Background. Tardive dyskinesia (TD) is a therapy-resistant
adverse effect of neuroleptics.
Although the exact pathophysiology of TD is unknown, oxygen radicals have
to play a role in TD based on several lines of evidence. Superoxide dismutase
(SOD) is a key
enzyme which scavenges oxygen radicals. The authors investigated the
association between erythrocyte SOD activity and TD.
Methods. Erythrocyte SOD activities were measured, blinded
to the presence or absence of
TD, in 30 patients with schizophrenia who had been on typical neuroleptics
for more than 10
years. TD severity was independently assessed, using the abnormal
involuntary movement scale (AIMS), by two raters.
Results. There was a significant decrease in erythrocyte
SOD activity in the definite TD group
(N=10) as compared with the no TD (N=8) and questionable
TD (N=12) groups.
Erythrocyte Cu,Zn-SOD activities correlated with AIMS scores.
Conclusions. Patients with TD had low SOD activities as
compared to those without TD. As a
causal link between SOD activity and TD was not established in this study,
studies are warranted to determine whether patients with low SOD activity
are susceptible to neuroleptic-induced TD.