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Objective: To determine whether single-nucleotide polymorphisms (SNPs) in candidate genes are associated with response to olanzapine-fluoxetine combination., Method: A post hoc analysis of a priori-selected SNPs used data from a clinical trial (dates: April 2002-July 2005) of olanzapine-fluoxetine combination, fluoxetine, and olanzapine in patients with major depressive disorder (DSM-IV criteria) and with nonresponse to prestudy antidepressant treatment and nonresponse to fluoxetine treatment during the study. Patients received open-label treatment with fluoxetine for 8 weeks (2 weeks, 25 mg/d; then 6 weeks, 50 mg/d), at the end of which nonresponders (< 25% decline in the 17-item Hamilton Depression Rating Scale score) were randomized to receive double-blind, monotherapy treatment with olanzapine-fluoxetine combination (6/50-18/50 mg/d, n = 71), fluoxetine (50 mg/d, n = 78), or olanzapine (6-18 mg/d, n = 56) for 8 weeks. Statistical significance was assessed at P < .05. The primary efficacy measure for within-study treatment was improvement on the Montgomery-Asberg Depression Rating Scale (MADRS)., Results: Rs36024, an intronic SNP in the norepinephrine transporter (SLC6A2), as well as 3 SNPs in melanocortin 3 receptor (MC3R) and 2 SNPs in tryptophan hydroxylase 2 (TPH2), were associated with MADRS-defined response to treatment with olanzapine-fluoxetine combination (adjusted Li-Nyholt P < .05). Except for 1 SNP in TPH2, identified SNPs were not significantly associated with response to continued-fluoxetine or olanzapine treatments., Conclusions: Our findings further support the hypothesis that the synergistic effect of olanzapine and fluoxetine on prefrontal cortical levels of norepinephrine and dopamine might be an underlying mechanism for the efficacy of olanzapine-fluoxetine combination in the treatment of treatment-resistant depression and, if replicated, may form a basis on which response to olanzapine-fluoxetine combination versus continued fluoxetine can be predicted based on variants in SLC6A2., Trial Registration: Parent study registered at ClinicalTrials.gov identifier: NCT00035321., (© Copyright 2012 Physicians Postgraduate Press, Inc.)

Objective: To evaluate common genetic variations for association with symptomatic improvement in bipolar I depression following treatment with olanzapine/fluoxetine combination (OFC) or lamotrigine., Method: Symptom improvement was assessed in 88 OFC-treated and 85 lamotrigine-treated white patients with bipolar I depression in the 7-week acute period of a randomized, double-blind study comparing OFC (6/25, 6/50, 12/25, or 12/50 mg/d [olanzapine/fluoxetine]) with lamotrigine (titrated to 200 mg/d). The original study was conducted from November 2003 to August 2004. Single nucleotide polymorphisms (SNPs) were genotyped in a set of 19 candidate genes corresponding to known sites of activity for olanzapine and fluoxetine or previously associated with antidepressant or antipsychotic response. Primary outcome was the reduction in Montgomery-Asberg Depression Rating Scale (MADRS) total score as assessed by the difference by genotype from baseline to week 7 from a mixed-effects repeated measures analysis with terms for visit, genotype, genotype-by-visit interaction, and baseline MADRS score as a covariate., Results: SNPs within the dopamine D(3) receptor and histamine H(1) receptor (HRH1) genes were significantly associated with response to OFC. SNPs within the dopamine D(2) receptor, HRH1, dopamine beta-hydroxylase, glucocorticoid receptor, and melanocortin 2 receptor genes were significantly associated with response to lamotrigine., Conclusions: SNPs in specific candidate genes were associated with symptomatic improvement in a treatment-specific fashion. These results suggest the importance of dopaminergic effects in the treatment of patients with bipolar I depression and the potential utility of genotyping in selection of pharmacologic treatments for bipolar depression., (©Copyright 2010 Physicians Postgraduate Press, Inc.)

In patients from two clinical trials, we investigated the associations of single nucleotide polymorphisms (SNPs) in candidate genes with prolactin level changes during treatment with olanzapine/fluoxetine combination. In both cohorts, three dopamine receptor D2 (DRD2) SNPs were associated with prolactin changes. DRD2 may influence susceptibility to hyperprolactinemia associated with antipsychotic treatment.