The urinary metabolic profile of metyrapone in the rat. Identification of two novel isomeric metyrapol N-oxide metabolites.
This study was designed to fully characterize the urinary metabolic profile of metyrapone following a 50 mg/kg ip dose to male Sprague-Dawley rats. Preliminary examination of alkaline dichloromethane extracts of urine by TLC and HPLC showed the absence of the intact drug, but the presence of moderate amounts of the two isomeric metyrapone mono-N-oxides, together with small amounts of metyrapol and the alpha-pyridone metabolite. These compounds have previously been reported as in vitro metabolites. Large amounts of two new metabolites of metyrapone were also observed and were conclusively identified as the isomeric metyrapol N-oxides by a combination of low- and high-resolution mass spectrometry. Quantitation by HPLC showed that metyrapol and the two metyrapone mono-N-oxides accounted for 4 and 10% of the dose, respectively. The two metyrapol mono-N-oxides accounted for more than 75% of the dose. These are novel metabolites not previously reported either as in vivo or in vitro metabolites.
Department of Pharmacy, University of Manchester, United Kingdom.
J I
JI
Usansky
L A
LA
Damani
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D007536:Isomerism; D008297:Male; D013058:Mass Spectrometry; D008657:Metabolic Clearance Rate; D008797:Metyrapone / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000652:urine; D051381:Rats; D011919:Rats, Inbred Strains
C002196:metyrapol; C020775:metyrapone N-oxide; D008797:Metyrapone