Cimetidine and ranitidine: comparison of effects on hepatic drug metabolism.

Abstract

Summary and conclusionsPaired studies of hepatic microsomal function were conducted in eight subjects during treatment with two histamine H2 antagonists, cimetidine and ranitidine. Cimetidine but not ranitidine inhibited the metabolism of antipyrine (phenazone) and demethylation of aminopyrine (aminophenazone) as measured by breath 14CO2 production after intravenous injection of 14C-aminopyrine.These results suggest that the metabolic inhibitory actions on the liver may be separated from H2 antagonist effects, and that ranitidine has an advantage over cimetidine by not inhibiting microsomal drug oxidative function.Introduction When drugs such as warfarin, antipyrine (phenazone), and diazepam are taken with cimetidine their metabolism is retarded.1 2 This interaction has been attributed to the

Omeprazole: effects on oxidative drug metabolism.

“…We recorded no change in liver enzyme levels with 60 mg of omeprazole so reduced drug metabolism at that dose cannot be attributed to hepatotoxicity. Overall the effects were small and less than we experienced with antisecretory doses of the histamine H2-receptor antagonist cimetidine (Henry et al, 1980). One subject who had recieved the higher dose of omeprazole without ill effect developed a rash and biochemical evidence of hepatocellular damage at the end of treatment with 30 mg/day.…”

“…Although there is some controversy (Spahn et al, 1983;Jack et al, 1983), it is widely held that drugs such as ranitidine and tiotidine, which do not possess an imidazole group, are less likely than cimetidine to produce important interactions at therapeutic doses (Henry et al, 1980;Serlin et al, 1981;Staiger et al, 1981).…”

“…This was performed using methods previously described (Henry et al, 1979(Henry et al, , 1980 Results (Tables 1 and 2) Omeprazole 30 mg/day…”

Ranitidine and cimetidine; drug interactions with single dose and steady‐state nifedipine administration.

“…It is well established that cimetidine inhibits liver enzymes involved in drug metabolism (Henry et al, 1980;Puurunen et al, 1980;Borm et al, 1981;Rollinghoff & Paumgartner, 1982;Ruffalo & Thompson, 1982). This may sometimes be clinically important.…”

Lack of interaction between ranitidine and phenytoin [letter]

“…Ranitidine, a newer histamine H2-receptor antagonist, has a different chemical structure from cimetidine; the imidazole ring of cimetidine has been replaced by a furan ring and the side chain has been modified. Ranitidine does not impair the metabolism of antipyrine (Henry et al, 1980), warfarin (Serlin et al, 1981) or propranolol (Heagarty et al, 1982). We therefore compared the effect of ranitidine and cimetidine on steady state plasma phenytoin levels in epileptic patients.…”