Metabolism of 5-isopropyl-1-methyl-2-nitro-1H-imidazole. Identification of some urinary metabolites in the dog.

The metabolism of 5-isopropyl-1-methyl-2-nitro-1H-[2-14C] imidazole in dogs has been investigated after oral administration of 50 mg/kg. Three main metabolites, still containing the nitro group and accounting for about 50% of the total radiocarbon, together with a small amount of the unchanged drug, were isolated from the urine within 48 hr. The structures were determined by mass, infrared, and nuclear magnetic resonance spectroscopy. The biotransformations giving rise to the metabolites isolated involve the isopropyl chain of the molecule, either at the tertiary carbon atom or at one of the two methyl groups, or both. Thus, the metabolic behavior of this 2-nitroimidazole derivative appears to be similar to that previously demonstrated for the class of the isomeric 5-nitroimidazoles.