The metabolism of N-hydroxyphentermine by rat liver microsomes

N-Hydroxyphentermine is oxidized to 2-methyl-2-nitro-1-phenylpropane by rat liver microsome preparations. This oxidation accounts for differences noted in levels of N-hydroxyphentermine formed from phentermine in washed and unwashed microsome preparations. The reaction is inhibited by hemoglobin and catalase, whose presence in unwashed microsomes could terminate the N-oxidation of phentermine at the hydroxylamine level. The hydroxylamine-nitro-oxidation appears to be dependent on cytochrome P-450, as the reaction was induced by phenobarbital pretreatment and inhibited by carbon monoxide and 2,4-dichloro-6-phenylphenoxyethylamine.