Partial response and nonresponse to antidepressant therapy: current approaches and treatment options

Response to antidepressant drug therapy is less than optimal for a considerable proportion of depressed patients; at present, however, few data exist to guide their rational therapeutic management. This review describes general principles for the management of such patients. This review is the result of an expert roundtable meeting convened to review published clinical data and clinical experience and provide clinicians with evidence-based principles on the management of patients who fail to respond optimally to initial antidepressant therapy.

Failure to respond may be defined as a < 25% decrease on an accepted symptom rating scale such as the Montgomery-Asberg Depression Rating Scale (MADRS) or the Hamilton Rating Scale for Depression (HAM-D) in a patient who has received an adequate dosage for 4 weeks. In these patients, a neuropharmacologic rationale exists to switch to an agent with a different mode of action or a dual action. Partial response may be defined as 6 to 8 weeks at an adequate dosage and 25% to 50% decrease in MADRS or HAM-D score. In these patients, dose escalation should be considered, followed by augmentation and switching strategies. For augmentation, knowledge of neuropharmacology may allow prediction of which second agent will potentiate or complement the action of the first agent; it may also permit the prediction of potential safety concerns.

On the basis of a review of the medical literature and clinical experience regarding patients with partial response or nonresponse to antidepressant drug therapy, it appears that simultaneous targeting of both the noradrenergic and serotonergic systems is one of the most effective augmentation strategies. Switching to an agent of a different class is probably optimal for those patients who fail to respond to first-line therapy.