REVIEW OF: Mowla A et al, Int Clin Psychopharmacol 2022;38(1):4-8

STUDY TYPE: Randomized, double-blind, placebo-controlled trial

Mirtazapine is used frequently to augment antidepressants in depression and anxiety, but is this strategy effective for OCD? Mirtazapine’s serotonergic actions are complex, leading to speculation that it may cause or treat OCD (see The Carlat Psychiatry Report, October 2021). This study aimed to clarify the matter by testing mirtazapine augmentation in patients with OCD.

This 12-week, double-blind, placebo-controlled trial enrolled 61 patients from a single center in Iran, with independent funding. The patients had a primary diagnosis of OCD that did not respond to sertraline monotherapy (mean dose 250 mg/day). Mirtazapine dosing started at 7.5 mg and increased by 7.5 mg weekly until symptoms remitted or side effects limited tolerability. In the end, the mean dosage was 29.56 mg/day. The primary outcome was severity, as measured by the Yale-Brown Obsessive-Compulsive Scale (YBOCS). A secondary outcome was response rate, defined as improvement in the YBOCS score by ≥35% at week 12.

The mirtazapine and placebo groups started out with similar YBOCS scores. Four patients dropped out of each group after enrollment, leaving 22 patients in the mirtazapine group and 23 in the placebo group. The YBOCS improved significantly more in the mirtazapine group relative to the placebo group at the four-, eight-, and 12-week checkpoints. At week 12, the average YBOCS in the mirtazapine group was 11.13 ± 4.27 vs 18.94 ± 3.88 in the placebo group. Response rates also reached statistical significance at week 12, with nine responders (40.9%) in the mirtazapine group vs only one in the placebo group. 

CARLAT TAKE

With this small study, mirtazapine augmentation enters the ranks of third-line treatments for OCD. We need large, well-designed controlled trials to ­clarify mirtazapine’s role in augmenting OCD ­treatment.