MK0249 for the Treatment of Cognitive Impairment in Patients With Schizophrenia (0249-016)

• Mean Change From Baseline at 4 Weeks of Treatment in Attention/Processing Speed Composite Score [ Time Frame: Baseline and 4 weeks of treatment ] [ Designated as safety issue: No ]
  The Attention/Processing Speed Composite Score was comprised of the University of Pennsylvania's Computerized Neuropsychological Battery (CNP) Penn Continuous Performance Test (PCPT) and BACS battery Symbol Coding. The composite score was calculated as a weighted average of the T-scores (normalized for age) for each test. The minimum and maximum values possible for this composite T-score of the change from baseline were -91 and 91, respectively. Higher values (positive changes from baseline) indicate better performance.
• Mean Change From Baseline at 4 Weeks of Treatment in Episodic Memory Composite Score [ Time Frame: Baseline and 4 weeks of treatment ] [ Designated as safety issue: No ]
  The Episodic Memory Composite Score was comprised of the University of Pennsylvania's Computerized Neuropsychological Battery (CNP) Face Memory and BACS battery Verbal Memory. The composite score was calculated as a weighted average of the T-scores (normalized for age) for each test. The minimum and maximum values possible for this composite T-score of the change from baseline were -202 and 202, respectively. Higher values (positive changes from baseline) indicate better performance.
• Mean Change From Baseline at 4 Weeks of Treatment in Working Memory Composite Score [ Time Frame: Baseline and 4 weeks of treatment ] [ Designated as safety issue: No ]
  The Working Memory Composite Score was comprised of the University of Pennsylvania's Computerized Neuropsychological (CNP) battery N-back test and the BACS battery Digit Sequencing test. The composite score was calculated as a weighted average of the T-scores (normalized for age) for each test. The minimum and maximum values possible for this composite T-score of the change from baseline were -122 and 122, respectively. Higher values (positive changes from baseline) indicate better performance.

The purpose of this study is to determine the safety and effectiveness of an investigational drug MK0249 for the treatment of the cognitive impairment in patients with schizophrenia.

• Drug: MK0249
  MK0249 10mg (2 x 5 mg) tablet daily (qd) for 28 days.
• Drug: Comparator: Placebo (unspecified)
  MK0249 10mg (2 x 5 mg) Pbo tablet qd for a 28 day treatment period.

• Experimental: MK0249
  Intervention: Drug: MK0249
• Placebo Comparator: Placebo
  Intervention: Drug: Comparator: Placebo (unspecified)

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
• Females are not pregnant, and those who can have children agree to remain abstinent or use acceptable birth control throughout the 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
• Patient has total Positive and Negative Syndrome Scale (PANSS) score between 36 and 75 at screening and at the first baseline visit
• Patient has a Clinical Global Impressions - Severity (CGI-S) score less than or equal to 4 at screening and at the first baseline visit

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 or clozapine 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 the past 5 years
• Patient has a history of alcohol or drug dependence within the past year or alcohol or drug abuse within 3 months of screening