mdr1 genotypes and quetiapine pharmacokinetics in healthy volunteers background pglycoprotein is an efflux transporter encoded by the multidrugresistance mdr1 gene which influences the absorption and excretion of a variety of drugs the relation between quetiapine pharmacokinetics and mdr1 genetic polymorphisms remains controversial therefore the aim of the present study was to analyze the association between quetiapine plasma concentrations and mdr1 genetic polymorphisms in a bioequivalence trialmethods quetiapine bioequivalence was studied in 24 unrelated healthy caucasian adults with an openlabel randomized crossover twosequence and twoperiod design subjects were genotyped for 3435ct and 1236ct singlenucleotide polymorphisms a linear mixed model was performed to compare pharmacokinetic parametersresults subjects with 3435tt genotype vs c carriers showed a higher area under the concentrationtime curve from 0 to 36 h p001 subjects classified according to 1236ct snp and haplotypes showed no statistically significant differencesconclusions these results suggest that the polymorphic mdr1 in particular the 3435ct allelic variant might influence plasma levels of quetiapine