Quantification of midazolam/1′-hydroxymidazolam and their pharmacokinetic characteristics in rat brain by microdialysis combined with LC-MS n / 中国药理学通报

ABSTRACT

Aim To develop a sensitive, rapid and ac-curate LC-MSn method for determination of midazolam/1′-hydroxymidazolam and their pharmacokinetic char-acteristics in rat brain. Methods SD rats received in-travenous injection of midazolam ( 5 mg · kg-1 ) via femoral vein, a probe drug of cytochrome P450 3A. The microdialysis ( MD ) samples in situ brain were collected every 8 mins at 2. 0μl·min-1 in 2. 4 hours. Analytes in brain dialysate were quantified by the pro-posed LC-MSn method. Gradient elution was performed on an Agilent Eclipse Plus-C18 column ( 2 . 1 × 50 mm, 3. 5 μm). The mobile phase consisted of 2 mmol ·L-1 ammonium acetate and acetonitrile. The analyte was detected using electrospray ionization ( ESI ) in multiple reaction monitoring ( MRM) modes. The reac-tion selected ions were 326 . 1/291 . 1 m/z for midazo-lam, 342. 1/324. 1 m/z for 1′-hydroxymidazolam and 285. 1/154. 0 m/z for diazepam as internal standard. Result The linear ranges of midazolam and 1′-hydroxymidazolam were 0 . 78~100 and 0 . 195 ~12 . 5μg·L-1 respectively. The lower limit of quantification was 0 . 2 μg · L-1 . The RSD of intra- and inter-batch precisions was less than 7 %. The RSD of accuracy was from -1 . 34 to -8 %. Conclusion This sensi-tive and rapid LC-MSn method is suitable for determi-nation of midazolam/1′-hydroxymidazolam in rat brain dialysate. MD combined with LC-MSn method may give assistance to deep and further studies of drug metabo-lism and CYP3A enzyme in brain.