Placebo-controlled trial of glycine added to clozapine in schizophrenia

Objective: The purpose of this study was to evaluate the effects of high-do se oral glycine on positive and negative symptoms and cognitive function wh en added to clozapine in adults with schizophrenia. Method: The authors conducted a double-blind, placebo-controlled, parallel- group trial of 60 g/day of glycine added to clozapine for 8 weeks in 30 adu lts with schizophrenia. Clinical ratings were performed every 2 weeks. Results: Twenty-seven patients completed the trial. Glycine augmentation of clozapine produced no statistically significant change in positive or nega tive symptoms or cognitive functioning. No subjects showed clinically signi ficant worsening of clinical ratings. Conclusions: These data, combined with data from previous trials with D-cyc loserine and glycine, suggest that agonists at the glycine site may be less effective when combined with clozapine than they are when combined with co nventional antipsychotics.