Rapid and simple method for the analysis of nateglinide in human plasma using HPLC analysis with UV detection

Nateglinide (NA) is a novel oral mealtime glucose regulator, recently approved for the treatment of type II diabetes mellitus. To facilitate clinical studies investigating the dependence of NA elimination on the genotype of cytochrome P450 isoenzymes, we developed a rapid HPLC method for determination of NA in human plasma samples. The validated limit of quantitation (LOQ) of 0.1 microg/ml is low enough to allow determination of pharmacokinetic parameters of the substance. The intra-assay coefficients of variation (CV) ranged from 1.6 to 12.9% at NA concentrations of 0.5-7.5 microg/ml. The inter-assay variation for the same plasma concentrations ranged from 3.8 to 8.4%. The calibration was linear in the range of 0.1-20 microg/ml. For the quantitation of NA, only 50 microl of plasma were needed. Following protein precipitation in human plasma, the samples were separated by isocratic reversed phase HLPC and analyzed using ultraviolet detection at 210 nm. Sample preparation time and analysis time are both short and allow rapid analysis of large sample sets.