Gashaw Isabella, Kirchheiner Julia, Goldammer Mark, Bauer Steffen, Seidemann Julia, Zoller Konrad, Mrozikiewicz Przemyslaw M, Roots Ivar, Brockmöller Jürgen
Institute of Clinical Pharmacology, Charité University Medical Center, Humboldt University of Berlin, Berlin, Germany.
Clin Pharmacol Ther. 2003 Nov;74(5):448-57. doi: 10.1016/S0009-9236(03)00237-6.
There is significant interest in the assessment of the individual cytochrome p450 (CYP) 3A4 activity. We analyzed whether CYP3A4 messenger ribonucleic acid (mRNA) concentrations in leukocytes reflect CYP3A activity in the liver measured by alprazolam as an in vivo probe drug. We also wanted to identify whether genetically determined high CYP3A5 expression is associated with increased alprazolam clearance.
Alprazolam plasma concentrations were measured 10 hours after intake of 1 mg alprazolam. CYP3A4 mRNA concentrations in peripheral blood mononuclear cells were quantified in 96 healthy volunteers before and after 5-day treatment with 450 mg rifampin (INN, rifampicin) daily. Genetic polymorphisms in CYP2C19, CYP3A4, and CYP3A5 were analyzed by polymerase chain reaction, restriction fragment length polymorphism, and sequencing.
The median alprazolam concentration measured 10 hours after dosage was 8.1 mug/L (range, 4.5-14.6 mug/L) before and 1.7 mug/L (range, 0.3-4.1 mug/L) after rifampin treatment. Leukocyte CYP3A4 mRNA was detectable in all samples with a median of 28 molecules per 1 ng total ribonucleic acid before (range, 10-128 molecules per 1 ng total ribonucleic acid) and 50 molecules per 1 ng total ribonucleic acid after (range, 9-484 molecules per 1 ng total ribonucleic acid) rifampin treatment (P <.001). However, mRNA concentrations before and during rifampin induction were largely overlapping, and there was a poor correlation between mRNA concentrations and alprazolam 10-hour trough concentrations reflecting CYP3A4 activity (r = -0.4, P <.001). Alprazolam kinetics did not differ between genetically determined expressers of CYP3A5 (genotype CYP3A5*1/*3) compared with homozygous carriers of the splice site variant. A marginally significant dependence of alprazolam concentrations from the CYP2C19 allele *2 was found (P =.04).
CYP3A4 mRNA concentrations in blood cells were very low and did not reflect systemic drug clearance mediated by CYP3A enzymes. The CYP3A5 genetic polymorphism does not appear relevant for alprazolam kinetics.
个体细胞色素P450（CYP）3A4活性的评估备受关注。我们分析了白细胞中CYP3A4信使核糖核酸（mRNA）浓度是否反映以阿普唑仑作为体内探针药物所测得的肝脏中的CYP3A活性。我们还想确定基因决定的高CYP3A5表达是否与阿普唑仑清除率增加相关。
在摄入1 mg阿普唑仑10小时后测量其血浆浓度。在96名健康志愿者中，于每日服用450 mg利福平（国际非专利药品名称，利福平）进行5天治疗前后，对外周血单核细胞中的CYP3A4 mRNA浓度进行定量。通过聚合酶链反应、限制性片段长度多态性和测序分析CYP2C19、CYP3A4和CYP3A5的基因多态性。
给药10小时后测得的阿普唑仑浓度中位数在利福平治疗前为8.1 μg/L（范围4.5 - 14.6 μg/L），治疗后为1.7 μg/L（范围0.3 - 4.1 μg/L）。在所有样本中均可检测到白细胞CYP3A4 mRNA，利福平治疗前每1 ng总核糖核酸的中位数为28个分子（范围为每1 ng总核糖核酸10 - 128个分子），治疗后为每1 ng总核糖核酸50个分子（范围为每1 ng总核糖核酸9 - 484个分子）（P <.001）。然而，利福平诱导前和诱导期间的mRNA浓度有很大重叠，且mRNA浓度与反映CYP3A4活性的阿普唑仑10小时谷浓度之间的相关性较差（r = -0.4，P <.001）。与剪接位点变异的纯合携带者相比，基因决定的CYP3A5表达者（基因型CYP3A5*1/3）的阿普唑仑动力学无差异。发现阿普唑仑浓度与CYP2C19等位基因2有边缘性显著相关性（P =.04）。
血细胞中的CYP3A4 mRNA浓度非常低，不能反映由CYP3A酶介导的全身药物清除情况。CYP3A5基因多态性似乎与阿普唑仑动力学无关。
