Dosing patterns for duloxetine and predictors of high-dose prescriptions in patients with major depressive disorder: analysis from a United States third-party payer perspective

Background: Major depressive disorder (MDD) is a common illness that affects ∼7% of adults in the United States each year. Duloxetine is a dual reuptake inhibitor of serotonin and norepinephrine that has demonstrated efficacy and tolerability in the treatment of MDD.

Objective: The purpose of our study was to examine dosing patterns and pretreatment predictors of high-dose duloxetine therapy for patients with MDD in the usual clinical setting.

Methods: Data were from 6132 commercially insured patients with MDD initiated on duloxetine during 2005 and 2006. Patients had no duloxetine use in the previous 6 months and had continuous enrollment in a health plan for the 12 months immediately preceding and following initiation. Dosing patterns and predictors of high-dose therapy with duloxetine were examined.

Results: Initial doses of duloxetine were <60 mg/d, 60 mg/d, 90 mg/d, and ≥120 mg/d for 32.4%, 60.9%, 3.1%, and 3.5% of patients, respectively. Maximum daily doses were <60 mg, 60 mg, 90 mg, and ≥120 mg for 16.3%, 59.3%, 11.0%, and 13.3% of patients, respectively. Patients treated with >60 mg/d for at least 2 months were older, were more likely to have been treated by a psychiatrist, had greater comorbidity, and had used more health care resources and psychotropic and pain medications in the previous year. The following factors were independently associated with doses of >60 mg/d: older age (odds ratio [OR] = 1.33-1.46); comorbid neuropathic pain (OR = 1.88); fibromyalgia (OR = 1.36); dysthymic disorder (OR = 1.24); prior injury/poisoning (OR = 1.19); physician specialty (psychiatrist, OR = 1.55); and prior use of psychostimulants (OR = 1.26), benzodiazepines (OR = 1.19), venlafaxine (OR = 1.35), or atypical antipsychotics (OR = 1.35).

Conclusions: Most of the commercially insured patients in this dataset were initiated and maintained on a duloxetine dose of 60 mg/d. Although the data are limited in their generalizability, the characteristics associated with higher dose therapy describe a complex group of patients who may require more intensive drug treatment and monitoring.