Aims: This 12-week open-label study was designed to investigate the pharmacokinetics and efficacy of a direct switch from a conventional depot to long-acting injectable risperidone in patients with schizophrenia and schizoaffective disorder.
Methods: Men or women from 18 to 65 years old with a diagnosis of schizophrenia or schizoaffective disorder were eligible for participation if they had been treated with conventional depot for at least 8 weeks before study entry. Intramuscular long-acting risperidone was administered starting from 25 mg, with the dose flexibly adjusted every two weeks for 12 weeks from week 4.
Results: Of the 25 patients enrolled in this study, 21 completed at least one post-baseline assessment and were thus included in the analysis. The mean serum concentration of risperidone plus 9-hydroxyrisperidone was 29.1 ng/mL at the 12th week after switching, with an average injection dose of 31.25 mg long-acting risperidone every two weeks. The levels of active moiety of risperidone seemed to be higher in Chinese patients compared to those in Caucasian patients. Positive and Negative Syndrome Scale total scores (from 67.5 to 56.4; P = 0.002), scores for negative symptoms (P = 0.006) and general symptoms (P = 0.001) were improved significantly 12 weeks after the switch. Mean Extrapyramidal Symptom Rating Scale scores were improved significantly from 20.1 to 5.5 (P < 0.001). Significantly decreased levels of cholesterol and triglyceride were found at the 12th week. The levels of fasting glucose, low-density lipoprotein, high-density lipoprotein and bodyweight remained unchanged.
Conclusions: These findings suggest that switching from conventional depot to long-acting risperidone is feasible with the advantage of symptom reduction and side-effect profile decrement.