Objective: The authors conducted a dose-finding study of D-cycloserine, a partial agonist at the glycine site of the N-methyl-D-aspartate subtype of the glutamate receptor, added to conventional neuroleptics for schizophrenic patients with prominent negative symptoms.
Method: Nine patients with schizophrenia completed consecutive 2-week trials of placebo and four doses of D-cycloserine. Clinical assessments were videotaped and were scored by a rater who was blind to temporal sequence.
Results: D-Cycloserine at a dose of 50 mg/day produced a significant reduction (mean = 21%, SD = 28%) in negative symptoms and significantly improved reaction time as measured by Sternberg's Item Recognition Paradigm, a test mediated in part by prefrontal cortex.
Conclusions: This preliminary evidence suggests that D-cycloserine may improve negative symptoms and cognitive deficits over a narrow dose range when added to conventional antipsychotic agents.