ABSTRACT
Nateglinide (NAT) and Pioglitazone (PIO) are an antidiabetic drugs combination and currently under clinical trial in countries like Japan. In this study, an alternative, a simple, sensitive high-performance liquid chromatography method has been developed (limit of detection: 15 ng/mL and limit of quantification: 50 ng/mL) for simultaneous estimation of this drug combination in rat plasma. Most remarkably, bioavailability of NAT has been increased markedly on coadministration with PIO, than when it was administered alone. Thus, PIO is assumed to retard the catabolism of NAT by inhibiting metabolic liver-microsomal enzyme, especially CYP2C9. Using a Waters Nova-Pak C 18 column (150 × 3.9 mm, 4 µm) and a mobile phase of acetonitrile: 10 mM KH2PO4 (60: 40, V/V (volume by volume)) pH 3.5, the analysis was performed at 210 nm with a flow rate of 1.5 mL/min. In silico docking via molecular dynamics simulation revealed that NAT-CYP2C9 binding affinity may be reduced after PIO attachment, presumably due to the binding site overlapping of the two drugs. Thus, it has been proposed that NAT and PIO may be an efficient synergistic fixed dose combination against diabetes mellitus, and the above method can foster a simple but highly sensitive bioanalytical estimation for routine analysis.