Randomized, proof-of-concept trial of low dose naltrexone for patients with breakthrough symptoms of major depressive disorder on antidepressants

•Low-dose naltrexone is thought to function via a dopaminergic mechanism that may have potential antidepressant effects.•In 12 depressed subjects who relapsed on pro-dopaminergic antidepressants, low dose naltrexone reduced depression severity.•Low-dose naltrexone augmentation may be effective for depressive relapse, but the findings must be interpreted with caution.

BackgroundGiven the proposed dopaminergic mechanism of low-dose naltrexone (LDN), we examined its efficacy as augmentation for depressive breakthrough on pro-dopaminergic antidepressant regimens.Methods12 adults (67% female, mean age = 45±12) with recurrent DSM-IV major depressive disorder (MDD) on dopaminergic antidepressant regimens (stimulants, dopamine agonists, bupropion [≥300 mg/day], aripiprazole [≤2.5 mg/day], or sertraline [≥150 mg/day]) were randomized to naltrexone 1 mg b.i.d. (n=6) or placebo (n=6) augmentation for 3 weeks.ResultsAll subjects completed the trial. Hamilton Depression Rating Scale (HAM-D-17) scores (primary outcome measure) decreased from 21.2±2.0 to 11.7±7.7 for LDN, from 23.7±2.3 to 17.8±5.9 for placebo (Cohen's d=0.62; p=0.3 between treatment groups). HAM-D-28 scores decreased from 26.2±4.0 to 12.0±9.8 for LDN, from 26.3±2.6 to 19.8±6.6 for placebo (d=1.15; p=0.097). Montgomery-Asberg Depression Rating Scale (MADRS-10 item) scores decreased from 30.4±4.9 to 12.2±8.4 for LDN, from 30.7±4.3 to 22.8±8.5) for placebo (d=1.45; p=0.035). MADRS-15 item scores decreased from 36.6±6.2 to 13.2±8.8 for LDN, from 36.7±4.2 to 26.0±10.0 for placebo (d=1.49; p=0.035). Clinical Global Improvement Scale-Severity (CGI-S) scores decreased from 4.3±0.5 to 3.0±1.1 for LDN, from 4.3±0.5 to 4.0±0.6 for placebo (d=1.22; p=0.064).LimitationsSmall study; restrictions on allowed antidepressants.ConclusionLDN augmentation showed some benefit for MDD relapse on dopaminergic agents. Confirmation in larger studies is needed.