MK0557 for the Treatment of Cognitive Impairment in Patients With Schizophrenia (0557-027)

A Phase IIa, Randomized, Double-Blind, Placebo-Controlled, 2-Period, Cross-Over Clinical Trial to Study the Safety and Efficacy of MK0557 for the Treatment of Cognitive Impairment in Patients With Schizophrenia

The purpose of this study is to determine the safety and effectiveness of an investigational drug for the treatment of cognitive impairment in patients with schizophrenia.

Inclusion Criteria:

• Patient is clinically stable, on current antipsychotic medication for at least 3 months and current dose for 2 months
• Patient has a 6th grade reading level or better and has completed at least 6 years of formal education
• Females are not pregnant, and those who can have children agree to remain abstinent or use acceptable birth control throughout study
• Patient has had a stable living arrangement for at least 3 months prior to study start
• Patient is in general good health based on screening assessments

Exclusion Criteria:

• Patient has a major disease/disorder that may interfere with cognitive testing (such as mental retardation) and/or pose a risk upon study participation
• Patient has a history of head trauma with loss of consciousness greater than 15 minutes
• Patient has had warfarin treatment, MAO inhibitors, clonazepam, clozapine or St. John's wort within 1 month of screening
• Patient has had ECT treatment within 6 months of screening
• Patient requires treatment with antihistamines or certain other medications listed in the protocol
• Patient has a history of liver disease that has been active within the last 2 years, or a history of cancer within past 5 years
• Patient has a history of alcohol or drug dependence within past year or alcohol or drug abuse within 3 months of screening