Name: Famotidine (Pepcid)
Class: H2 Receptor Antagonist
Mechanism: Competitive inhib. of the histamine H2 receptor, but not of the H1 receptor ® inhib. of fasting and stim. acid secretion. No disruption of circadian rhythm of acid secretion. Inhib. of 80-90% of gastrin and vagal-stim. acid secretion.
Absorption: Oral ® rapid, good absorption. Single nighttime dose.
Dist.:
Metabolism.: Partial hepatic Metabolism.
Excretion, t½: Excreted intact in urine. 1.5-3 hr.
Toxicity/S.E.s: Uncommon. Diarrhea, headaches, myalgias, skin rashes. Occasional cardiac arrhythmias (more common than in other H2RAs).
Utility: PUD, Zollinger-Ellison synd., acute stress ulcers, GERD
Special Features: Potency—famotidine > ranitidine/nizatidine > cimetidine. Tachyphylaxis—50% less effective after 6 months. Rebound hypersecretion 2° to receptor upregulation and inhib. of ATPase recycling.