Mirtazapine added to SSRIs or SNRIs for treatment resistant depression in primary care

The Phase III MIR study evaluated mirtazapine in combination with one of two kinds of antidepressants in the setting of treatment-resistant depression.

The Phase III MIR study evaluated mirtazapine in combination with one of two kinds of antidepressants in the setting of treatment-resistant depression. The trial was conducted at more than 100 primary care practices in the United Kingdom and involved nearly 500 adult participants who previously had not responded to monotherapy with a serotonin-noradrenaline reuptake inhibitor (SNRI) or selective serotonin reuptake inhibitor (SSRI). Patients continued to take their prescribed SNRI or SSRI, but 214 of them were randomized to add mirtazapine to their regimen with the remaining 239 randomized to placebo. The primary outcome was Beck depression inventory II score at 12-week followup, at which time results from 431 patients in the starting study sample were included. The scores were lower for the mirtazapine patients, meaning they had fewer depressive symptoms, but they were also more likely experience adverse effects and terminate treatment. Based on those findings, the investigators do not see a clinically meaningful incentive to supplement SSRI or SNRI with mirtazapine in patients with treatment-resistant depression, whose need for additional treatment options continues to go unmet.