Phenytoin and cognitive function: effects on normal volunteers and implications for epilepsy

Br J Clin Psychol. 1981 Sep;20(3):155-62. doi: 10.1111/j.2044-8260.1981.tb00513.x.


Despite the widespread use of phenytoin in the treatment of epilepsy, few studies have examined its effects on cognitive functioning. We report here the results of an investigation into the effects of phenytoin on the performance of non-epileptic volunteers, on a series of specially designed psychological tests. Subjects received placebo or phenytoin 300 mg per day for two weeks in a double-blind crossover design and measures were taken of phenytoin serum levels. The results demonstrate a deleterious effect of phenytoin upon several important aspects of cognition, including memory, concentration, mental and motor speed. The implications of our findings for the treatment of patients with epilepsy are discussed.

Publication types

  • Clinical Trial
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Attention / drug effects
  • Cognition / drug effects*
  • Decision Making / drug effects
  • Epilepsy / drug therapy*
  • Humans
  • Male
  • Memory / drug effects
  • Motor Skills / drug effects
  • Phenytoin / adverse effects*
  • Phenytoin / therapeutic use
  • Visual Perception / drug effects


  • Phenytoin