Abstract

The excretion kinetics of carboxytolbutamide after the oral ingestion of sodium tolbutamide of tolbutamide or tolbutamide free acid, intravenous injection of carboxytolbutamide and intravenous injection of sodium tolbutamide were studied in normal adult humans. Tolbutamide is nearly quantitatively oxidized in vivo to carboxytolbutamide and carboxytolbutamide is quantitatively excreted in urine. The oxidation of tolbutamide and excretion of the carboxytolbutamide formed follows the kinetics of consecutive first order processes. The mean half-life for the in vivo oxidation of tolbutamide was found to be 5.70 hours with a range of 4.4 to 6.85 hours in 14 tests with 4 subjects. The mean half-life for excretion of carboxytolbutamide was found to be 0.49 hour with a range of 0.38 to 0.56 hour in 3 tests with 3 subjects, meaning that on the average this metabolite is removed from the body about 12 times more rapidly than it is formed.