Aim: To examine how the endogenous CYP3A4 phenotype and CYP3A5*3 genotype of Chinese renal transplant recipients influenced the dose-corrected trough concentration (C 0 /D) and weight-corrected daily dose (D/W) of tacrolimus. Methods: A total of 101 medically stable kidney transplant recipients were enrolled, and their blood and urine samples were gathered. The endogenous CYP3A4 phenotype was assessed by the ratio of 6β-hydroxycortisol and 6β-hydroxycortisone to cortisol and cortisone in urine. CYP3A5*3 genotype was determined using PCR-RELP. Results: In overall renal transplant recipients, a multiple regression analysis including the endogenous CYP3A4 phenotype, CYP3A5*3 genotype and post-operative period accounted for 60.1% of the variability in C 0 /D ratio; a regression equation consisting of the endogenous CYP3A4 phenotype, post-operative period, body mass index, CYP3A5*3 genotype, gender, total bilirubin and age explained 61.0% of the variability in D/W ratio. In CYP3A5*3/*3 subjects, a combination of the endogenous CYP3A4 phenotype, postoperative period and age was responsible for 65.3% of the variability in C 0 /D ratio; a predictive equation including the endogenous CYP3A4 phenotype, post-operative period, body mass index, gender and age explained 61.2% of the variability in the D/W ratio. Base on desired target range of tacrolimus trough concentrations, individual daily dosage regimen was calculated, and all the observed daily doses were within the predicted range. Conclusion: This study provides the equations to predict tacrolimus metabolism and dosage requirements based on the endogenous CYP3A4 phenotype, CYP3A5*3 genotype and other non-genetic variables.

Unfortunately, this assay has a narrow linear range, and is not sensitive enough for the analysis of full plasma UA concentration-time profiles after intravenous uricase. Herein, we developed an LC-MS method with excellent sensitivity, high specificity, simple preparation procedures and a short analytical time, which was efficient for analyzing plasma samples at different sampling times after the intravenous infusion of uricase. The efficacy of a new uricase product for injection that was prepared by Escherichia coli has for the first time been investigated in humans. Experimental MaterialsUric acid was purchased from Sigma-Aldrich (St. Louis, MO). . R. ChinaA liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of uric acid in human plasma was developed and validated. Separation was achieved on a C18 column by the mobile phase of 30% water (containing 0.5% formic acid) and 70% methanol. Quantification was done using a multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 169.1 → m/z 141.1 for uric acid and m/z 171 → m/z 143 for 1,3-15 N uric acid (IS) at a positive ionization mode. The calibration curve was established over the range of 0.4096 -100 mg/L, and the correlation coefficient was better than 0.99. The intra-day and inter-day relative standard deviations were less than 5.1%. The accuracy determined at three concentrations ranged between 92.7 and 102.3%. This method was successfully applied to an efficacy study of intravenous recombinant urate oxidase produced by Escherichia coli in a clinical phase I study.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of cinacalcet in human plasma was developed and validated. This assay was based on liquid-liquid extraction and cinacalcet-d4 was used as an internal standard (IS). Separation was achieved on a C 18 column by the mobile phase A of water (containing 0.1% formic acid) and the mobile phase B of acetonitrile-water (95:5, v/v) (containing 0.2% formic acid) with gradient elution. Quantification was done using multiple reaction monitoring mode to monitor the precursor-to-product ion transitions of m/z 358.2 → m/z 155.2 for cinacalcet and m/z 362.3 → m/z 155.0 for IS at positive ionization mode. The calibration curve was established over the range 0.05-20.0 ng/mL and the correlation coefficient was >0.99. The intra-and inter-day relative standard deviations were <5.8%. Accuracy determined at four concentrations ranged between 96.0 and 106.0%. This method was successfully applied to a pharmacokinetic description of oral dose of cinacalcet and the significant effect of food intake on the pharmacokinetics of cinacalcet was first demonstrated in Chinese healthy volunteers.

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