To the Editor: Tardive dyskinesia is a serious and potentially debilitating problem for patients treated with conventional antipsychotics. The general treatment guideline for tardive dyskinesia is to change from treatment with conventional to atypical antipsychotics after a patient fails to response to a decreased dose of conventional antipsychotics. Chouinard +(1) found that 6 mg/day of risperidone had a beneficial effect on tardive dyskinesia in a double-blind 8-week trial. But we know of no long-term follow-up studies regarding the severity of tardive dyskinesia after patients are shifted from treatment with conventional antipsychotics to risperidone.

Ten male patients, who met DSM-IV criteria for schizophrenia and research diagnostic criteria by Schooler and Kane +(2) for tardive dyskinesia, were enrolled in our study. The subjects provided their written informed consent to participate. Their original conventional antipsychotics and antiparkinsonian drugs were tapered within 1 week of their entry into the study. Risperidone was prescribed at 2 mg/day and gradually increased to 8 mg/day within 4 weeks. The optimal dose of risperidone was adjusted to maintain the least severity of tardive dyskinesia. The severity of tardive dyskinesia was evaluated with the Abnormal Involuntary Movement Scale (AIMS) +(3) at weeks 1, 2, 3, 4, 6, 8, 10, 12, 24, 36, and 52 of follow-up. All ratings were performed in the afternoon by two senior psychiatrists (J.-Y.C. and C.-C.L.). The patients whose final AIMS scores decreased by more than 4 points were defined as responders, and those whose scores decreased less than 4 points were deemed nonresponders. One patient dropped out because of a physical illness.

The final result showed that there were five responders (55.6%) and four nonresponders (44.4%). The mean final risperidone dose for all nine patients was 6.7 mg/day. The five patients who improved got their maximum effect at a dose of 6.0 mg/day. There was no significant difference in baseline AIMS scores for the responders and nonresponders (mean=13.4, SD=3.8, versus mean=11.7, SD=0.4, respectively). At the endpoint the mean change in AIMS score was 7.0 (SD=2.7) for the responders and 0.5 (SD=0.5) for the nonresponders.

Some tardive dyskinesia is reversible and may spontaneously disappear after withdrawal of neuroleptics, but in the 40-week follow-up study by Glazer et al. +(4) complete remission was rare (2%). The severity of dyskinesia decreased in only 20% of the patients who stopped taking neuroleptics, and the rate of a relapse into psychosis approached 50%. Neuroleptic withdrawal is risky, with a high rate of psychosis exacerbation. All of our patients maintained a stable condition, and five patients had substantial improvement of tardive dyskinesia. As far as we know, this is the first 1-year follow-up case series regarding the use of risperidone with patients with tardive dyskinesia. The antidyskinetic effect of risperidone should be confirmed with a double-blind, controlled trial in a larger study group.