Background: While several clinical trials showed that atypical antipsychotics have a low risk of extrapyramidal side effects (EPS), this observation is not undisputed. This study compared the risk of EPS between specific subgroups of antipsychotics.
Methods: Using the automated dispensing records of a large psychiatric hospital in The Netherlands, we defined cases as first-time users of anticholinergic antiparkinson drugs. Controls were all patients with no recorded use of such medication. Cases and controls were compared with regard to previous use of antipsychotics and relevant co-factors.
Results: Out of 1403 patients, we identified 105 cases and 330 controls. Compared to non-users, antipsychotic-users were 10 times more likely to start with anticholinergic antiparkinson medication (adjusted odds ratio: 10.1; 95 CI 4.6-22.3). Depot and non-depot antipsychotics had similar adjusted odds ratios of 10.9 (95 CI 3.7-32.6) and 8.8 (95% CI 3.8-20.4) respectively. Low and high potency antipsychotics gave odds ratios of 3.0 (95% CI 0.9-10.3) versus 10.8 (95% CI 4.7-25.1). Classical and atypical antipsychotics showed comparable odds ratios: 10.0 (95% CI: 4.4-22.5) versus 8.0 (95% CI: 2.6-24.5). Applied doses of classical and atypical antipsychotic drugs were much lower and more equivalent than those used in previous clincial trials.
Conclusions: Low potency antipsychotics had a much lower risk of EPS than other antipsychotics. However, we did not corroborate the reduced risk with atypical antipsychotics observed in several clinical trials. This discrepancy may result from the high and non-equivalent doses of classical antipsychotics used in many of these trials.