The purpose of this study is to compare the effects of D-cycloserine and glycine for treating
negative symptoms (such as loss of interest, loss of energy, loss of warmth, and loss of
humor) which occur between phases of positive symptoms (marked by hallucinations, delusions,
and thought confusions) in schizophrenics.
Clozapine is currently the most effective treatment for negative symptoms of schizophrenia.
Two other drugs, D-cycloserine and glycine, are being investigated as new treatments.
D-cycloserine improves negative symptoms when added to some drugs, but may worsen these
symptoms when given with clozapine. Glycine also improves negative symptoms and may still be
able to improve these symptoms when given with clozapine. This study gives either
D-cycloserine or glycine (or an inactive placebo) with clozapine to determine which is the
best combination.
Patients will be assigned to 1 of 3 groups. Group 1 will receive D-cycloserine plus
clozapine. Group 2 will receive glycine plus clozapine. Group 3 will receive an inactive
placebo plus clozapine. Patients will receive these medications for 8 weeks. Negative
symptoms of schizophrenia will be monitored through the Scale for the Assessment of Negative
Symptoms, Positive symptoms will be monitored through the Positive and Negative Syndrome
Scale, and additionally subjects will complete the Brief Psychiatric Rating Scale and the
Global Assessment Scale.
An individual may be eligible for this study if he/she is 18 to 65 years old and has been
diagnosed with schizophrenia.