Felbamate metabolism in pediatric and adult beagle dogs.

In a metabolism study, three male and three female pediatric dogs and three male and three female adult beagle dogs received a single oral dose of 60 mg/kg [14C]felbamate. Urine and feces were collected up to 72 hr. Excreta samples were extracted with ethyl acetate and 14C metabolite profiles were generated by HPLC analysis of the extracts. The total 14C dose recoveries were 88.2% for the pediatric and 85.9% for the adult groups; recovery in urine accounted for 61.7 and 69.7%, respectively. The 14C metabolite profiles in urine and feces were similar, with three major peaks corresponding to unchanged felbamate and two hydroxylated metabolites. There was no significant sex difference in profiles within each age group. However, the sum amount of all metabolites in the urine was higher, and the amount of unchanged drug was lower in pediatric dogs. For the 0-24 hr samples, the metabolites/drug ratio in urine was 2.0-2.1 for pediatric dogs and 1.0-1.2 for adult dogs. This indicated a higher metabolic rate in the pediatric dogs.