OBJECTIVE: The purpose of the present study was to evaluate the efficacy and tolerability of olanzapine long-acting injection for maintenance treatment of schizophrenia. METHOD: Outpatients with schizophrenia who had maintained stability on an oral regimen of olanzapine (10, 15, or 20 mg/day) for 4 to 8 weeks were randomly assigned to 24 weeks of double-blind treatment with "low" (150 mg every 2 weeks; N=140), "medium" (405 mg every 4 weeks; N=318), or "high" (300 mg every 2 weeks; N=141) doses of olanzapine long-acting injection; a very low reference dose of olanzapine long-acting injection (45 mg every 4 weeks; N=144); or their stabilized dose of oral olanzapine (N=322). Rates of and time to psychotic exacerbation were estimated using Kaplan-Meier methodology. RESULTS: At 24 weeks, the majority of oral olanzapine-treated patients (93%), as well as most olanzapine long-acting injection-treated patients receiving high (95%), medium (90%), low (84%), and very low doses (69%), remained exacerbation free, with the therapeutic 4-week regimen (medium dose) and pooled 2-week regimen (low and high doses) demonstrating efficacy similar to that of oral olanzapine as well as to each other. The three standard long-acting doses were superior to the very low reference dose based on time to exacerbation. Incidence of weight gain > or = 7% of baseline was 21% for oral olanza-pine compared with 21%, 15%, 16%, and 8% for the high, medium, low, and very low olanzapine long-acting treatment groups, respectively. No clinically significant differences were observed between the long-acting injection and oral olanzapine groups in general safety parameters. Few injection-site reactions occurred (3%). Two patients experienced sedation and delirium consistent with olanzapine overdose following possible accidental intravascular injection. CONCLUSIONS: Olanzapine long-acting injection was efficacious in maintenance treatment of schizophrenia for up to 24 weeks, with a safety profile similar to oral olanzapine except for injection-related adverse events.
