Specific serotonin and noradrenaline reuptake inhibitors (SNRIs). A review of their pharmacology, clinical efficacy and tolerability

Considerable progress has been made in improving the tolerability of antidepressant drugs. The classical tricyclic antidepressants (TCA) are still, however, the standard for efficacy. The selective serotonin reuptake inhibitors are better tolerated that the tricyclics, but their efficacy in major depression is, at best, equivalent to the earlier compounds and probably inferior in certain cases. Recently a new class of antidepressants has been developed that inhibit selectively the reuptake of both serotonin and noradrenaline with no affinity for the receptors responsible for the adverse effects of the TCAs. These compounds are referred to as the specific serotonin and noradrenaline reuptake inhibitors or SNRIs. This article reviews the pharmacological and clinical characteristics of the two principal compounds of this class, milnacipran (Ixel®) and venlafaxine (Effexor®). This new class of antidepressants, as represented by these two compounds, presents an efficacy comparable to TCAs with a more benign side-effect profile. Certain trials suggest that they may have efficacy superior to SSRIs, especially in more severe depression, with a tolerability which is globally similar. This class therefore appears to offer a potential useful addition to the therapeutic arsenal of antidepressant drugs.