• Efficacy will be determined by measuring the time (in days) from randomization to event/relapse; relapse will be assessed by clinical status, rating scale changes, and pharmacologic stability in double-blind phase. [ Time Frame: 52 weeks ] [ Designated as safety issue: No ]
  

• Safety and tolerability as assessed by adverse event reports (every 2 weeks), scores on movement disorder measures, laboratory parameters, vital signs, ECG measures and physical examination reports (every 2-3 months) [ Time Frame: 52 weeks ] [ Designated as safety issue: No ]
  

Frequently-relapsing (more than 4 episodes in the last year) bipolar patients are a sub-group of patients who have multiple mood episodes in spite of treatment. Currently available treatments may have little impact on number and frequency of manic and/or depressed mood episodes and as a result, these patients have higher than average rates of illness and death. This study examines the effectiveness and side effects of risperidone long-acting injections (LAI) added to treatment as usual (TAU) in frequently-relapsing bipolar patients. The study has two main phases. The first phase is open-label (patients and doctors know what medication and dose the patient is receiving- both risperidone LAI and TAU) and lasts 16 weeks. During that time, patients are treated with the goal that they reach "remission", a predefined level of improvement (decrease in number and severity of mood episodes.) Patients who meet remission criteria at the end of the first phase are randomized (like flipping a coin) to either continue receiving the same dose of risperidone LAI plus TAU, or placebo injections plus TAU. Patients continue in the second phase for 52 weeks, during which time the effectiveness is measured by time to "relapse" (worsening of mood symptoms severe enough to require hospitalization or a major change in medication.) Additional effectiveness, safety, and side effect measures are evaluated throughout the length of the study.

Long-acting risperidone injection 25 mg will be administered every two weeks through a gluteal injection for at least one month. Thereafter, the dose may be increased to 37.5mg then to 50 mg based on clinical response and tolerability. Supplemental use of oral Risperdal (1 to 2 mg/day) will be permitted during the first 12 weeks of the Open-Label Stabilization Phase. Patients must be taking a stable dose of risperidone LAI for the 4 weeks immediately prior to entering the Double-Blind Phase.