• To assess the impact of switching subjects from an existing antipsychotic to risperidone long acting on healthcare resource utilization. This will be evaluated by assessing: [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Direct cost of care [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Frequency and duration of institutional care [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Discharge [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Relapse [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  

• To determine if effectiveness is maintained for subjects switched from an existing antipsychotic to risperidone long acting. This will be evaluated by assessing: [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Positive and negative symptoms (PANSS) [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Overall illness severity (CGI severity, CGI improvement) [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Social and occupational functioning (SOFAS), and [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Remission [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• To evaluate the safety and tolerability of risperidone long acting. This will be evaluated by assessing: [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Extrapyramidal symptoms (ESRS) [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Side effects (UKU side effect rating scale) [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Akathisia (Barnes akathisia scale) [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Quality of life (SF-36) [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Weight, and waist circumference [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  
• Hematology (fasting glucose and lipid analysis) [ Time Frame: Unspecified ] [ Designated as safety issue: No ]
  

Drug: Risperidone
See Detailed Description.

Screening (Week -2 to Week 0; Days -14 to -1) In this phase, the subject is required to be treated with oral risperidone (as their only antipsychotic) for a period of at least 5 days before entering the stabilization phase of the study. Therefore,

• If the subject is currently treated with an antipsychotic other than risperidone, the dosage will be tapered gradually and discontinued. Simultaneously, oral risperidone will be started at 2 mg/day and increased to no more than 6 mg/day. The subject will be treated with risperidone monotherapy for at least five days prior to entering the stabilization phase of the study.
• On the other hand, if the patient has already been treated for more than 5 days with risperidone monotherapy then he/she may enter the stabilization phase of the study immediately.

Stabilization Phase (Weeks 1 - 14; Days 0 - 98) The first three doses of risperidone long acting (Days 0, 14 and 28) will be 25 mg for all subjects. At the time of the fourth injection (Day 42), the dosage of risperidone long acting may be increased from 25 mg IM to 37.5 mg IM upon discretion of the treating physician. Further increases in the dosage of risperidone long acting may be made at the time of the 6th and 8th injections (Days 70 and 98 respectively). In this case, if the subject is currently receiving 25 mg he/she may be increased to 37.5 mg but not 50 mg. Alternatively, if the patient is currently receiving 37.5 mg, then subject may be increased to the maximum recommended dosage of 50 mg IM every two weeks.

To accommodate for the latency period (i.e., the time for risperidone to be released from the microspheres and approach therapeutic plasma levels), subjects entering into the study will continue on oral risperidone for the first three weeks (Days 0-21). Temporary oral supplementation will also be permitted anytime during the stabilization phase of the study when considered by the treating physician to be clinically necessary for the treatment of breakthrough psychosis. With only one exception, the treating physician is not restricted from adding or discontinuing any pharmacological treatment deemed necessary for the clinical management of the subject. The exception in this case prohibits the addition of another antipsychotic agent and applies only to the stabilization phase of the study.

Maintenance Phase (Weeks 15 - 38; Days 99 - 266) Patients that have shown adequate response to risperidone long acting will continue into the maintenance phase of the study. From this point onwards, the treating physician may change the dosage of risperidone long acting at any time as considered necessary. Temporary oral supplementation will also be permitted during the maintenance phase when considered by the treating physician to be clinically necessary for the treatment of breakthrough psychosis. Apart from the above, the treating physician is not restricted from adding or discontinuing any pharmacological treatment (including another antipsychotic) deemed necessary for the clinical management of the subject.