Five potential therapeutic agents as antidepressants: a brief review and future directions.

Despite the availability of numerous antidepressants, many patients with depression do not show adequate response. The therapeutic lag between drug administration and onset of clinical improvement observed with conventional antidepressants has led to a need for antidepressants with a novel mechanism of action. Recently, five such agents, including acetyl-L-carnitine, scopolamine, ω-3 polyunsaturated fatty acids, ketamine, and selective 5-HT7 serotonin receptor antagonists, have gained interest as potential antidepressants with enhanced symptom control, improved tolerability, and faster onset of action compared to conventional antidepressants. This review provides an update and critical examination of these five novel therapeutic agents as potential antidepressants.