D-cycloserine addition to exposure sessions in the treatment of patients with obsessive-compulsive disorder

Background Preliminary studies have shown that the addition of the partial NMDA-agonist D-cycloserine (DCS) might be promising in enhancing the results of exposure therapy in obsessive-compulsive disorder (OCD). We examined the effect of DCS addition to exposure therapy in a somewhat larger sample of OCD patients with special attention to subgroups, because of the heterogeneity of OCD. Methods A randomized, double-blind, placebo controlled trial was conducted in 39 patients with OCD. Patients received 6 guided exposure sessions, once a week. One hour before each session 125 mg DCS or placebo was administered. Results Scores on the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) declined more in the DCS group than in the placebo group, but the difference did not reach statistical significance (P = 0.076, partial η² = 0.13). Response percentages also did not differ between the DCS and the placebo group (37% and 15% respectively). In the ‘cleaning/contamination’ subgroup a significant effect was found in favour of DCS (P = 0.033, partial η² = 0.297). Conclusions The results of this study did not support the application of DCS to exposure therapy in OCD. Some specific aspects need further investigation: efficacy of DCS in a larger ‘cleaning/contamination’ (sub-)group, DCS addition only after successful sessions, interaction with antidepressants.