Spectrum of EEG abnormalities during clozapine treatment

Beth A. Malow, Karen B. Reese, Susumu Sato, Phyllis J. Bogard, Anil K. Malhotra, Tung Ping Su, David Pickar

Research output: Contribution to journalArticlepeer-review


Clozapine is a novel antipsychotic agent effective in treating refractory schizophrenia. Clozapine produces fewer extrapyramidal effects than other neuroleptics, although agranulocytosis and seizures are significant adverse effects. To characterize the spectrum of clozapine-related electroenphalographic abnormalities, we identified 10 patients who had electroencephalograms (EEG) performed before and during clozapine treatment. These 10 patients represented a subset of individuals participating in an investigational trial. During clozapine treatment, five developed myoclonus and one experienced a generalized tonic-clonic seizure. Records were retrospectively reviewed by an electroencephalographer blinded to the patient's history and medications. All patients had normal EEGs before clozapine treatment. While receiving clozapine (250-900 mg daily), all patients developed background slowing in the theta and often delta ranges. Additionally, 7 patients exhibited bilateral spike, polyspike and slow wave discharges, one with a photoparoxysmal response. Follow-up EEGs performed in 4 of these 7 patients after a decrease in clozapine dosage and/or addition in valproic acid showed diminished epileptiform activity.

Original languageEnglish (US)
Pages (from-to)205-211
Number of pages7
JournalElectroencephalography and Clinical Neurophysiology
Issue number3
StatePublished - 1994
Externally publishedYes


  • Clozapine
  • EEG
  • Epileptiform abnormalities
  • Myoclonus

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)


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