism hepatic
Elimination half-
2.5–3.5 hours[1]
life
Kidney (25–30% unchanged
Excretion
[Oral])[1]
Identifiers
IUPAC name[show]
 
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
 DTXSID5023039
Dashboard (EPA)
ECHA InfoCard 100.116.793
Chemical and physical data
Formula C8H15N7O2S3
Molar mass 337.44 g·mol−1
3D model (JSmol)  Interactive image

Famotidine, sold under the brand name Pepcid among others, is a medication that
decreases stomach acid production.[2] It is used to treat peptic ulcer disease,
gastroesophageal reflux disease, and Zollinger-Ellison syndrome.[2] It is taken by
mouth or by injection into a vein.[2] It begins working within an hour.[2]

Common side effects include headache, intestinal upset, and dizziness.[2] Serious side
effects may include pneumonia and seizures.[2][3] Use in pregnancy appears safe but
has not been well studied while use during breastfeeding is not recommended.[4] It is
a histamine H2 receptor antagonist.[2]

Famotidine was patented in 1979 and came into medical use in 1985.[5] It is available
as a generic medication.[3] A month supply in the United Kingdom costs the NHS
about £30 as of 2019.[3] In the United States the wholesale cost of this amount is
about $2.[6] In 2017, it was the 115th most commonly prescribed medication in the
United States, with more than six million prescriptions.[7][8]

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 disease (GERD)
 Treatment for esophagitis
 Part of a multidrug regimen for Helicobacter pylori eradication, although
omeprazole may be somewhat more effective.[9][10][11][12][13][14]
 Prevention of NSAID-induced peptic ulcers.[15][16]
 Given to surgery patients before operations to reduce the risk of aspiration
pneumonitis.[17][18][19]

Famotidine is also given to dogs and cats with acid reflux.[20] Famotidine has been
used in combination with an H1 antagonist to treat and prevent urticaria caused by an
acute allergic reaction.[21]

Side effects

The most common side effects associated with famotidine use include headache,
dizziness, and constipation or diarrhea.[22][23]

Famotidine may contribute to QT prolongation,[24] particularly when used with other

QT-elongating drugs, or in people with poor kidney function.[25]

Mechanism of action

Activation of H2 receptors located on parietal cells stimulates the proton pump to

secrete acid. Famotidine (H2 antagonist) blocks the action of histamine in the parietal
cells, ultimately blocking acid secretion in the stomach.

Interactions

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.[26]

History

Famotidine was developed by Yamanouchi Pharmaceutical Co.[27] It was licensed in

the mid-1980s by Merck & Co.[28] 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.[29]

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.[30]

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 wall and increases bioavailibility. Researchers are
developing tablet formulations that rely on other gastroretentive drug delivery
systems such as floating tablets to further increase bioavailibility.[31]

Preparations

It is taken by mouth, as a tablet or suspension, or by injection into a vein.[2]

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,[32][33] 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.[34]

References

1.

 Truven Health Analytics, Inc. DRUGDEX® System (Internet) [cited 2013 Oct
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  US patent 4283408, Yasufumi Hirata, Isao Yanagisawa, Yoshio Ishii,
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  Pepcid Complete
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34.  "Duexis". Drugs.com.