Differential efficacy of memantine for obsessive-compulsive disorder vs. generalized anxiety disorder: an open-label trial.

OBJECTIVE: A substantial proportion of patients with obsessive-compulsive disorder (OCD) and generalized anxiety disorder (GAD) do not respond to, or are intolerant of, standard treatments. Additional treatment strategies are therefore necessary. Excessive action of the excitatory neurotransmitter glutamate may play a role in the pathophysiology of OCD and possibly GAD. Memantine blocks the excitatory action of glutamate at the N-methyl- D-aspartate (NMDA) receptor under pathological conditions. The objective of this study was to compare the efficacy and safety of memantine in OCD and GAD, and to probe relative effects on OCD and anxiety symptoms.
METHOD: Ten OCD and 7 GAD subjects received 12 weeks of open-label memantine 10 mg twice daily, as either monotherapy or augmentation of their existing medication. Primary outcome measures were the Yale-Brown Obsessive Compulsive Scale ( YBOCS) for the OCD group, the Hamilton Anxiety Rating Scale (HARS) for the GAD group, and the Clinical Global Impression-Improvement Scale (CGII) for both groups.
RESULTS: The OCD group experienced a significant mean 40.6% reduction in YBOCS scores at endpoint (t = 4.75, p < 0.001). Three of 10 of OCD subjects were classified as responders, although 7 of 10 experienced a >/= 45% reduction in YBOCS scores. The GAD group experienced a mean 22.4% reduction in HARS scores (t = 3.56, p = 0.012). None of the GAD subjects were responders, and none experienced a >/= 50% reduction in HARS scores. Memantine was well tolerated, and there were no serious adverse effects.
CONCLUSIONS: These results suggest that memantine may have preferential efficacy in the treatment of OCD versus GAD. These preliminary findings warrant larger, placebo-controlled studies in OCD.