Abstract: AIM: To establish a HPLC method by solid-phase extraction which was used for determining tol-butamide and its metabolites in human plasma and urine, and to study its pharmacokinetics. METHODS; The concentrations of tolbutamide and its metabolites in human plasma and urine by solid-phase extraction were deter-mined by HPLC. Watere Spherisorb 5 μm Phenyl column (4.6 mm×250 mm) was used as the analytical column and the mobile phase was consisted by methanol-0.02 mmol·L^-1 pH 3.3 Na₂Ac buffer(28:72). The flow rate was 1 ml·min^-1 and UV detection wavelength was 230 nm. The concentrations of tolbutamide and its metabolites in plasma and urine in healthy volunteers were determined by HPLC and the pharmacokinetic parameters were ana-lyzed by 3p97. RESULTS: The linear range was 2-100 μmol·L^-1 (r=0.999) for tolbutamide in human plasma by solid phase extraction. The recovery was 105.1%-103.9%. The linear range was 2-50 μmol·L^-1 (r=0.999) for carboxytolbutamide in human urine. The recovery was 98.8%-100.1%. The linear range was 1-50 μmol·L^-1 (r=0.999) for 4-hydroxytolbutamide in human urine. The recovery was 95.4%-103.5%. The linear range was 1-50 μmol·L^-1 (r=0.999) for tolbu-tamide in human urine. The recovery was 97.7%-106.6%. The within-day and between-day derivations of all samples were less than 15%. A single oral dose of 500 mg tolbutamide was administrated to the volunteers, the main pharmacokinetic parameters AUC_0-∞, t_1/2, T_max, C_max, and MR_0-24 were 2644.6±472.8 μmol·h^-1·L^-1, 1.4±0.6 h,235.8±47.3 μmol·L^-1 and 277.5±125.6, respectively. CONCLUSION: The method is simple and accurate, and it can be used determining tolbutamide and its metab-olites in biological samples. Tolbutamide is mainly excret-ed through urine in form of carboxytolbutamide and hydroxytolbutamide.

Key words: solid phase extraction, HPLC, tolbu-tamide, pharmacokinetics