Why should you be careful to use haloperidol in patients with epileptic seizures?/nAre there any kn

Fråga: Why should you be careful to use haloperidol in patients with epileptic seizures?

Are there any known interactions between haloperidol and phenytoin?

The question concerns a 70-year-old woman with an earlier myocardial infarction, a cerebral infarct and secondary to that epileptic seizures. She now suffers from psychotic symptoms and antipsychotic therapy is indicated.

Sammanfattning: Haloperidol as other neuroleptics reduces the seizure threshold and may aggravate any type of seizure in epileptic patients, but haloperidol appears to be one of the agents with the fewest epileptogenic effects.

No information about an interaction between haloperidol and phenytoin has been found.

Svar: Antipsychotic medications are known to lower the seizure threshold, and seizures associated with antipsychotic therapy occur in approximately one per cent of patients receiving these medications. Seizure activity has been associated with antipsychotic use even at usual therapeutic doses. Antipsychotic medications seem to produce EEG abnormalities in treated patients and in normal control subjects and also tend to potentiate any type of seizures in epileptic patients (1). The cholinergic/dopaminergic balance in the brain may play an important role in seizure production in patients treated with antipsychotic medications. However, the results are conflicting since some data suggest that anticholinergic effects may protect against the occurrence of seizures while other data suggest that it may cause seizures in epileptic patients (1,2).

There are no good studies available comparing the ability of different antipsychotic drugs to induce seizures, but seizure production during antipsychotic therapy has been most frequently reported with chlorpromazine and promazine, while for example tioridazine and haloperidol appear to be agents with fewer epileptogenic effects (1,3). General recommendations in predisposed patients include avoiding high doses, polypharmacy and making gradual adjustments of the dose (1,4).

Any possible interaction between haloperidol and phenytoin has not been found in current handbooks or Medline and Drugline. 1 Cold JA, Wells BG, Froemming JH: Seizure activity associated with antipsychotic therapy. DICP Ann Pharmacother 1990; 24: 601-606 2 Barnes T: Antipsychotic drugs and their side-effects. 1993; page 216-217 3 Drugline nr 07882 (year 1991) 4 Ojemann LM, Baugh-Bookman C, Dudley DL: Effect of psychotropic medications on seizure control in patients with epilepsy. Neurology 1987; 37: 1525-1527