One of the more common side effects from conventional neuroleptics is tardive dyskinesia. This side effect can be a significant problem because it tends to persist and is sometimes irreversible. Two risk factors for this side effect include older age and the cumulative neuroleptic amount. The one-year incidence of cumulative tardive dyskinesia reported in the literature is approximately 25 percent. The atypical antipsychotic agent risperidone has a much lower incidence of this side effect. However, few studies have looked at long-term therapy with this agent. Jeste and associates studied the incidence of tardive dyskinesia in elderly patients with dementia who are being treated with risperidone.
Patients with Alzheimer's disease, vascular dementia or mixed dementia who had indications for neuroleptic therapy were enrolled in a one-year, open-label study. They were evaluated at baseline and every two months. Dosages of risperidone were 0.5 to 2.0 mg per day, based on patients' response. Persistent emergent tardive dyskinesia was defined by the scores on the dyskinesia subscale of the Extrapyramidal Symptom Rating Scale. Among the 330 patients enrolled in the study, the mean age was 82.5 years. The mean dosage of risperidone was 0.96 mg per day, and the median length of use was 230 days. The one-year accumulative incidence of persistent tardive dyskinesia in patients without dyskinesias at baseline was 2.6 percent. Patients with dyskinesia symptoms at baseline experienced a significant reduction in the severity of their symptoms during the study period. Patients who received 0.75 to 1.5 mg per day of risperidone showed the best improvement in psychopathologic symptoms over the study period.
The authors conclude that the incidence of persistent tardive dyskinesia with risperidone treatment for psychopathology in elderly patients with dementia seemed to be much lower than the incidence in those treated with conventional neuroleptics. The average optimal dosage of risperidone in elderly patients with dementia is 0.75 to 1.5 mg per day.