REPRODUCIBILITY OVER TIME OF MEPHENYTOIN AND DEBRISOQUINE HYDROXYLATION PHENOTYPES

Mephenytoin and debrisoquine hydroxylation phenotypes were determined twice in 15 Spanish healthy volunteers with an interval of about one y ear. The phenotype assignment did not change in any subject for either debrisoquine or mephenytoin. Among extensive metabolisers of mephenyt oin, there was a slight increase (P = 0.04) of the mephenytoin-S/R ena ntiomeric ratio over the study period. The family members of a poor me taboliser of mephenytoin were phenotyped, and the heterozygous extensi ve metabolisers were found to have higher mephenytoin-S/R ratios than other extensive metabolisers suggesting a correlation between the geno type and the S/R ratio.