title: Nilutamide inhibits mephenytoin 4-hydroxylation in untreated male rats and in human liver microsomes.
abstract: 1. The effects of nilutamide (an anti-androgen with a hydantoin moiety) on the 4-hydroxylation of mephenytoin were studied in rat liver microsomes. Nilutamide, at a concentration expected in human liver (100 microM) during prolonged administration of nilutamide, inhibited by 40% mephenytoin (0.3 mM) 4-hydroxylase activity in liver microsomes from untreated male rats, but not in microsomes from untreated female rats, or in microsomes from dexamethasone-treated male or female rats. 2. Administration to male rats of nilutamide, in doses (20 mg/kg i.p. twice daily) known to reproduce plasma concentrations observed in human therapeutics, decreased by 60% the 24 h urinary excretion of 4-hydroxymephenytoin after administration of mephenytoin (15 mg/kg oral). 3. Nilutamide (100 microM) markedly inhibited mephenytoin 4-hydroxylase activity in human liver microsomes. Inhibition kinetics were consistent with mixed inhibition. It is concluded that nilutamide inhibits mephenytoin 4-hydroxylase activity in untreated male rats and in human liver microsomes. It is suggested that inhibition is likely to occur in vivo in humans receiving therapeutic doses of nilutamide.
authors.affiliation: Unité de Recherches de Physiopathologie Hépatique (INSERM U-24), Hôpital Beaujon, Clichy, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Horsmans
authors.forename: D
authors.initials: D
authors.lastname: Lannes
authors.forename: D
authors.initials: D
authors.lastname: Larrey
authors.forename: M
authors.initials: M
authors.lastname: Tinel
authors.forename: P
authors.initials: P
authors.lastname: Letteron
authors.forename: J
authors.initials: J
authors.lastname: Loeper
authors.forename: D
authors.initials: D
authors.lastname: Pessayre
mesh_terms: D000726:Androgen Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D065731:Cytochrome P-450 CYP2C19; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D005292:Ferricyanides / Q000494:pharmacology; D006801:Humans; D006900:Hydroxylation; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D048289:Imidazolidines; D008297:Male; D008617:Mephenytoin / Q000031:analogs & derivatives / Q000378:metabolism* / Q000652:urine; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014217:Troleandomycin / Q000494:pharmacology
chemical_list: D000726:Androgen Antagonists; D065607:Cytochrome P-450 Enzyme Inhibitors; D005292:Ferricyanides; D007093:Imidazoles; D048289:Imidazolidines; C021277:nilutamide; C025687:4-hydroxymephenytoin; D003907:Dexamethasone; D003577:Cytochrome P-450 Enzyme System; D014217:Troleandomycin; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D008617:Mephenytoin; C028033:potassium ferricyanide