Efficacy Study on Cognitive Functions in Schizophrenic Patients

Inclusion Criteria: * Diagnosis: DSM-IV schizophrenia (any subtype) * Duration of illness: ≥ 5 years * Concomitant standing or prn medications (except other antipsychotics and those contraindicated in the respective package inserts \[amisulpride or risperidone\]) are permitted during treatment phase, if they were present at a stable dose for at least 6 weeks prior to the start of initial treatment with study medication * Overall symptom severity: patients must evidence a total score of 60 or higher on the PANSS scale * Clinical Symptoms: A score of 4 (moderate) or greater on any of the 7 items of the PANSS Positive Symptom Subscale is present * Cognitive status (minimum performance level): subject must be able to validly complete the baseline MATRICS assessment * Clinical judgment by the investigator that treatments with amisulpride or risperidone are warranted due to suboptimal clinical outcome despite previous treatments Exclusion Criteria: * Past or current intolerance of amisulpride or risperidone side effects that are judged by the investigator to be unsafe, dose-limiting, or likely to result in study discontinuation. * Any contraindication for amisulpride or risperidone therapy as indicated in the drug description. * Presence of any unstable or untreated medical disorder. * Any history of seizures or seizure disorder other than febrile seizures of childhood; * History of positive hepatitis B surface antigen. * Any abnormal laboratory test that is judged to be clinically significant by the investigator. * A history of significant head injury/trauma, as defined by: A. loss of consciousness (LOC) for more than 1 hour B. recurring seizures resulting from the head injury C. clear cognitive sequelae of the injury D. cognitive rehabilitation following the injury * Alcohol or substance dependence within the past 12 months or abuse within the past 3 months. Any subject with positive urine toxicology or alcohol use that is considered abnormal at baseline. * Clinically significant suicidal or homicidal behavior or attempts within past 6 months. * Pregnant or breast-feeding women * Absence of medically approved contraceptive methods for female of childbearing potential. The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.