An assessment of emergent tardive dyskinesia and existing dyskinesia in patients receiving long-acting, injectable risperidone: results from a long-term study.

Introduction: Treatment-emergent tardive dyskinesia (TD) can be a serious side effect of antipsychotic treatment. Atypical antipsychotics are associated with a lower risk for TD than are conventional agents. A long-acting atypical antipsychotic, with more stable blood levels and lower peak blood levels than an oral formulation, may provide differential benefit regarding side effects, including movement disorders. This analysis assessed TD by defined research criteria in patients receiving long-acting, injectable risperidone.

Methods: Clinically stable subjects with schizophrenia or schizoaffective disorder participated in a 50-week, open-label trial of long-acting, injectable risperidone. TD was studied by defined research criteria (Schooler, N.R., Kane, J.M., 1982. Research diagnosis for tardive dyskinesia. Arch. Gen. Psychiatry. 39, 486-487; Americal Psychiatric Association, 2000. Diagnostic and Statistical Manual of Mental Disorders, fourth ed. American Psychiatric Association, Washington, DC). The severity of dyskinesia and other movement disorders were rated by the Extrapyramidal Symptom Rating Scale (ESRS).

Results: ESRS dyskinesia data were available for 662 patients. Five of 530 subjects without dyskinesia at baseline (0.94%) met the predefined criteria for emergent persistent TD during therapy. Based on either exposure to study medication or Kaplan-Meier analysis, the 1-year rate was 1.19%. Among the 132 subjects with dyskinesia at baseline, the mean score on the ESRS physician's exam for dyskinesia improved significantly at endpoint (-2.77; P<0.0001), regardless of anticholinergic drug use. (P=0.243 for patients with versus without anticholinergic drug use.)

Conclusions: In this open-label study, treatment with long-acting risperidone was associated with a low rate of emergent persistent TD. Significant improvement in existing dyskinesias was noted. The TD rate reported here is consistent with other reports of atypical antipsychotics and substantially lower than with conventional antipsychotics.