The pharmacokinetics of ondansetron after intravenous injection in healthy volunteers phenotyped as poor or extensive metabolisers of debrisoquine.

The pharmacokinetics of the 5-HT3 receptor antagonist ondansetron following an 8 mg i.v. dose were investigated in 12 subjects previously phenotyped with debrisoquine. Six subjects were poor metabolisers (debrisoquine metabolic ratios 29-131) and six were extensive metabolisers (debrisoquine metabolic ratios 0.45-3.4). There was no significant difference in AUC, Cmax, CL or t1/2 between the poor and extensive metabolisers. It is concluded that ondansetron clearance is not mediated exclusively by cytochrome P-450 2D6.