Influence of the genetically controlled deficiency in debrisoquine hydroxylation on antipyrine metabolite formation.

The influence of the genetically controlled deficiency in debrisoquine hydroxylation on antipyrine metabolite formation was studied by giving 500 mg antipyrine to 14 extensive and 10 poor metabolizers of debrisoquine. The pharmacokinetics of antipyrine were determined on the basis of the saliva concentration time curve and the cumulative urinary excretion of 4-hydroxyantipyrine, norantipyrine, 3-hydroxymethyl-antipyrine, and 3-carboxyantipyrine was measured for 32 h following drug administration. Antipyrine elimination half-life, volume of distribution, and total clearance were almost equal for the two groups. Significant differences in the excretion of antipyrine metabolites were not observed, except for 3-hydroxymethyl-antipyrine which was excreted in poor metabolizers about 30% less than in extensive metabolizers (p less than 0.01). However, this difference only reached borderline significance (p less than 0.1) when clearance values for production of this metabolite were calculated. It is concluded that different species of the drug-oxidizing enzymes (cytochrome P-450 system) are involved in the metabolism of debrisoquine and antipyrine. Possibly the enzyme responsible for hydroxylating debrisoquine is partly involved in the formation of 3-hydroxymethyl-antipyrine.