Acute and continuation treatment adequacy with venlafaxine extended release compared with fluoxetine

To compare treatment adequacy in the management of depression during the acute and continuation phases between patients newly treated with venlafaxine extended release (XR) and those newly treated with fluoxetine.

Retrospective observational analysis of pharmacy claims data.

Large California-based managed care organization.

A total of 11,298 patients newly prescribed venlafaxine XR or fluoxetine between January 1, 2000, and February 28, 2001, and continuously enrolled throughout the study, as well as a subset of 7430 patients who continued taking venlafaxine XR or fluoxetine during the follow-up period.

The Health Plan Employer Data and Information Set definition was used for continuous antidepressant treatment during the acute and continuation phases. Treatment adequacy was determined for those deemed continuous. Patients receiving within +/- 10% of the target dose for each drug (venlafaxine XR 75-150 mg, fluoxetine 20 mg) were defined as receiving an adequate dose. Logistic regression was used to evaluate venlafaxine XR versus fluoxetine on treatment adequacy, controlling for age, sex, physician specialty, and pharmacy benefit. The unadjusted adequacy rate for the venlafaxine XR-only group was 79% versus 57% for the fluoxetine-only group for 84 continuous days (p<0.0001) and 77% versus 52%, respectively, for 180 continuous days (p<0.0001). The adjusted odds ratios of achieving treatment adequacy with venlafaxine XR only versus that with fluoxetine only were 3.05 (95% confidence interval [CI] 2.65-3.52) for 84 continuous days and 3.57 (95% CI 3.00-4.24) for 180 continuous days.

Patients newly prescribed venlafaxine XR were at least 3 times more likely to achieve treatment adequacy for 84 and 180 days compared with those newly prescribed fluoxetine. Treatment adequacy as a proxy for optimal treatment may be an important factor to consider when selecting an antidepressant drug.