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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, RESULTS. Meshes: Adolescent, Adult, Alleles, Cohort Studies, Cytochrome P-450 CYP3A, Dose-Response Relationship, Drug, Female, Gene Expression Regulation, Genotype, Humans, Infant, Newborn, Nifedipine, Obstetric Labor, Premature, Pharmacogenetics, Polymorphism, Genetic, Pregnancy, Pregnancy Outcome, Prospective Studies, Statistics, Nonparametric, Tocolytic Agents, Young Adult.
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Are nifedipine pharmacokinetics influenced by CYP3A5 genotype when used as a preterm labor tocolytic? Context: To characterize the pharmacokinetics and pharmacogenetics of nifedipine in pregnancy. Pregnant women receiving oral nifedipine underwent steady-state pharmacokinetic testing over one dosing interval. DNA was obtained and genotyped for cytochrome P450 (CYP) 3A5 and CYP3A4*1B. Nifedipine and oxidized nifedipine concentrations were measured in plasma, and pharmacokinetic parameters were compared between those women who expressed a CYP3A5*1 allele and those who expressed only variant CYP3A5 alleles (*3,*6, or *7). Fourteen women had complete data to analyze. Four women (29%) expressed variant CYP3A5; three of these women were also CYP3A4*1B allele carriers. The mean half-life of nifedipine was 1.68 ± 1.56 hours. The area under the curve from 0 to 6 hours for the women receiving nifedipine every 6 hours was 207 ± 138 µg·h /L. Oral clearance was different between high expressers and low expressers (232.0 ± 37.8 µg/mL versus 85.6 ± 45.0 µg/mL, respectively; p = 0.007).
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CYP3A5 genotype influences the oral clearance of nifedipine in pregnant women. Final Decision: yes