Antipsychotics and Seizures: Which Antipsychotic Has a Higher Risk?

In the journal Seizure: European Journal of Epilepsy, articles ahead of print, Doctors Lertxundi and colleagues from a number of institutions in Spain present an interesting analysis looking at the risk of antipsychotic treatment and seizures as a side effect to the use of those drugs. The authors noted that almost all antipsychotic medications have been reportedly associated with a risk of causing seizures. Among the first generation antipsychotics, chlorpromazine appears to be the one most associated with the greatest risk of seizures, whereas in the newer antipsychotics clozapine is thought to be the most likely to cause seizures of that group of medications. The authors sought out to investigate if these beliefs are true based on a review of a database of a network of centers of the Spanish Pharmacovigilance System that provides reporting data for adverse reactions from the entire Pharmacovigilance System and calculated the risk ratio or odds ratio for seizures in antipsychotics in Spain. The database was reviewed from the years 1984 through June 2011.

The authors found that the total number of convulsions reported for second generation antipsychotics was 169; whereas the number of convulsions reported for first generation antipsychotics, was 35. First generation antipsychotics included: chlorpromazine, fluphenazine, haloperidol, perphenazine, thioridazine and others. Ninety-four convulsions were reported in association with clozapine alone and the odds ratio for clozapine vs. chlorpromazine was 3.2. The odds ratio excluding clozapine was 2.08. The results show that second generation antipsychotics pose a higher risk of seizures than first generation, mostly due to clozapine but also in association with other medications that are in this group as well ( most notably olanzapine, quetiapine, and resperidone). This is consistent with studies that suggest that second generation antipsychotics have a higher average risk of EEG abnormalities in the first generation antipsychotics.

This study is important because it highlights a common side effect of a medication that can be utilized for treatment of complications associated with seizures, particularly those that have postictal psychosis and other similar problems. As a result, this study helps to solidify our knowledge of which medications we need to avoid when treating those psychotic disorders in patients with epilepsy.