Pharmacokinetics and bioequivalence of parenterally administered doramectin in cattle |
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| Authors: | M.A. NOWAKOWSKI,M.J. LYNCH,D.G. SMITH,N.B. LOGAN&dagger ,D.E. MOUZIN&dagger ,J. LUKASZEWICZ,N.I. RYAN,R.P. HUNTER,R.M. JONES |
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| Affiliation: | Pflzer Inc. Central Research Division. Groton, Connecticut 06340 USA;*Sandwich, Kent CT13 9NJ, UK;†Terre Haute, Indiana 47808, USA |
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| Abstract: | Plasma concentrations of doramectin in 40 cattle dosed by subcutaneous (sc) or intramuscular (i.m.) injection (200 μg/kg) were compared to assess the bioequivalence of the two routes of administration. Peak concentration ( C max), and areas under the concentration curve ( AUC0– ) were determined from plasma concentrations. Animals treated by the sc route showed a mean AUC0– of 457 ± 66 ng±day/mL (± SD) and a mean C max of 27.8 ± 7.9 ng/mL. Results from the i.m. treatment group showed a mean AUC 0– of 475 ± 82 ng-day/mL and a mean C max of 33.1 ± 9.0 ng/mL Absorption constants ( k a) determined by modelling were 0.542 ± 0.336 day-1after sc administration and 0.710 ± 0.357 day-1after i.m. administration. The 90% confidence limits on the difference between mean AUC 0– values for the sc and i.m. groups fell within 20% of the mean value for the subcutaneous group. C max was somewhat greater for the i.m. route. The 90% confidence limits on the difference in mean In ( T max+1) also fell within 20% of the mean sc value. Based on this analysis, bioequivalence of the sc and i.m. formulation has been established. |
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