The effects of rabeprazole on metformin pharmacokinetics and pharmacodynamics in Chinese healthy volunteers

The aim was to investigate the role of rabeprazole on the pharmacokinetics (PK) and pharmacodynamics (PD) of metformin. The in vitro inhibition assays on metformin transport were carried out and showed that the half maximal inhibitory concentration (IC50) of rabeprazole on OCT2-mediated metformin transport was 26.0 μM, whereas the IC50 on MATE1-mediated metformin transport inhibition was 4.6 μM. Fifteen healthy Chinese male volunteers were enrolled and given two different doses of metformin plus the co-administration of placebo or rabeprazole. Plasma concentrations of metformin were measured up to 12 h after the second dose. The glucose-lowering effects and the variation of insulin concentrations were evaluated during the oral glucose tolerance test (OGTT). The AUC0-12 of metformin plus rabeprazole were 28,276 ± 5187 ng/ml·h, which was significantly higher than AUC0-12 of metformin plus placebo (24,691 ± 3129 ng/ml·h). Thus, rabeprazole can modestly influence the PK of metformin, suggesting the precaution of using the two drugs together. In OGTTs, rabeprazole decreased the values of AUCinsulin and the maximum insulin concentration. Although rabeprazole showed inhibition effect on OCT2-mediated metformin transport, the glucose-lowering effect of metformin remained the same regardless of its PK changes. Further studies are needed to warrant the effect of rabeprazole on metformin.