beta-Glucuronide and sulfate conjugation of scopolamine and glycopyrrolate

The metabolism of scopolamine and glycopyrrolate was studied in 11 healthy parturients undergoing cesarean section. After a single intramuscular injection of scopolamine (5 micrograms/kg, n = 7) or glycopyrrolate (6 micrograms/kg, n = 4), the concentrations of the drugs in the urine were determined up to 8-12 h using a radioreceptor assay. This assay measures scopolamine and glycopyrrolate with their possible active metabolites. The effect of beta-glucuronidase and sulfatase incubation on the drug concentrations was also studied. The concentrations of scopolamine and/or its active metabolites were on the average 7 times higher after incubation indicating that beta-glucuronide or sulfate conjugation is an important metabolic pathway for scopolamine. On the contrary, the glycopyrrolate concentrations increased only slightly between 1 and 3 hours after the drug injection. Thus, beta-glucuronide or sulfate conjugation plays only a minor part in the metabolism of glycopyrrolate.