Implications of cyp2d6 polymorphisms for therapeutic drug monitoring in patients with hypertension

Based on genotype, 117 patients (35.3%) were intermediate-, 21 (6.3%) were poor- and 3 (0.9%) were ultra-rapid metabolizers, comparable to the European reference population. The low frequency of ultra-rapid metabolizers did not affect the classification of non-adherence. Serum concentrations of metoprolol were related to the CYP2D6 genotype. Some (perhaps 5-10%) non-adherent patients with absent or severely reduced enzyme activity may have been misclassified as adherent; with a higher serum concentration of metoprolol due to poor metabolism rather than excellent adherence.Conclusions: In 331 hypertensive patients with a normal distribution of CYP2D6 polymorphisms, the genotype seemed to influence the serum concentration of metoprolol, but did not affect the classification of non-adherence. However, perhaps 5-10% of the non-adherent patients with reduced metabolism may have been misclassified as adherent.