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indicationFor the treatment of peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD).
pharmacologyFamotidine, a competitive histamine H2-receptor antagonist, is used to treat gastrointestinal disorders such as gastric or duodenal ulcer, gastroesophageal reflux disease, and pathological hypersecretory conditions. Famotidine inhibits many of the isoenzymes of the hepatic CYP450 enzyme system. Other actions of Famotidine include an increase in gastric bacterial flora such as nitrate-reducing organisms.
mechanism of actionFamotidine binds competitively to H2-receptors located on the basolateral membrane of the parietal cell, blocking histamine affects. This competitive inhibition results in reduced basal and nocturnal gastric acid secretion and a reduction in gastric volume, acidity, and amount of gastric acid released in response to stimuli including food, caffeine, insulin, betazole, or pentagastrin.
toxicityIntravenous, mouse: LD50 = 244.4mg/kg; Oral, mouse: LD50 = 4686 mg/kg. Symptoms of overdose include emesis, restlessness, pallor of mucous membranes or redness of mouth and ears, hypotension, tachycardia and collapse.
absorptionThe bioavailability of oral doses is 40-45%.
half life2.5-3.5 hours
route of eliminationRenal clearance is 250-450 mL/min, indicating some tubular excretion.
drug interactionsAtazanavir: This gastric pH modifier decreases the levels/effects of atazanavir
Cefditoren: H2-Antagonists such as famotidine may decrease the serum concentration of cefditoren. Cefditoren prescribing information recommends to avoid concomitant use with H2-antagonists (eg, famotidine, ranitidine) and antacids as well. Consider alternative methods to minimize/control acid reflux (eg, diet modification) or alternative antimicrobial therapy if use of H2-antagonists can not be avoided.
Enoxacin: Famotidine may decrease the absorption of enoxacin.
Itraconazole: The H2-receptor antagonist, famotidine, may decrease the absorption of itraconazole.
Ketoconazole: The H2-receptor antagonist, famotidine, may decrease the absorption of ketoconazole.