Background: Risperidone is the first atypical antipsychotic to become available in a long-acting, injectable formulation. This is the first prospective study to assess the effectiveness of long-acting risperidone in a cohort of bipolar patients.
Methods: Twenty-nine DSM-IV acutely manic bipolar inpatients with a history of poor or partial adherence to medication entered the mirror-design observational study. They received naturalistic treatment for a manic episode plus long-acting, injectable risperidone for a mean period of 2 years. The following measures were used to assess the effectiveness of risperidone: the number of hospitalizations, the number of manic, mixed, and depressive episodes leading to hospitalization, the mean duration of hospitalizations, time to relapse, treatment adherence, aggression and suicide attempts. The Clinical Global Impressions (CGI) was used for clinical relevance as well.
Results: During the follow-up, there was a significant decrease in the number of hospitalizations per patient (Z-2.72 P < 0.006), in the number of manic or mixed episodes leading to hospitalization (Z-2.68 P < 0.007) but not in the hospitalizations due to depressive episodes, a decrease in the average length of hospitalization per patient (Z-3.27 P < 0.001), a significant increase in the time to any new episode (first relapse) (Z-3.28, P < 0.001), and significant improvements in treatment adherence (P < 0.0001) and hetero-aggressive episodes (P < 0.0001), but not suicide attempts (P = NS). At study endpoint 14 patients (48%) were very much improved according to the CGI.
Discussion: This observational long-term study provides support to long-acting injectable risperidone being effective for the maintenance treatment of mania and improving treatment adherence, reducing relapses and re-hospitalization rates.