Influences of Organic Cation Transporter Polymorphisms on the Population Pharmacokinetics of Metformin in Healthy Subjects

This study investigated the effects of genetic polymorphisms in organic cation transporter (OCT) genes, such as OCT1-3, OCTN1, MATE1, and MATE2-K, on metformin pharmacokinetics. Of particular interest was the influence of genetic polymorphisms as covariates on the variability in the population pharmacokinetics (PPK) of metformin using nonlinear mixed effects modeling (NONMEM). In a retrospective data analysis, data on subjects from five independent metformin bioequivalence studies that used the same protocol were assembled and compared with 96 healthy control subjects who were administered a single oral 500 mg dose of metformin. Genetic polymorphisms of OCT2-808 G > T and OCTN1-917C > T had a significant (P < 0.05) effect on metformin pharmacokinetics, yielding a higher peak concentration with a larger area under the serum time-concentration curve. The values obtained were 102 +/- 34.5 L/h for apparent oral clearance (CL/F), 447 +/- 214 L for volume of distribution (V (d)/F), and 3.1 +/- 0.9 h for terminal half-life (mean +/- SD) by non-compartmental analysis. The NONMEM method gives similar results. The metformin serum levels were obtained by setting the one-compartment model to a first-order absorption and lag time. In the PPK model, the effects of OCT2-808 G > T and OCTN1-917C > T variants on the CL/F were significant (P < 0.001 and P < 0.05, respectively). Thus, genetic variants of OCTN1-917C > T, along with OCT2-808 G > T genetic polymorphisms, could be useful in titrating the optimal metformin dose.