Use of effect size to determine optimal dose of duloxetine in major depressive disorder

At effective doses, patients with major depressive disorder (MDD) treated with duloxetine have been found to experience significant symptom improvement as measured by HAMD(17) total score. In addition, duloxetine-treated patients have significantly higher remission and response rates compared with placebo. The objective of this analysis is to determine the optimal dose of duloxetine in MDD.

Effect size for duloxetine 40mg, 60mg, 80mg, and 120mg per day were estimated using all 6 acute phase III clinical trials in patients with MDD. The tolerability of duloxetine 40mg, 60mg, 80mg, and 120mg were evaluated using pooled data from the 6 studies. The primary efficacy measure in all trials was the HAMD(17) total score, from which were determined the effect size for HAMD(17) change scores, response rates (50% reduction from baseline to endpoint), and remission rates (HAMD(17) total score < or =7).

A total of 1619 randomized patients were included in these studies, of which 632 were treated with placebo; 177 with duloxetine 40mg/day; 251 with 60mg/day; 363 with 80mg/day; and 196 with 120mg/day. An evaluation of increments in effect size between doses consistently showed that the most notable gain in effect size for efficacy was the 40-60mg/day dosage range. All dosages from 60 to 120mg were effective. The tolerability assessment indicated duloxetine at 40-120mg/day is well tolerated. Furthermore, the initial doses of 40-80mg/day were found to have comparable tolerability.

The effect size analyses demonstrate that duloxetine 40mg has minimum efficacy, and that duloxetine 60-120mg/day is effective in the treatment of patients with MDD. An initial dose less than 60mg/day might provide better tolerability for some patients diagnosed with MDD.