LACK OF EFFECT OF CHLOROQUINE ON THE DEBRISOQUINE (CYP2D6) AND S-MEPHENYTOIN (CYP2C19) HYDROXYLATION PHENOTYPES

The effects of chloroquine (CHQ) on debrisoquine hydroxylase (CYP2D6) and S-mephenytoin hydroxylase (CYP2C19) were assessed in 11 black Zimb abwean and 12 white Swedish healthy volunteers. The activity of CYP2D6 was measured as the urinary debrisoquine to 4-hydroxydebrisoquine met abolic ratio and that of CYP2C19 as the urinary S- to R-mephenytoin en antiomer ratio (S/R). There were no statistically significant differen ces in either metabolic ratio as a result of prophylactic or loading d oses of CHQ. This indicates that CHQ does not inhibit CYP2D6 or CYP2C1 9 in vivo and is unlikely to compromise the metabolism of substrates f or these two enzymes. It is, therefore, also unlikely that residual CH Q in populations under study will interfere with phenotyping of either CYP2D6 or CYP2C19.