Clinical experience in developing treatment regimens with the novel antipsychotic risperidone

Early intervention with antipsychotic treatment has been shown to reduce the risk of relapse and to improve long-term morbidity in patients with schizophrenia. However, treatment with conventional neuroleptics carries with it a significant risk of developing extrapyramidal side effects. Conventional neuroleptics exert their antipsychotic effects at doses similar to those that cause extrapyramidal side effects. Although anticholinergic medication (e.g. benztropine) may reduce the severity of these side effects, anticholinergics are themselves associated with significant side effects, such as dry mouth, constipation, blurred vision, urinary retention and sexual dysfunction. Anticholinergic drugs are also associated with impaired cognition and worsening of the patient's psychosis. Newer antipsychotic drugs, such as risperidone, which have a dual mechanism of action (serotonin-dopamine antagonism) are reported to have a lower risk of extrapyramidal side effects than conventional agents. In particular, risperidone produces significant antipsychotic effects at doses lower than those that cause extrapyramidal side effects. Patients presenting with a first episode of psychosis and who are antipsychotic drug-naïve may exhibit abnormal movements before treatment is initiated. Unless these patients are carefully assessed at baseline these movements could be mistaken for drug-induced extrapyramidal side effects. It is important to develop treatment strategies for these patients that improve positive and negative psychotic symptoms as quickly as possible, with a minimal risk of extrapyramidal side effects developing. Prompt and appropriate antipsychotic treatment can substantially reduce the risk of relapse. Whereas approximately 60% of unmedicated patients will relapse in the first year following resolution of the acute psychotic episode, prophylactic antipsychotic medication can reduce this rate to less than 20%. Recent clinical experience in Canada has shown that risperidone is effective in the treatment of patients with first-episode psychosis. Moreover, lower doses of risperidone were required than those previously used to treat chronically ill patients with a history of multiple psychotic episodes and prolonged exposure to conventional neuroleptics. As further data are accumulated, the mean daily dose of risperidone required by first-episode patients has been shown to be close to 4 mg. The low incidence of extrapyramidal side effects in these patients (< 10% required anticholinergic medication) supports the use of risperidone and offers the prospect of improved compliance and a better long-term outcome.