Effect of clozapine and adjunctive high-dose glycine in treatment-resistant schizophrenia.

Abstract

The focus of this study was the systematic evaluation of the clinical effects of glycine as an adjunct to the atypical antipsychotic clozapine in the treatment of schizophrenia. In a double-blind, placebo-controlled study, 19 patients with chronic, treatment-resistant schizophrenia who were maintained on optimal doses of clozapine (400-1200 mg/day) were administered either 30 g/day of glycine (N=9) or placebo (N=10) for 12 weeks. Clinical evaluations with the Brief Psychiatric Rating Scale, the Scale for the Assessment of Negative Symptoms, and the Simpson-Angus movement scale were completed biweekly. The use of glycine as an adjunct to clozapine was not effective in decreasing positive or negative symptoms. In contrast, the patients treated with clozapine without glycine had a 35% reduction in positive symptoms. These preliminary data suggest that glycine may interfere with the antipsychotic efficacy of atypical neuroleptics such as clozapine.