Clinical effects of CYP2D6 phenoconversion in patients with psychosis

Sex and age effects on prevalence of CYP2C19 and CYP2D6 Phenoconversion risk over time in patients with psychosis

Pharmacogenetics in psychiatry may have benefits for medication treatment success. However, medication regimes leading to drug-drug interactions and potential phenoconversion of actionable pharmacogenetic phenotypes challenge the application of pharmacogenetics. Although polypharmacy is common, its impact in patients with psychosis is understudied, even though these patients might benefit from pharmacogenetics-guided medication adjustment. Here, we investigated the impact of two pharmacogenes relevant in psychiatric practice, CYP2C19 and CYP2D6, and the effect of sex and age. Medication use and predicted occurrence of phenoconversion was examined in a sample of patients with psychosis over a period of approximately six years. Bayesian statistics were applied to examine longitudinal effects. Our results show that women used more medications, including CYP2C19 and CYP2D6 inhibitors and (actionable) substrates. No significant sex or age differences were found for phenoconversion of either enzyme. A sex-effect on CYP2C19 inhibitor use was found but appeared to be driven by weakly inhibiting oral contraceptives, which were reported only in women. The phenoconversion rate for both enzymes appeared to change over time, suggesting that phenoconversion is a dynamic state that may affect patients differently over their lifetime. To further improve treatment in this patient population, long-term and regular updated medication monitoring in (pharmacogenetic) research as well as application in practice are recommended.

Unidentified CYP2D6 genotype does not affect pharmacological treatment for patients with first episode psychosis

BACKGROUND

Research on the pharmacogenetic influence of hepatic CYP450 enzyme 2D6 (CYP2D6) on metabolism of drugs for psychosis and associated outcome has been inconclusive. Some results suggest increased risk of adverse reactions in poor and intermediate metabolizers, while others find no relationship. However, retrospective designs may fail to account for the long-term pharmacological treatment of patients. Previous studies found that clinicians adapted risperidone dose successfully without knowledge of patient CYP2D6 phenotype.

AIM

Here, we aimed to replicate the results of those studies in a Dutch cohort of patients with psychosis (N = 418) on pharmacological treatment.

METHOD

We compared chlorpromazine-equivalent dose between CYP2D6 metabolizer phenotypes and investigated which factors were associated with dosage. This was repeated in two smaller subsets; patients prescribed pharmacogenetics-actionable drugs according to published guidelines, and risperidone-only as done previously.

RESULTS

We found no relationship between chlorpromazine-equivalent dose and phenotype in any sample (complete sample: p = 0.3, actionable-subset: p = 0.82, risperidone-only: p = 0.34). Only clozapine dose was weakly associated with CYP2D6 phenotype (p = 0.03).

CONCLUSION

Clinicians were thus not intuitively adapting dose to CYP2D6 activity in this sample, nor was CYP2D6 activity associated with prescribed dose. Although the previous studies could not be replicated, this study may provide support for existing and future pharmacogenetic research.