Minocycline flops against treatment-resistant depression

The use of minocycline as add-on to antidepressant treatment in patients with treatment-resistant depression is safe but falls short of efficacy thresholds relative to placebo, as shown in a study.

A total of 173 adult patients were randomized to receive adjunct minocycline at 200 mg (n=84) or placebo (n=89) daily for 6 weeks with a follow-up of 6 months. All patients had a diagnosis of major depressive disorder with symptoms on the Hamilton Depression Rating Scale (HAMD-17), body mass index 18–40 kg/m², Clinical Global Impression Scale (CGI-S) score ≥4, failure to adequately respond to an initial antidepressant standard medication, and stable medication for at least 2 weeks.

Of the patients, 168 were included in the intention-to-treat population. Their mean age was 46.1 years, and the mean Montgomery-Åsberg Depression Rating Scale (MADRS) score at baseline was 26.5; 53 percent were men, and 94.6 percent were White.

Minocycline failed to attenuate the severity of depressive symptoms, with the primary endpoint of change in MADRS score from baseline to week 6 being similar between the active and placebo groups (difference, 1.46, 95 percent confidence interval [CI], −1.04 to 3.96; p=0.25).

Likewise, there was no significant difference noted in the rates of treatment completion, which were 83.3 percent in the minocycline group and 83.1 percent in the placebo group.

The findings of the present study underscore the unmet need for therapeutic approaches and predictive biomarkers in treatment-resistant depression.