title: A six-month, placebo-controlled trial of D-cycloserine co-administered with conventional antipsychotics in schizophrenia patients.
abstract: BACKGROUND
  D-Cycloserine, a partial agonist at the glycine site of the N-methyl-D-aspartate receptor, has demonstrated inconsistent efficacy for negative and cognitive symptoms of schizophrenia. The strongest evidence for efficacy has come from studies using D-cycloserine at a dose of 50 mg/day added to conventional antipsychotics in trials of 8 weeks duration or less.
  
  
  OBJECTIVE
  To assess the efficacy for negative symptoms and cognitive impairment of D-cycloserine augmentation of conventional antipsychotics in a 6-month trial.
  
  
  METHODS
  Fifty-five schizophrenia patients with prominent negative symptoms, treated with conventional antipsychotics, were randomly assigned to treatment with D-cycloserine 50 mg/day or placebo for 6 months in a double-blind, parallel group design.
  
  
  RESULTS
  Twenty-six subjects completed the 6-month trial; drop-out rates did not differ between treatment groups. D-Cycloserine treatment did not differ from placebo treatment on any primary outcome measure at 8 or 24 weeks, including response of negative symptoms and performance on a cognitive battery. Serum D-cycloserine concentrations did not correlate with response of negative symptoms.
  
  
  CONCLUSIONS
  D-Cycloserine did not exhibit therapeutic effects in this trial, possibly reflecting the high drop-out rate, a narrow range of therapeutic serum concentrations, a modest magnitude of therapeutic effect for the selected outcome measures, or loss of efficacy over time. Because D-cycloserine is a partial agonist with relatively low affinity for the glycine site, the magnitude of potential therapeutic effect may be smaller than that achieved by the higher-affinity full agonists, glycine and D-serine.
authors.affiliation: Schizophrenia Program, Massachusetts General Hospital, Boston, Mass., USA. goff@psych.mgh.harvard.edu
authors.forename: Donald C
authors.initials: DC
authors.lastname: Goff
authors.forename: Lawrence
authors.initials: L
authors.lastname: Herz
authors.forename: Thomas
authors.initials: T
authors.lastname: Posever
authors.forename: Vivian
authors.initials: V
authors.lastname: Shih
authors.forename: Guochuan
authors.initials: G
authors.lastname: Tsai
authors.forename: David C
authors.initials: DC
authors.lastname: Henderson
authors.forename: Oliver
authors.initials: O
authors.lastname: Freudenreich
authors.forename: A Eden
authors.initials: AE
authors.lastname: Evins
authors.forename: Iftah
authors.initials: I
authors.lastname: Yovel
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: David
authors.initials: D
authors.lastname: Schoenfeld
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000008:administration & dosage*; D003523:Cycloserine / Q000008:administration & dosage* / Q000097:blood; D004311:Double-Blind Method; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012559:Schizophrenia / Q000188:drug therapy*; D016896:Treatment Outcome
chemical_list: D014150:Antipsychotic Agents; D003523:Cycloserine