indication
For the treatment of peptic ulcer disease (PUD) and gastroesophageal reflux disease (GERD).
pharmacology
Famotidine, a competitive histamine H
2-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 action
Famotidine binds competitively to H
2-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.
toxicity
Intravenous, mouse: LD
50 = 244.4mg/kg; Oral, mouse: LD
50 = 4686 mg/kg. Symptoms of overdose include emesis, restlessness, pallor of mucous membranes or redness of mouth and ears, hypotension, tachycardia and collapse.
biotransformation
Hepatic.
absorption
The bioavailability of oral doses is 40-45%.
half life
2.5-3.5 hours
route of elimination
Renal clearance is 250-450 mL/min, indicating some tubular excretion.
drug interactions
Atazanavir: 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.
