Placebo-controlled trial of D-cycloserine added to conventional neuroleptics, olanzapine, or risperidone in schizophrenia

Objective: The authors investigated the clinical effects of D-cycloserine when added to treatment with conventional neuroleptics, olanzapine, or risperidone for treatment-resistant schizophrenia. Method: Twenty-four patients participated in a double-blind, placebo-controlled, 6-week crossover trial with D-cycloserine, 50 mg/day, added to their fixed dose of antipsychotic medication. Clinical ratings were performed every 2 weeks. Results: D-cycloserine treatment was well tolerated and resulted in a significant reduction in negative symptoms (mean= 15%). The degree of improvement did not differ between patients treated with conventional neuroleptics and those treated with olanzapine or risperidone. Conclusions: These data support the efficacy of the addition of 50 mg/day of D-cycloserine to treatment with conventional neurolepties and suggest that therapeutic benefits may also be attained when D-cycloserine is added to olanzapine or risperidone.