A Study to Evaluate the Effect of Oral Paliperidone Extended-Release and Oral Risperidone Immediate-Release on Cognitive Function in Clinically Stable Patients With Schizophrenia

• Change in category fluency score of cognitive function scale (Cognitive Abilities Screening Instrument, Chinese version [CASI C-2.0]) from baseline to Week 24 [ Time Frame: Baseline (Week 0), Week 4, Week 12 and Week 24 ] [ Designated as safety issue: No ]
  CASI C-2.0 will be used to measure patient's cognitive ability. The range of CASI score is 0 to 100 (a higher score indicating better performance and is influenced by patient's educational level). The CASI C-2.0 provides quantitative assessment on 9 cognitive domains and 20 questions, including attention, concentration, orientation, short-term memory, long-term memory, language abilities, visual construction, category fluency, abstraction, and judgment.
  
  

• Change from baseline to Week 24 in score of Modified Wisconsin Card Sorting Test (MWCST) short version [ Time Frame: Baseline, Week 4, Week 12 and Week 24 ] [ Designated as safety issue: No ]
  The WCST was developed to assess abstract reasoning and ability to shift cognitive strategies in response to environmental changes. The materials consist of a pack of 4 stimulus cards and 48 response cards which are devised so that each card contains from 1 to 4 identical figures of a single color. Individually administered, it requires the patient to sort the cards according to different principles (ie, by color, form, or number). As the test progresses, there are unannounced shifts in the sorting principle which require the patient to alter his or her approach.
  
  
• Change from baseline in score of Continuous Performance Test (CPT) [ Time Frame: Baseline, Week 4, Week 12 and Week 24 ] [ Designated as safety issue: No ]
  CPT is an attention test. Response patterns on the CPT II is used as an aid in monitoring treatment effectiveness. For example, some response patterns suggest inattentiveness or impulsivity, while other response patterns may indicate activation/arousal problems or difficulties maintaining vigilance.
  
  
• Change from baseline in score of Personal and Social Performance (PSP) scale [ Time Frame: Baseline, Week 4, Week 12 and Week 24 ] [ Designated as safety issue: No ]
  The PSP is a clinician-rated instrument providing an overall rating of personal and social functioning in subjects with schizophrenia on a scale of 1-100. Four domains of functioning are considered in the rating: 1) socially useful activities, including work and study, 2) personal and social relationships, 3) self-care, and 4) disturbing and aggressive behavior.
  
  
• Change from baseline in score of Positive and Negative Syndrome Scale (PANSS) [ Time Frame: Baseline, Week 4, Week 12 and Week 24 ] [ Designated as safety issue: No ]
  The PANSS is a medical scale used for measuring symptom severity of patients with schizophrenia. The neuropsychiatric symptoms of schizophrenia will be assessed using the 30-item PANSS scale, which provides a total score (sum of the scores of all 30 items). Each scale is rated 1 (absent) to 7 (extreme).
  
  
• Change from baseline in score of Clinical Global Impression-severity (CGI-S) scale [ Time Frame: Baseline, Week 4, Week 12 and Week 24 ] [ Designated as safety issue: No ]
  The CGI-S rating scale is used to rate the severity of a patient's psychotic condition on a 7-point scale ranging from 1 (not ill) to 7 (extremely severe). This scale permits a global evaluation of the patient's condition at a given time.
  
  
• Change from baseline in score of Medication Satisfaction Questionnaire (MSQ) [ Time Frame: Baseline, Week 4, Week 12 and Week 24 ] [ Designated as safety issue: No ]
  MSQ is designed to assess treatment satisfaction among patients with schizophrenia. It consists of 1 question: "Overall, how satisfied are you with your current antipsychotic medication(s)?" with responses assessed on a 7-point scale rated as follows: 1=extremely dissatisfied, 2=very dissatisfied, 3=somewhat dissatisfied, 4=neither satisfied nor dissatisfied, 5=somewhat satisfied, 6=very satisfied, and 7=extremely satisfied.
  
  

This is a 28-week, randomized (the study medication is assigned by chance), open-label (all people know the identity of the intervention), active-controlled (patients are assigned to either a recognized effective treatment or the study medication) comparative study. All patients will enter a run-in period to receive a stable therapeutic dose of oral risperidone immediate-release for at least 4 weeks. After the 4-week run-in period, patients will be randomly assigned to either remain on oral risperidone immediate-release (IR) or to receive a therapeutic dose of oral paliperidone extended-release (ER) and patients will be prospectively followed for a 24-week treatment phase. The treatment phase is composed of a 4-week flexible dose period followed by a 20-week stable dose period. During the 4-week flexible dose period, the dose of paliperidone ER or risperidone IR may be increased or decreased for each patient if clinically indicated (eg, significant side effects emerge or there is evidence of a lack of efficacy). At the end of 4-week flexible dose period, the final dose should be maintained for the 20-week fixed-dose period. Efficacy and safety will be assessed at baseline (Week 0) and Weeks 4, 12, and 24.