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Background
The selective serotonin reuptake inhibitors (SSRIs) have become a mainstay of treatment for depression, despite the fact that they have certain limitations, including the development of some specific adverse events, such as gastrointestinal complaints (e.g. nausea, anorexia and diarrhoea) and neuropsychiatric complaints (e.g. insomnia and nervousness).[1] In addition, between 30% and 60% of SSRI-treated patients may experience some form of treatment-induced sexual dysfunction, which is increasingly recognized as having an important impact on quality of life.[2]
Mirtazapine has a unique and specific effect on both the noradrenergic and serotonergic neurotransmitter systems in the CNS, being an antagonist of α2-adrenergic autoreceptors and heteroreceptors and an antagonist of postsynaptic serotonin 5-HT2 and 5-HT3 receptors.[3] Recent evidence from a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing the efficacy of mirtazapine with that of other classes of antidepressant showed that mirtazapine was likely to be superior to SSRIs at 2 weeks in terms of both response (risk ratio [RR] 1.36, 99% CI 1.13, 1.64; p < 0.01) and remission (RR 1.68, 99% CI 1.20, 2.36; p < 0.01), but to not differ significantly to these drugs at the end of 6-12 weeks of treatment.[4] In terms of overall acceptability, there was no statistically significant difference between mirtazapine and other antidepressants in terms of either withdrawal rates for any reason (in comparison with SSRIs, RR 1.07, 95% CI 0.92, 1.26; p = 0.38) or withdrawal due to the development of adverse events during trials (in comparison with SSRIs, RR 1.22, 95% CI 0.87, 1.73; p = 0.25), although mirtazapine was significantly inferior to sertraline for both outcomes in a sub-group analysis, presented in the same study.[4]
Given no substantial differences in the overall efficacy and acceptability of mirtazapine compared with other antidepressants, focus should be placed on other clinically relevant considerations, such as possible differences in adverse-event profiles, in order to tailor a treatment to the needs of individual patients.[5] Several previous RCTs on the efficacy of mirtazapine have shown that mirtazapine was more likely to cause dry mouth,[6] fatigue,[7] somnolence[6,8] and appetite increase or weight gain[8-11] than other antidepressants. In terms of systematic reviews or meta-analyses of adverse events of mirtazapine, to the best of our knowledge, only one meta-analysis has...