New approaches to the treatment of refractory depression

Although the majority of patients with depression respond well to their initial pharmacologic treatment, as many as 30% to 45% fail to achieve an adequate response. In addition to the more traditional lithium and thyroid hormone augmentation strategies, a number of new pharmacotherapeutic approaches are currently being used to help manage refractory depression, including the addition of another agent or a switch to another antidepressant. Augmentation and switching strategies are often selected in order to obtain a different neurochemical effect (e.g., adding a relatively noradrenergic agent to a relatively serotonergic antidepressant). In particular, several studies have suggested that depressed patients refractory to treatment with selective serotonin reuptake inhibitors (SSRIs) may show a good response to newer agents that have a pharmacologic profile distinct from the SSRIs. Furthermore, preliminary studies have shown that the addition of SSRIs to either noradrenergic drugs such as the tricyclic antidepressants (TCAs) or dopaminergic agents may be efficacious, even though concerns about drug-drug interactions and tricyclic cardiac toxicity have limited the use of TCA-SSRI combinations. The introduction of reboxetine, a relatively selective norepinephrine reuptake inhibitor, may increase the use of the latter therapeutic approach because of its improved safety profile compared with the TCAs. The review of treatment options for refractory depression that follows will outline the advantages, disadvantages, and level of support for a number of new treatment strategies.