TISSUE CONCENTRATIONS OF CLINDAMYCIN AFTER MULTIPLE ORAL DOSES IN NORMAL CATS

Brown, S.A., Zaya, M.J., Dieringer, T.M., Hunter, R.P., Nappier, J.L., Hoffman, G.A., Hornish, R.E. & Yein, F.S. Tissue concentrations of clindamycin after multiple oral doses in normal cats. J. vet. Pharmacol. Therap. 13, 270–277. Eighteen normal cats were randomly allocated into two blocks with three treatment groups and dosed orally with clindamycin aqueous solution for 10 days at a dosage rate of 5.5 mg/kg twice daily (Group 1), 11 mg/kg twice daily (Group 2), or 22 mg/kg once daily (Group 3). At the end of dosing, all cats were killed and tissues were taken for clindamycin concentration analysis. Clindamycin was extracted from tissues using solid‐phase extraction columns followed by microbiological assay of clindamycin using a cylinder plate assay using M. luteus. Recovery from each tissue was determined by inoculating known concentrations of clindamycin into drug‐naive tissues and comparing the observed concentration from the expected concentration. Confirmation that the bioassay detected clindamycin and not N‐desmethylclindamycin, its active metabolite, was done using gas‐chromatography‐mass‐spectrometry. Concentrations were highest in the lung, with tissue: serum ratios greater than 3 in all groups. Concentrations were higher in Group 3 than Group 1 (P< 0.05). Only liver concentrations in Group 3 were statistically higher than in Group 2, although all tissues except bone marrow and CSF had numerically higher concentrations in Group 3 than Group 2. The tissuerserum ratio was < 1 in all tissues studied except bone, cerebrospinal fluid, brain, and skeletal muscle. Dr Scott Anthony Brown, Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine, Texas A<M University, College Station, TX 77843, USA. Copyright © 1990, Wiley Blackwell. All rights reserved