Impact of CYP2D6 Polymorphism on Equilibrium Concentration of Fluoxetine in Patients Diagnosed With Major Depressive Disorder and Comorbid Alcohol Use Disorders

Fluoxetine is used in the treatment of patients with recurrent depressive disorder. Some of these patients do not achieve an adequate response to a treatment regimen containing fluoxetine, and many of these patients experience dose-dependent adverse drug reactions. The cytochrome P450 enzyme CYP2D6 is involved in the biotransformation of fluoxetine, the activity of which is quite dependent on the polymorphism of the gene encoding this enzyme.The objective of the study was to investigate the influence of the 1846G>A polymorphism of the CYP2D6 gene on the concentration/dose indicator of fluoxetine in patients diagnosed with major depressive disorder and comorbid alcohol use disorder.Our study included 101 patients with major depressive disorder and alcohol use disorder (average age: 41.3±14.5 y) who were treated with fluoxetine at an average dose of 26.1±8.7 mg/d. Treatment efficacy was assessed using validated psychometric scales, and the safety/tolerability of the therapy was assessed using the Udvalg for Kliniske Undersogelser Side-Effect Rating Scale. Genotyping was done using a real-time polymerase chain reaction. Therapeutic drug monitoring was performed using high-performance liquid chromatography-mass spectrometry.CYP2D6 genotyping by polymorphic marker 1846G>A (rs3892097) in the 101 patients found that there were 81 patients (80.2%) with the GG genotype ("wild-type," normal metabolism), 20 (19.8%) with the GA genotype (intermediate metabolism), and no subjects with the AA genotype (poor metabolism). Statistically significant results in treatment efficacy as evaluated by Hamilton Rating Scale for Depression scores at the end of the treatment course were found: GG 9.0 [confidence interval (CI): 6.0; 12.0] and GA 12.0 (CI: 9.5; 14.0), P=0.005. Statistically significant results were also obtained for the safety profile as measured by scores on the Udvalg for Kliniske Undersogelser Side-Effect Rating Scale: GG 3.0 (CI 2.0; 4.0) and GA 5.0 (CI: 4.0; 5.0), P<0.001. Finally, a statistically significant difference was found in concentration/dose indicators of fluoxetine in patients with the different genotypes: GG 4.831 (CI: 3.654; 6.204) and GA 7.011 (CI: 5.431; 8.252), P<0.001.The effect of the genetic polymorphism of the CYP2D6 gene on the efficacy and safety profiles of fluoxetine was demonstrated in a group of 101 patients with major depressive disorder and alcohol use disorder.