Long-term efficacy and safety of once-monthly Risperidone ISM® in the treatment of schizophrenia: Results from a 12-month open-label extension study

Objective To evaluate long-term efficacy, safety and tolerability of Risperidone ISM® in patients with schizophrenia, a multicenter, open-label extension of the PRISMA-3 study was conducted. Methods Eligible placebo (unstable) and Risperidone ISM® (stabilized) rollover patients from a previous 12-week double-blind phase and de novo stable patients received once-monthly intramuscular injections of Risperidone ISM® 75 or 100 mg for 12 months. The long term-efficacy assessment included the Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression-Severity (CGI-S) and Clinical Global Impression-Improvement (CGI-I) scales. Safety evaluation included treatment-emergent adverse events (TEAEs), injection site reactions (ISR), laboratory tests and several safety scales. Results Altogether, 215 patients entered the study (55 unstable, 119 stabilized and 41 stable patients). Most patients (74.9%) completed, and discontinuation rates were broadly similar across the study subgroups, mainly due to withdrawal of consent (12.1%). PANSS total and subscales scores decreased from baseline to endpoint in all groups, with the largest decrease for unstable patients. Improvement from baseline to 12 months was also shown for CGI-S and CGI-I scores for both unstable and stabilized patients; the CGI-S and CGI-I scores remained almost unchanged for the stable group. At least one treatment-related TEAE was reported in 39.1% of patients; the most common were headache (12.1%), hyperprolactinemia (9.8%) and asthenia (5.1%). ISR were reported in 8 (0.3%) patients; injection site pain score was low across the 2355 doses assessed. Conclusion Risperidone ISM® is an effective, safe, and well-tolerated long-term treatment of schizophrenia in adults, regardless of the initial disease severity or whether patients were previously treated with Risperidone ISM® during an acute exacerbation or switched from stable doses of oral risperidone.