Memantine Augmentation of Antidepressants

\- Objective The objective of this study is to evaluate the efficacy and safety of 20 mg of memantine administered once daily as an augmentation agent for subjects who have been taking antidepressants for at least 1 month but who have experienced an incomplete or absent therapeutic response. \- Background Memantine is a moderate affinity, uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist that is approved for the treatment of moderate-to-severe dementia of the Alzheimer's type. It has been commercially available in 23 countries worldwide since 1982. There are reports in the published literature that suggest NMDA receptors may be involved in the etiology of depressive disorders. The NMDA antagonist ketamine has been shown to have antidepressant effects in a placebo-controlled clinical trial (Berman et al., 2000). Uncompetitive NMDA receptor antagonists, including memantine, have been shown to exhibit antidepressant-like activity in animal models of depression (Moryl et al., 1993, Papp and Moryl 1994). Animal studies also support the possibility that uncompetitive NMDA receptor antagonists may work synergistically in combination with antidepressants in animal models of depression (Rogoz et al., 2001). Some authors have hypothesized a role for NMDA receptors in the therapeutic effects of numerous antidepressants (Skolnick et al., 1996). \- Study Design and Duration This is a randomized, single site, double-blind, placebo-controlled, parallel-group study in outpatients. The study consists of an 8-week double-blind treatment period. Approximately 25 patients will be randomized to each treatment group (memantine or placebo) for a total of approximately 50 patients.