MDR-1 genotypes and quetiapine pharmacokinetics in healthy volunteers.

Background: P-glycoprotein is an efflux transporter encoded by the multidrug-resistance MDR-1 gene, which influences the absorption and excretion of a variety of drugs. The relation between quetiapine pharmacokinetics and MDR-1 genetic polymorphisms remains controversial. Therefore, the aim of the present study was to analyze the association between quetiapine plasma concentrations and MDR-1 genetic polymorphisms in a bioequivalence trial.

Methods: Quetiapine bioequivalence was studied in 24 unrelated healthy Caucasian adults with an open-label, randomized, cross-over, two-sequence and two-period design. Subjects were genotyped for 3435C>T and 1236C>T single-nucleotide polymorphisms. A linear mixed model was performed to compare pharmacokinetic parameters.

Results: Subjects with 3435T/T genotype vs. C carriers showed a higher area under the concentration-time curve from 0 to 36 h (p=0.01). Subjects classified according to 1236C>T SNP and haplotypes showed no statistically significant differences.

Conclusions: These results suggest that the polymorphic MDR-1, in particular the 3435C>T allelic variant, might influence plasma levels of quetiapine.