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Clin Pharmacol Ther. 2014 Mar;95(3):321-30. doi: 10.1038/clpt.2013.193. Epub 2013 Sep 30.

An investigation of CYP2D6 genotype and response to metoprolol CR/XL during dose titration in patients with heart failure: a MERIT-HF substudy.

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School of Medicine, University of Leeds, Leeds, UK.
Division of Epidemiology, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, UK.
Wallenberg Laboratory for Cardiovascular Research, Sahlgrenska Academy, Gothenburg University, Gothenburg, Sweden.
Department of Cardiology, University Medical Centre Groningen, University of Groningen, Groningen, The Netherlands.
Department of Cardiology, Rikshospitalet, University of Oslo, Oslo, Norway.


To explore the pharmacogenetic effects of the cytochrome P450 (CYP)2D6 genotype in patients with systolic heart failure treated using controlled/extended-release (CR/XL) metoprolol, this study assessed the CYP2D6 locus for the nonfunctional *4 allele (1846G>A; rs3892097) in the Metoprolol CR/XL Randomised Intervention Trial in Congestive Heart Failure (MERIT-HF; n = 605). Participants were characterized as extensive, intermediate, or poor metabolizers (EMs, IMs, or PMs, respectively), based on the presence of the CYP2D6*4 allele (EM: *1*1, 60.4%; IM: *1*4, 35.8%; and PM: *4*4, 3.8%). Plasma metoprolol concentrations were 2.1-/4.6-fold greater in the IM/PM groups as compared with the EM group (P < 0.0001). Metoprolol induced significantly lower heart rates and diastolic blood pressures during early titration, indicating a CYP2D6*4 allele dose-response effect (P < 0.05). These effects were not observed at maximal dose, suggesting a saturable effect. Genotype did not adversely affect surrogate treatment efficacy. CYP2D6 genotype modulates metoprolol pharmacokinetics/pharmacodynamics during early titration; however, the MERIT-HF-defined titration schedule remains recommended for all patients, regardless of genotype.

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