Effects of cimetidine and ranitidine on hepatic drug metabolism.
Cimetidine has been shown to impair elimination of a number of drugs metabolized by the hepatic mixed-function oxidase enzymes. It is uncertain whether this is related to its histamine H2-receptor antagonism or to its intrinsic structure. Ranitidine is a more potent H2-receptor antagonist and has a completely different structure. Cimetidine (1 gm/day for 7 days) induced a 23% and 35% fall in mean systemic clearance of antipyrine and theophylline, whereas ranitidine (300 mg/day 7 days) had no significant effect on the clearance of either drug. Our data suggest that the inhibition of drug metabolism by cimetidine is not related to histamine H2-receptor antagonism.
D000328:Adult; D000983:Antipyrine / Q000097:blood / Q000378:metabolism; D002927:Cimetidine / Q000494:pharmacology*; D004347:Drug Interactions; D005260:Female; D005663:Furans / Q000494:pharmacology*; D006146:Guanidines / Q000494:pharmacology*; D006207:Half-Life; D006635:Histamine H2 Antagonists / Q000494:pharmacology*; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D006899:Mixed Function Oxygenases / Q000378:metabolism; D011899:Ranitidine; D013806:Theophylline / Q000097:blood / Q000378:metabolism
D005663:Furans; D006146:Guanidines; D006635:Histamine H2 Antagonists; D002927:Cimetidine; D011899:Ranitidine; D013806:Theophylline; D006899:Mixed Function Oxygenases; D000983:Antipyrine