Reported Adverse Drug Reaction Cases
- Kane JM. Tardive dyskinesia rates with atypical antipsychotics in adults: prevalence and incidence. J Clin Psychiatry 2004; 65 (Suppl. 9): 16 -20.
- Tarsy D and Baldessarini RJ. Epidemiology of tardive dyskinesia: Is risk declining with modern antipsychotics? Movement Disorders 2006; 21: 589-598.
Atypical antipsychotic agents and extrapyramidal side effects
It has been suggested that the atypical antipsychotic agents clozapine, risperidone, olanzapine, aripipazole and quetiapine may have lower propensity for causing extrapyramidal side effects (EPS) when compared with older antipsychotic agents such as haloperidol, chlorpromazine and thioridazine.1,2 However, studies comparing the incidence of EPS between the older and newer agents are often confounded, especially by previous exposure to older agents.2
ADRAC data were searched for reports of EPS in association with the newer antipsychotic agents, using terms relating to nervous system disorders and movement disorders. The number of these reports, as well as total number of reports involving the medicine, is shown in the following Table. Reports for haloperidol are included for comparison.
| Medicine | Total reports | EPS reports (% of total) |
| Aripiprazole | 147 | 33 (22.4) |
| Risperidone | 812 | 159 (19.6) |
| Quetiapine | 315 | 42 (13.3) |
| Olanzapine | 1203 | 126 (10.5) |
| Clozapine | 3775 | 70 (1.9) |
| Haloperidol | 753 | 321 (42.6) |
These data should be interpreted with caution. As with most data from spontaneous reporting, the data do not take into account factors influencing reporting rates, such as level of usage and intensive post-market safety monitoring programs. Reports with the newer agents are also likely to be confounded as described above, and ADRAC data for haloperidol are likely to be substantially more incomplete and limited than data for the newer agents. Therefore, the relative numbers of EPS reports shown in the Table do not necessarily reflect relative risk between these agents.
The ADRAC data suggest that, while the incidence of EPS may be lower with atypical antipsychotics than with the older agents, atypical antipsychotic agents are not devoid of EPS.
The most common reactions described in reports with the newer antipsychotic agents include dystonias, dyskinesias, akathisia and other non-specified EP disorder. At the time of reporting, about one third of patients experiencing EPS had not recovered, with no distinction between medicines in this regard.
ReferenceReference
Australian Adverse Drug Reactions Bulletin, Volume 26, Number 4 (August 2007)