N-oxidation and N-demethylation of methylephedrine by rat-liver microsomes.
1. The metabolism of methylephedrine was studied using rat-liver microsomes; methylephedrine N-oxide and ephedrine were isolated as metabolites. 2. The formation of methylephedrine N-oxide was inhibited by methimazole or by preincubation of microsomes, but that of ephedrine was not; whereas the formation of ephedrine was inhibited by either SKF 525-A or CO, but the formation of the N-oxide was not. 3. Pretreatment of rats with phenobarbital increased N-demethylation, but decreased N-oxidation. Pretreatment with 3-methylcholanthrene did not influence either reaction. 4. The results indicate that the formation of the N-oxide was mediated by the flavin-containing monooygenase system and that of ephedrine was mediated by the cytochrome P-450 system.
Inoue
T
T
National Research Institute of Police Science, Tokyo, Japan.
Tanaka
K
K
D000818:Animals; D065607:Cytochrome P-450 Enzyme Inhibitors; D004809:Ephedrine / Q000031:analogs & derivatives* / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D008713:Methimazole / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D065607:Cytochrome P-450 Enzyme Inhibitors; D011725:Pyridines; C013109:metapyrone; D008713:Methimazole; C041707:N-methylephedrine; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D004809:Ephedrine