Patients with schizophrenia treated with long-acting injectable risperidone have significantly longer times to relapse than patients treated with oral quetiapine, according to a presentation at the annual meeting of the American Psychiatric Association.

The current trial, a 24-month, open-label, active-controlled, comparative international study, was the largest since a 1979 study to compare relapse rates of a long-acting injectable antipsychotic and an oral medication. The objective of the trial was to compare longer-term maintenance therapy of patients with schizophrenia or schizoaffective disorder treated with the injectable or oral antipsychotic medication.

"This study provides compelling evidence that risperidone long-acting injection (RLAI) offers a significant benefit to people with schizophrenia in delaying the time to relapse," said Professor Wolfgang Gaebel from the Department of Psychiatry and Psychotherapy at the Heinrich-Hein University in Dusseldorf, Germany and one of the study investigators.

The international study randomized 710 patients to injectable (mean dose, 32.75 mg) or oral medication (mean dose, 397 mg) and investigated whether treatment in a routine care setting within general psychiatric services had an effect on long-term efficacy maintenance as measured by time to relapse.

The average relapse-free time was significantly longer in patients treated with injectable long-acting risperidone (607 days) compared with oral quetiapine (533 days). Furthermore, over the 24-month treatment period, relapse occurred in 16.5 percent of patients treated with risperidone and 31.3 percent of patients treated with quetiapine.

Both medications had generally comparable safety profiles. Extra pyramidal symptoms attributed to medication were observed in 10 percent of patients receiving risperidone and 6 percent of patients receiving quetiapine. Weight gain was observed in both treatment arms with no statistically significant differences in change in body weight or body mass index versus baseline (7 percent weight gain for risperidone versus 6.2 percent for quetiapine). Potentially probating-related adverse events were observed in 16.7 percent of risperidone patients and 3 percent of quetiapine patients.

Reasons for withdrawing from the study other than relapse were comparable for the two treatment groups except there were more withdrawals due to non-compliance/refusing injection for risperidone (3 percent) than quetiapine (1 percent).