Prescribing mirtazapine with SSRIs or SNRIs for treatment-resistant depression is no more effective than placebo, a study has suggested.
Researchers said that GPs should stop the ‘growing practice’ of adding mirtazapine to SSRIs or SNRIs, as it is may cause more adverse effects.
The study looked at just under 500 patients from UK general practices who had been taking an SSRI or SNRI for depression but remained symptomatic after six weeks.
Around half of the patients were assigned to receive mirtazapine in addition to their SSRI or SNRI and half were assigned to receive a placebo.
At 12 weeks’ follow up, all patients had reduced levels of depression, measured using the Beck Depression Inventory score, with the mirtazapine group scoring 18.0 and the placebo group scoring 19.7, down from an initial score of 31.5 and 30.6 respectively.
The difference in scores was not statistically significant however, and the researchers described mirtazapine as ‘unlikely’ to have clinical benefit. They found that the differences became even smaller at 24 and 52 weeks’ follow up.
They noted that more patients who were taking mirtazapine reported more non-serious adverse effects than those were taking the placebo, with 46 patients who reported adverse effects stopping mirtazapine at 12 weeks, compared to nine stopping the placebo.
The researchers said in the paper: ‘These findings challenge the growing practice of the addition of mirtazapine to SSRI or SNRI in this group of patients
‘The lack of clear evidence of benefit in our study, combined with the increased burden of adverse effects in the mirtazapine group, means that we cannot recommend this combination as a routine strategy in primary care for those who remain depressed after adequate treatment with SSRI or SNRI antidepressants.’