Effect of Ethanol on Pharmacokinetics of Diazepam in Rat by UPLC-MS/MS

Different degrees of diazepam and ethanol inhibit the central nervous system, ethanol can increase adverse reactions, and diazepam can cause toxicity when used in combination with its synergistic effect causing acute poisoning or death. Given the fact that ethanol consumption is so common and individual drinking habits differ so widely, we investigated the effect of ethanol on the pharmacokinetic parameters of diazepam. In our study, twelve rats were divided into two groups, diazepam group and diazepam combined ethanol group, six rats for each group. After centrifugation, the concentration of diazepam in rat plasma was analyzed with UPLC-MS/MS method. The chromatographic conditions were optimized using a C18 column (2.1 x 50 mm, 1.7 mu m), and the mobile phase was made up of water and acetonitrile (containing 0.1% formic acid) with gradient elution. The mass spectrometry conditions were electrospray ionization source and positive ion detection mode. Multiple reactions monitoring (MRM) mode was used for quantification. Calibration curves were linear over the range of 1-500 ng/mL for diazepam in rat plasma. The extract recoveries of diazepam in rat plasma were better than 78.6%. RSD of intra-day and inter-day precision were both less than 9%. The accuracy of the method was between 95.2% and 108.2%. This method was sensitive, repeatable and successfully applied to pharmacokinetic study of diazepam after oral administration in rats. Compared to the diazepam group, the pharmacokinetic parameters diazepam were altered by ethanol administration, AUC and C-max increased, CL decreased (p < 0.05). It suggested that ethanol could increase adverse reactions, and potentiate diazepam toxicity.