Association between CYP2D6 genotype and treatment effectiveness and safety in 99 hospitalized patients with major depressive disorder: a retrospective cohort study.

CYP2D6 variants that reduce enzyme activity (poor or intermediate metabolizers) alter antidepressant metabolism and drug exposure.

This retrospective cohort study assessed the association between CYP2D6 genotype and treatment outcomes in 99 patients hospitalized for major depressive disorder in Belgrade, Serbia. Patients were classified as poor (n = 5), intermediate (n = 21) or normal metabolizers (n = 73) and followed from admission to discharge, about four weeks. Compared with normal metabolizers, the reduction in HAM-D score was 4.3 points smaller in intermediate and 9.0 points smaller in poor metabolizers. TSES tolerability scores were 1.3 and 2.3 points higher respectively, with more frequent central nervous system and gastrointestinal effects and no difference in sexual dysfunction. The authors conclude that reduced CYP2D6 activity goes with poorer outcomes and points to the potential usefulness of genotyping in this setting.

Synthesis written by Geno'X. For the full original abstract, please refer to the source publication.

The sample is small, with only five poor metabolizers, and the retrospective design controls neither the drugs actually prescribed nor the co-medications that could drive phenoconversion. The findings align with existing recommendations but provide no decision threshold; a prospective trial comparing pre-emptive genotyping with usual care would be needed to change practice. What remains usable at the bedside is the reminder to consider CYP2D6 status when response is insufficient or tolerability poor.

Analysis by Dr Thibaut Benquey