Abstract: Objective To establish a method for the determination of phenytoin sodium in serum to assist rational administration in clinic. Methods Serum samples were extracted with solid phase extraction（SPE），and phenytoin sodium was detected with high performance liquid chromatography（HPLC）. The separation was performed on a Venusil C¹⁸ column with a mobile phase of methanol∶water（50∶50） at a flow rate of 0. 8 mL/min. The eluent was monitored at 230 nm. Results The method showed a good specificity between analyte and matrix. A good linearity of phenytoin sodium was observed over the concentration range of 2. 84-181. 80 μg/mL with correlation coefficient of 0. 999 4. The limits of detection（LOD）was 0. 6 μg/mL. The mean recovery of phenytoin sodium in quality control（QC） samples at concentrations of 2. 84，22. 70，181. 80μg/mL were between 92. 7%-96. 2%，intra-and inter- day precision RSD were both less than 10%（ n =5 ）. Conclusion The proposed method is specific，accurate and sensitive. The results indicate that the method is satisfactorily applied to detect the serum phenytoin sodium concentrations，and to perform related pharmacokinetics studies.

Key words: phenytoin sodium, serum drug concentration, pharmacokinetics, solid phase extraction（SPE）, high performance liquid chromatography（HPLC）