WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• The interindividual variability of the pharmacokinetic parameters of cilostazol is relatively large. * Cilostazol undergoes extensive hepatic metabolism via the P450 enzymes, primarily CYP3A and, to a lesser extent, CYP2C19. * Indeed, <1% of the administered dose of cilostazol is excreted unchanged in the urine.

WHAT THIS STUDY ADDS

• A population pharmacokinetic analysis of cilostazol was conducted to evaluate the impact of CYP3A, CYP2C19 and ABCB1 polymorphisms on cilostazol disposition in vivo. * Genetic polymorphisms of CYP3A5 and CYP2C19 explain the substantial interindividual variability in the pharmacokinetics of cilostazol. * ABCB1 genotypes do not to appear to be associated with the disposition of cilostazol.

AIMS

To investigate the influence of genetic polymorphisms in the CYP3A5, CYP2C19 and ABCB1 genes on the population pharmacokinetics of cilostazol in healthy subjects.

METHODS

Subjects who participated in four separate cilostazol bioequivalence studies with the same protocols were included in this retrospective analysis. One hundred and four healthy Korean volunteers were orally administered a single 50- or 100-mg dose of cilostazol. We estimated the population pharmacokinetics of cilostazol using a nonlinear mixed effects modelling (nonmem) method and explored the possible influence of genetic polymorphisms in CYP3A (CYP3A53), CYP2C19 (CYP2C192 and CYP2C19*3) and ABCB1 (C1236T, G2677T/A and C3435T) on the population pharmacokinetics of cilostazol.

RESULTS

A two-compartment model with a first-order absorption and lag time described the cilostazol serum concentrations well. The apparent oral clearance (CL/F) was estimated to be 12.8 l h(-1). The volumes of the central and the peripheral compartment were characterized as 20.5 l and 73.1 l, respectively. Intercompartmental clearance was estimated at 5.6 l h(-1). Absorption rate constant was estimated at 0.24 h(-1) and lag time was predicted at 0.57 h. The genetic polymorphisms of CYP3A5 had a significant (P < 0.001) influence on the CL/F of cilostazol. When CYP2C19 was evaluated, a significant difference (P < 0.01) was observed among the three genotypes (extensive metabolizers, intermediate metabolizers and poor metabolizers) for the CL/F. In addition, a combination of CYP3A5 and CYP2C19 genotypes was found to be associated with a significant difference (P < 0.005) in the CL/F. When including these genotypes, the interindividual variability of the CL/F was reduced from 34.1% in the base model to 27.3% in the final model. However, no significant differences between the ABCB1 genotypes and cilostazol pharmacokinetic parameters were observed.

CONCLUSIONS

The results of the present study indicate that CYP3A5 and CYP2C19 polymorphisms explain the substantial interindividual variability that occurs in the metabolism of cilostazol.