Disposition of quinine in plasma after a single oral and intramuscular dose in healthy adult Africans.

The pharmacokinetics of quinine were assessed in healthy adult Africans after a single oral dose of 500 mg quinine base (n = 11) and after a single intramuscular injection of 500 mg quinine base (n = 7). Quinine was assayed in plasma by high performance liquid chromatographic method (HPLC). Quinine was rapidly absorbed reaching a mean peak concentrations of 2.9 (sd 0.5) and 4.5 (1.3) mg L-1 respectively in a median time of 3.0 (range 2.0-4.0) and 1.5 (range 0.5 4.0) h respectively after oral and intramuscular administration. The peak concentration (Cmax) was significantly higher after intramuscular than after oral administration [Cmax = 4.5 (1.3) versus 2.9 (0.5) mg L-1, p < 0.01]. The mean half-life [t1/2z = 11.7 (2.9) versus 10.7 (3.5) h, P > 0.2] respectively, volume of distribution (Vz = 2.5 (0.7) versus 2.2 (0.99) L Kg-1, P > 0.2) respectively and estimated plasma clearance [CLp = 0.15 (0.04) versus 0.15 (0.09) L h-1 Kg-1, P > 0.2] respectively were not significantly different after oral and intramuscular administration. The mean AUCo-oo was higher after intramuscular than after oral administration [71.8 (29.4) versus 54.9 (19.2) mg.h.L, P > 0.1] respectively but this was not significant. The pharmacokinetic parameters after intramuscular dose were similar to those obtained in seven healthy subjects given quinine by slow intravenous infections over four hours. The dose was well tolerated.