Supplementing standard obsessive-compulsive disorder (OCD) medication with glutamatergic medication such as gabapentin and memantine has no additional positive effect in patients with OCD, according to research published in the Journal of Psychiatric Research.

To determine whether adjunctive gabapentin or memantine and standard treatment with a selective serotonin-reuptake inhibitor (SSRI) might lead to further improvements in patients with OCD researchers conducted a double-blind placebo-controlled trial in which 99 outpatients with OCD (average age 29.59) were randomly assigned to receive one of three treatments for 8 weeks: fluoxetine plus gabapentin, fluoxetine plus memantine, or fluoxetine plus placebo.

Researchers used the Yale-Brown Obsessive Compulsive Scale to rate patients’ OCD symptoms at baseline, 4 weeks, and trial completion. To be included in the study, participants were required to have a baseline score of ≥15 points. Mean scores at baseline differed significantly between groups: 18.70 for gabapentin, 16.36 for placebo, and 16.39 for memantine.

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Neither the gabapentin nor the memantine group demonstrated significant score change over time. The placebo group was actually found to have a superior Time X Group interaction, with an overall average reduction of 4.24 points. In comparison, gabapentin dropped 4.03 points and memantine dropped 3.15 points (P =.042).

There were no significant differences between the groups in response rates from baseline to 4 and 8 weeks. Adverse events in the memantine group tended toward rash; in the placebo group toward anxiety; and in the gabapentin group toward drowsiness, anxiety, and drowsiness plus anxiety.

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The researchers reported several study limitations, including the risk for unknown confounding factors inherent in outpatient treatment such as family issues and job strains.

“The key finding of the present study was that neither adjuvant gabapentin nor adjuvant memantine had better effects on symptoms of OCD than a placebo,” said the researchers. “The present pattern of results therefore adds to the current literature on the treatment of this disorder in that adjuvant memantine and adjuvant gabapentin does not appear to be justified.”


Farnia V, Gharehbaghi H, Alikhani M, et al. Efficacy and tolerability of adjunctive gabapentin and memantine in obsessive compulsive disorder: double-blind, randomized, placebo-controlled trial [published online July 21, 2018]. J Psychiatr Res. doi:10.1016/j.jpsychires.2018.07.008