Study of the metabolism of phenothiazines: determination of N-demethylated phenothiazines in urine.

When phenothiazine drugs (chlorpromazine, promazine, promethazine, propiomazine, propionylpromazine, trifluoperazine and trimeprazine) were reacted with m-chloroperbenzoic acid, N-demethylated phenothiazines were obtained in moderate yield. The mass spectra of the N-demethylated phenothiazines showed either m/z 44 and 72 or m/z 58 as characteristic ions depending on their side chain. The N-demethylated propiomazine was identified as a metabolite of propiomazine from the urine of a rat which was given propiomazine orally.