Seizures in brain tumour patients are common; therefore, most of the brain tumour patients require chronic treatment with antiepileptic drugs (AED). Also acute, and in some instances prophylactic, treatment may be necessary. Many AED either induce (mainly CYP3A4) or inhibit liver enzymes, and therefore affect the metabolism of drugs, such as chemotherapeutic agents or steroids. Chemotherapeutic agents, metabolized by CYP3A4 system are affected by enzyme-inducing AED (EIAED), are discussed.