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Electroencelphalogram Abnormalities Appear Less Frequent With Quetiapine Than With Haloperidol and Olanzapine

The rate of electroencephalogram (EEG) abnormalities in patients taking quetiapine is significantly lower than in those taking haloperidol and olanzapine, and is comparable to the rate of EEG abnormalities in healthy individuals, German researchers have found.

General slowing of background activity, an increase in paroxysmal theta or delta activity, and the development of epileptiform discharges are well documented with antipsychotic drugs such as haloperidol and olanzapine.

However, data regarding the potential risk of EEG alterations with quetiapine, a new antipsychotic, is limited. In a retrospective analysis, Dr. Benedikt L. Amann and colleagues of the Department of Psychiatry, Section of Clinical Neurophysiology, University of Munich, reviewed EEG recordings from 81 patients treated either with the atypical antipsychotics quetiapine and olanzapine or the typical antipsychotic haloperidol, and compared the data with that of 30 healthy subjects.

Diagnoses according to the Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV included 61 patients with schizophrenia, 9 with brief psychotic disorder, 8 with schizoaffective disorder, and 3 with delusional disorder. With the exception of 6 patients receiving co-medication with nonbenzodiazepine hypnotics, all were under stable monotherapy with 22 patients taking quetiapine, 37 taking olanzapine, and 22 taking haloperidol.

Patients were grouped according to antipsychotic treatment, and compared with a control group of healthy subjects matched for age and gender. No significant differences regarding demographic characteristics existed between the 4 groups.

EEGs were retrieved from a database and visually assessed independently by 3 experienced investigators, with 1 blinded regarding medication, dosage, and patient diagnosis. Findings were classified as normal or abnormal, with or without epileptiform activity.

Abnormal EEGs were observed in 5% of the quetiapine group, 35% of the olanzapine group, 23% of the haloperidol group, and 7% of controls.

The only group to demonstrate epileptiform activity was olanzapine patients (11%). Furthermore, EEG abnormalities increased significantly with dose in the olanzapine group, compared with patients treated with haloperidol, quetiapine, or controls.

Based on previous studies regarding receptor profiles of various antipsychotics, the researchers postulate that pharmacodynamic distinctions between the drugs might lead to different effects on brain electric activity.

Because the rate of EEG abnormalities observed with quetiapine was both low and comparable to healthy subjects, the researchers suggest that quetiapine might be an alternative for patients with the epilepsy or seizures with psychosis.

"Nevertheless, prospective studies are required to evaluate EEG abnormalities by antipsychotics and their clinical significance," they concluded.

The Stanley Medical Research Institute provided study funding.

Hum Psychopharmacol Clin Exp 2003;18:641-646. "EEG abnormalities associated with antipsychotics: a comparison of quetiapine, olanzapine, haloperidol and healthy subjects"

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