Agomelatine as adjunctive therapy with SSRIs or SNRIs for major depressive disorder: a multicentre, double-blind, randomized, placebo-controlled trial.

Background: In general, traditional antidepressants often have limited efficacy in patients with major depressive disorder (MDD). Agomelatine, as an antidepressant with a different mechanism of action, might have adjunctive effects on traditional antidepressants. This study aimed to investigate the augmentation effect of agomelatine versus placebo in treating MDD patients who failed to respond to selective serotonin reuptake inhibitors (SSRIs) and serotonin-noradrenaline reuptake inhibitors (SNRIs).

Methods: This is an 8-week, multi-centred, double-blinded, randomized, and placebo-controlled trial. Participants diagnosed with MDD and demonstrated inadequate response to SSRI or SNRI lasting at least 2 weeks were randomly allocated to receive either agomelatine or placebo in conjunction with SSRIs or SNRIs. The 17 items of the Hamilton Depression Scale (HAMD-17) were employed to assess depression severity. The primary outcome is the total score of HAMD-17 at week 8. Secondary outcomes included HAMD-17 scores at weeks 2 and 4 and clinical remission and response over 8 weeks. Adverse events (AEs) reported in both groups were recorded. A linear mixed model was established for both primary and secondary outcomes.

Results: A total of 123 eligible participants were included, among which 60 were randomized into the agomelatine group, and 63 were randomized into the placebo group. The between-group difference in HAMD-17 score reduction from baseline to week 8 was not significant (difference = - 0.12, 95% CI = - 3.94 to 3.70, P = 0.90; Cohen's d = 0.022). In addition, we did not observe significant differences between the two treatment groups for secondary outcomes, including response remission, and AEs.

Conclusions: This study did not obtain significant findings in favour of the augmentation effect of agomelation for MDD patients. However, agomelatine was generally well tolerated and demonstrated a favourable safety profile when used in combination with SSRIs and SNRIs.

Trial registration: This trial is registered at ClinicalTrials.gov ( https://clinicaltrials.gov ), the registration number is NCT04589143.