3-Hydroxylation of salicylamide in mice

Salicylamide is an important model compound for use in investigations concerning drug disposition. In this study the metabolic fate of salicylamide at high doses was evaluated in male mice using HPLC methodology. The concentrations of salicylamide and its metabolites were determined in urine and in blood at various times after the administration of 2 or 4 mmol kg-1 salicylamide. Salicylamide, gentisamide, and their glucuronide and sulfate conjugates were detected. 2,3-Dihydroxybenzamide, the 3-hydroxy metabolite of salicylamide, as well as its glucuronide and sulfate conjugates, were identified and quantitated for the first time by HPLC. 2,3-Dihydroxybenzamide had previously been detected only as a minor metabolite of salicylamide by paper chromatography. However, in the present study, 18% of the salicylamide metabolites appearing in urine after either dosage of salicylamide were 3-hydroxylation products. When a previously published HPLC method for salicylamide analysis was used, 2,3-dihydroxybenzamide glucuronide coeluted with salicylamide glucuronide. The possible formation of 3-hydroxy metabolites must be evaluated in any study of drug metabolism using salicylamide as a model compound.