A placebo-controlled crossover trial of D-cycloserine added to clozapine in patients with schizophrenia.

Author(s): Goff DC, Henderson DC, Evins AE, Amico E

Affiliation(s): Psychotic Disorders Program of the Massachusetts General Hospital, Boston, USA.

Publication date & source: 1999-02-15, Biol Psychiatry., 45(4):512-4.

Publication type: Clinical Trial; Controlled Clinical Trial; Randomized Controlled Trial

BACKGROUND: D-Cycloserine, a partial agonist at the glycine recognition site of the NMDA receptor, has previously been shown to improve negative symptoms when added to conventional antipsychotics and, in one preliminary dose-finding study, worsened negative symptoms when added to clozapine. METHODS: Seventeen schizophrenia outpatients treated with clozapine were assigned in random order to 6-week trials of D-cycloserine 50 mg/day and placebo in a crossover design separated by a 1 week placebo washout. RESULTS: Eleven patients competed the 13-week study. D-Cycloserine significantly worsened ratings of negative symptoms compared to placebo but did not significantly affect ratings of psychotic symptoms. CONCLUSIONS: The differing effects of D-cycloserine on negative symptoms when added to clozapine compared to conventional antipsychotics suggests that activation of the glycine recognition site may play a role in clozapine's efficacy for negative symptoms.