Mirtazapine and paroxetine in major depression: A comparison of monotherapy versus their combination from treatment initiation

This double-blind study compared initial combination therapy against monotherapy using two antidepressant drugs with complementary mechanisms of action on the serotonin (5-HT) and norepinephrine (NE) systems. Sixty one adult patients with a DSM-IV diagnosis of unipolar depression were randomized to receive mirtazapine (30 mg/day), paroxetine (20 mg/day), or the combination of both drugs for 6 weeks. Response at week 4 was defined as a 30% reduction in the Montgomery-Asberg Depression Rating Scale (MADRS), and at week 6 as a 50% reduction in the MADRS. Remission was defined as a reduction in the MADRS score to 10 points or less. After 4 weeks, non-responders in the monotherapy groups had their medication dose increased by 50%. After 6 weeks, non-responders on monotherapy had the second trial drug added to their current regimen. Non-responders on combination therapy had the dosage of both drugs increased by 50%. There was a significantly greater decrease in MADRS scores in the combination group compared to the monotherapy groups at days 28, 35 and 42, with a 10 point difference separating the combination from the monotherapies at day 42. Remission rates at week 6 were 19% on mirtazapine, 26% on paroxetine, and 43% on the combination. Fifteen patients in the mirtazapine arm and 10 in the paroxetine arm who did not respond had the other drug added to their current regimen, and 5 on the combination had an increase in dose of both drugs secondary to non-response. Of these 30 patients, approximately 50% went on to achieve remission in the subsequent 2 weeks. These results indicate that the combined use of two antidepressants was well tolerated and produced a greater improvement than monotherapy.