Lack of relationship between debrisoquine oxidation phenotype and the pharmacokinetics of quinine.

The relationship between debrisoquine oxidation phenotype and the pharmacokinetics of quinine after a single dose (600 mg) of quinine sulphate was studied in eight extensive metabolizers (EM) and five poor metabolizers (PM). The mean elimination half-life of quinine in the PMs (10.2 +/- 1.6 (s.d.)h) was similar to that in the EMs (10.9 +/- 1.7 h). The oral clearance of quinine in the PM subjects was 0.092 +/- 0.021 l h-1 kg-1 and was not significantly different (P greater than 0.05) from that observed in the EM subjects (0.073 +/- 0.019 l h-1 kg-1). This suggests that even though quinine is extensively metabolized by oxidative biotransformation, this is carried out largely by P450 isoenzymes different from P450IID6 which oxidizes debrisoquine.