CYP2C9 is one of four known members of the human cytochrome P450 CYP2C superfamily, with at least 57 CYP2C9 alleles being previously identified. Genetic polymorphisms of CYP2C9 significantly influence the efficacy and safety of some drugs, which might cause adverse effects and therapeutic failure. The purpose of the present study was to clarify the role of 36 CYP2C9 alleles, 21 novel alleles (*36-*56) found in the Chinese population, in the oxidative metabolism of diclofenac in vitro. Insect microsomes expressing the 36 human CYP2C9 alleles were incubated with 2-100 μM diclofenac for 30 min at 37 degrees C and terminated by the addition of 30 μL 0.1 M HCl. Diclofenac and 4'-hydroxyl (OH)-diclofenac, the major diclofenac metabolite, were analyzed by high-performance liquid chromatography (HPLC). Compared with wild-type CYP2C9*1, most variants showed significantly altered values in V(max), K(m) and intrinsic clearance (V(max)/K(m)). Only one variant exhibited markedly increased intrinsic clearance value, whereas 31 variants exhibited significantly decreased values. Thus, this study demonstrated that more attention should be given to subjects carrying these CYP2C9 alleles when administering diclofena.

A simple, specific and sensitive HPLC method has been developed for the determination of metoprolol and its two metabolites in human plasma and urine. Separation of metoprolol, alpha-hydroxymetoprolol, O-desmethylmetoprolol and esmolol (internal standard) was achieved on an Agilent XDB-C18 column (150 mm x 4.6 mm, 5 mu m) using fluorescence detection with Ex 216 nm and Em 312 nm. The mobile phase consisted of ACN-H2O-0.1%TFA. The analysis was performed in less than 16 min with a flow rate of 0.8 mL/min. The assay was linear over the concentration range of 5-600 ng/mL and 2.5-300 ng/mL for metoprolol and its metabolites, respectively. The LOQ were 5.0 and 2.5 ng/mL for plasma and urine, respectively. Good precision and accuracy for metoprolol and its two metabolites were obtained. The extraction recoveries were found to be more than 86.91% both in plasma and urine. At the same time, the method was successfully applied to nine healthy volunteers who had been given an oral tablet of 100 mg metoprolol. Crown Copyright (c) 2013 Published by Elsevier B.V. All rights reserved.