Factors associated with duloxetine treatment among patients with major depressive disorder in Veterans Health Administration: a retrospective study

Objective: To examine the predictors of duloxetine monotherapy versus other antidepressants among patients with major depressive disorder (MDD) in the Veterans Health Administration (VHA). Methods: Patients initiating duloxetine or other antidepressants between October 1, 2005 and October 1, 2007 were extracted from the Veterans Integrated Service Network (VISN) 16 data warehouse. All patients included had at least one MDD diagnosis prior to the initiation of duloxetine or other antidepressants. Patients with prior diabetes, schizophrenia, or bipolar disorder diagnosis were excluded. Logistic regression was used to identify predictors of duloxetine initiation versus other antidepressants. Results: Among 448 duloxetine and 11,629 non-duloxetine patients identified, more duloxetine-treated patients had pre-index opioid use (62.72% vs. 22.03%), substance abuse (36.38% vs. 27.72%), or reported pain (60.94% vs. 46.29%) than non-duloxetine treated patients (all p-values <0.001). Prior users of long-acting (odds ratio [OR] = 8.98, 95% confidence interval [CI]: 6.95, 11.60) and short-acting (OR = 3.32, 95% CI: 2.60, 4.23) opioids were more likely to initiate duloxetine than those not. Patients who experienced moderate or severe pain or substance abuse were also more likely to initiate duloxetine (OR = 1.43, 95% CI: 1.07, 1.90; 1.50, 95% CI: 1.16, 1.92; 1.41, 95% CI: 1.14, 1.75; respectively). Other significant predictors included being female, white, having non-VHA insurance, prior hospitalization, emergency room visits, dyslipidemia and hypertension (all p-values <0.05). Key Limitations: It is a retrospective analysis among VHA patients of a single VISN. Conclusion: Among the VHA patients with MDD, prior opioid use was the strongest predictor of duloxetine initiation, followed by moderate-to-severe pain and substance abuse diagnosis.