The pharmacokinetics of primaquine in calves after subcutaneous and intravenous administration

Abstract

The pharmacokinetics of primaquine was studied in calves of 180–300 kg live weight. Primaquine was injected at 0.29 mg/kg (0.51 mg/kg as primaquine diphosphate) intravenously (IV) or subcutaneously (SC) and the plasma concentrations of primaquine and its metabolite carboxyprimaquine were determined by high-performance liquid chromatography. The extrapolated concentration of primaquine at zero time after IV administration was 0.50±0.48 µg/ml (mean ±SD) which decreased with an elimination half-life of 0.16±0.07 h. Primaquine was rapidly converted to carboxyprimaquine after either route of administration. The peak concentration of carboxyprimaquine was 0.50±0.08 µg/ml at 1.67±0.15 h after IV administration. The corresponding value was 0.47±0.07 µg/ml at 5.05±1.20 h after SC administration. The elimination half-lives of carboxyprimaquine after IV and SC administration were 15.06±0.99 and 12.26±3.06 h, respectively. The areas under the concentration-time curve for carboxyprimaquine were similar following either IV or SC administration of primaquine; the values were 11.85±2.62 µg.h/ml after the former and 10.95±2.65 µg.h/ml after the latter. The mean area under the concentration-time curve for primaquine was less than 0.1 µg.h/ml after either route of administration.