• adjunctive;
  • bipolar disorder;
  • long-acting injectable;
  • relapse;
  • risperidone

Objective:  No large controlled trials have evaluated adjunctive maintenance treatment with long-acting injectable antipsychotics in patients with bipolar disorder. This study assessed whether adjunctive maintenance treatment with risperidone long-acting therapy (RLAT), added to treatment-as-usual (TAU) medications for bipolar disorder, delays relapse in patients with bipolar disorder type I.

Methods:  This study included patients with bipolar disorder type I with ≥ four mood episodes in the 12 months prior to study entry. Following a 16-week, open-label stabilization phase with RLAT plus TAU, remitted patients entered a 52-week, double-blind, placebo-controlled, relapse-prevention phase. Randomized patients continued treatment with adjunctive RLAT (25–50 mg every two weeks) plus TAU (n = 65) or switched to adjunctive placebo injection plus TAU (n = 59). The primary outcome measure was time to relapse to any mood episode.

Results:  Of 240 enrolled patients, 124 entered double-blind treatment. Time to relapse was longer in patients receiving adjunctive RLAT (p = 0.010). Relapse rates were 23.1% (n = 15) with adjunctive RLAT versus 45.8% (n = 27) with adjunctive placebo; relative relapse risk was 2.3-fold higher with adjunctive placebo (p = 0.011). Completion rates were: adjunctive RLAT, 60.0% (n = 39) and adjunctive placebo, 42.4% (n = 25; p = 0.050). Adverse event (AE)-related discontinuations were 4.6% (n = 3) and 1.7% (n = 1), respectively. Common AEs (adjunctive RLAT versus adjunctive placebo) were: tremor (24.6% versus 10.2%), insomnia (20.0% versus 18.6%), muscle rigidity (12.3% versus 5.1%), weight increased (6.2% versus 1.7%), and hypokinesia (7.7% versus 0.0%).

Conclusions:  Adjunctive RLAT significantly delayed time to relapse in patients with bipolar disorder type I who relapse frequently. Safety and tolerability of RLAT were generally consistent with that previously observed.