SIMULTANEOUS DETERMINATION OF PLASMA PHENYTOIN AND ITS PRIMARY HYDROXYLATED METABOLITES IN CARBON TETRACHLORIDE-INTOXICATED RATS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

We have developed a simple and sensitive method for the simultaneous d etermination of phenytoin (PHT), 5-(p-hydroxyphenyl)-5-phenylhydantoin (P-HPPH) and 5-(m-hydroxyphenyl)-5-phenylhydantoin (m-HPPH) in rat pl asma by high-performance liquid chromatography. The three substances w ere separated on a reversed-phase column (5 mu m TSK gel ODS-80TM, 250 mm x 4.6 mm I.D.) using acetonitrile-0.008 M NaH2PO4 (pH 6) (35:65, v /v) as a mobile phase at a flow-rate of 0.8 ml/min. Absorbance was mon itored at 215 nm. The quantification limit was 50 ng/ml for each of PH T, m-HPPH and p-HPPH. The mean recoveries for DPH, m-HPPH and p-HPPH f rom plasma were 95.6 +/- 3.6, 94.5 +/- 4.2 and 98.6 +/- 2.9%, respecti vely.