Metabolism of Clindamycin I: Absorption and Excretion of Clindamycin in Rat and Dog

Abstract

Clindamycin hydrochloride, randomly labeled with tritium, was synthesized and used for animal metabolism studies. The drug was administered to rats (oral and intraperitoneal routes) and dogs (oral and intramuscular routes) at a dose of 50-150 mg./kg. In both species, after the oral or parenteral drug administration, the excretion of radioactive materials in the urine (approximately one-third of the dose) and in the feces (approximately two-thirds of the dose) was independent of the route of administration. The initial rate of excretion for the oral dose was significantly faster than the parenteral dose. In the dog, peak plasma radioactivity concentrations were observed at 2 and 4hr. after oral and intramuscular administration, respectively. The slower rate of absorption and excretion following parenteral compared to oral administration was believed due to precipitation of the drug at the injection site or a difference in transport processes. Based upon the identical areas under the plasma total radioactivity versus time curves, plus the fact that the distribution of radioactivity excreted in urine and feces was independent of the route of administration, it was concluded that after oral administration the absorption of this drug into the bloodstream was almost complete and that little appeared to pass through the GI tract for direct elimination.