CYP2D6 genotypes in revolving door patients with bipolar disorders: A case series

RATIONALE: In psychiatric disorders, interindividual differences in cytochrome P450 (CYP)2D6 (CYP2D6) enzymatic activity could be responsible of adverse drug reactions (ADRs) and therapeutic failures (TFs) for CYP2D6-metabolized drugs, contributing to the periodical hospital readmissions of the revolving door (RD) condition. PATIENT CONCERNS: We investigated CYP2D6 genotypes in a controlled series of 5 consecutive RD patients with Bipolar Disorder (BD). DIAGNOSES: Psychiatric patients affected by Bipolar Disorder. INTERVENTIONS: We defined TFs as a difference at the Brief Psychiatric Rating Scale score ΔBPRS < 25% at each 1-week of stable treatment, and ADRs as the onset of extrapyramidal symptoms and/or metabolic impairment with weight gain. OUTCOMES: At 3 months, a mean number of 2.75 ± 1.26 ADR and a mean ΔBPRS score of 16.07 ± 0.05% were observed. At 6 months of follow-up, compared to the only patient without BD (ΔBPRS < 32.10%), BD patients (n = 4) showed TFs (ΔBPRS < 25%). CYP2D6 genotyping revealed intermediate metabolizer phenotypes for BD patients and an extensive metabolizer phenotype for the patient without BD. In BD patients, the ratio of drugs maintained/discontinued for TFs or ADRs was 1.75 for non-CYP2D6 versus 0.33 for CYP2D6 interacting drugs, while the proportion of ADR:TF was 0:4 versus 6:3. LESSONS: Our findings may suggest that CYP2D6 clinically relevant genotypes may be involved in the unwanted outcomes observed in RD patients with BD.