NMDA Antagonists in Bipolar Depression

Bipolar disorder affects 2% of the population in the United States and the depressive phase contributes disproportionally to morbidity and mortality. At present, few approved treatments for bipolar depression are available, and have primarily depended on manipulations of brain monoaminergic systems. In contrast, recent studies suggest that the N-methyl-D-aspartate glutamate-receptor (NMDAR) antagonist, ketamine, may provide near-immediate relief for treatment resistant depression. Its utility during long-term treatment, however, is limited by its psychotomimetic potency and the need for repeated IV infusions. D-cycloserine (DCS) is an approved oral antibiotic for tuberculosis drug and a well-studied mixed agonist/antagonist at the NMDAR/glycine binding site. DCS showed preliminary evidence of efficacy in a pilot study. DCS would thus be practical from both a safety and route of administration perspective. The present study will explore the feasibility and safety of DCS for maintenance treatments, as measured by magnetic resonance spectroscopy (MRS).