High Sustained Success Rate With Adjunctive Memantine (Namenda) in Treatment-Resistant Bipolar Disorder
Koukopoulos et al. published a study of the anti-Alzheimer’s drug memantine in the Journal of Affective Disorders in 2012. The study of memantine (10-30mg/day) as an add-on to patients’ regular treatment for highly treatment-resistant bipolar disorder was open (i.e. not blind, randomized or placebo-controlled), but it deserves careful attention for its noteworthy results. Of the 40 patients in the study, who had been severely ill for long periods of time, 72.5% showed a rating of much or very much improved on the Clinical Global Impressions Scale for Bipolar Disorders (CGI-BP) after both 6 months and 12 months. Among rapid cyclers, 68.4% stabilized and remitted on memantine.
Editor’s Note: Memantine is an antagonist of glutamate NMDA receptors and is approved by the Federal Drug Administration (FDA) for the treatment of Alzheimer’s dementia, but not for other indications. Nonetheless, few (if any) drugs have this high a response rate in such a difficult-to-treat population, and the researchers suggest that even based on these preliminary data (which replicate their previous observations), careful clinical trials of memantine in individual patients would be worthy of consideration.
The data are so promising that fast-track development of this drug for FDA approval would be warranted. More formal randomized controlled clinical trials are needed.
We have written before about a few treatments that have rapid-onset antidepressant effects, including intravenous (IV) ketamine (at a dose of 0.5mg over 40 minutes). Ketamine works by blocking glutamate NMDA receptors, but the rapid antidepressant effects it produces (within 2 hours of treatment) last only 3 to 4 days. Given the similar mechanisms of action of ketamine and memantine and memantine’s high success rate in this study by Koukopoulos, it is plausible that treatment with memantine could extend the rapid onset effects of IV ketamine. However, this speculation has not yet been tested. At the very least, the similarity between the mechanisms of memantine and ketamine in blocking the glutamate NMDA receptor lends additional support to the clinical rationale for treating bipolar disorder with adjunctive memantine.