Tardive dystonia provoked by concomitantly administered risperidone

Two cases of tardive dystonia are reported. The first case was an 18-year-o ld schizophrenic woman suffering from parkinsonism and hypotension induced by antipsychotic drugs. Risperidone (4 mg/day) was added to her drug regime n and after increasing the dosage to 6 mg/day, she began to exhibit retroco llis. The second case was a 61-year-old woman who had schizophrenia and tar dive dyskinesia. After replacing chlorpromazine (75 mg/day) with risperidon e (4 mg/day), she began to exhibit retrocollis. The retrocollis in both cas es was considered to be tardive dystonia provoked by risperidone administer ed concomitantly with other antipsychotics. Risperidone is reported to prod uce few extrapyramidal symptoms, but these cases suggested that changing fr om other drugs to risperidone, or rapidly increasing risperidone dosage, ma y provoke tardive syndrome.