The metabolism of four sulphonamides in cows

Abstract

The metabolism of sulphanilamide, sulphadimidine (4,6 dimethyl 2 sulphanilamido pyrimidine), sulphamethoxazole (5 methyl 3 sulphanilamidoisoxazole) and sulphadoxine (5,6 dimethoxy 4 sulphanilamidopyrimidine) given by intravenous injection has been examined in cows. The sulphonamides were present mainly as unchanged drugs in blood samples collected 2 hr after administration. The sulphonamides were excreted in the milk partly as unchanged drugs and partly as conjugated metabolites whereas only small amounts were excreted as the N4 acetyl derivatives. The unchanged drug and the N4 acetyl derivative were the major constituents in urine samples after administration of sulphanilamide, sulphamethoxazole and sulphadoxine. Besides the unchanged drug, the N4 acetyl derivative and the conjugated metabolites, three further metabolites of sulphadimidine were isolated from urine samples and identified. They were 5 hydroxy 4,6 dimethyl 2 sulphanilamidopyrimidine, 4 hydroxymethyl 6 methyl 2 sulphanilamido pyrimidine and sulphaguanidine.