Fluanisone, a butyrophenone derivative, is a neuroleptic agent, which was used in the treatment of schizophrenia and mania. Veterinary formulation fentanyl/fluanisone (Hypnorm) is used for rodent analgesia during short surgical procedures. Hypnorm is a combination often used as a neuroleptanalgesic and anaesthetic. Fentanyl-fluanisone has stimulating effects on the amount of spike-wave discharges, but not in a dose-dependent manner. A low dose of 0.01 mg/kg fentanyl with 0.5 mg/kg fluanisone causes a large increase in epileptic activity. This effect is larger than with a middle dose of 0.1 mg/kg fentanyl and 5 mg/kg fluanisone and much larger than with a high dose of 0.2 mg/kg fentanyl with 10 mg/kg fluanisone. The last two doses cause a prolonged anaesthetic state in rats. Fluanisone alone in the same doses as in the mixture induces a large dose-dependent increase in spike-wave activity, with only a small effect on spike frequency. This might be caused by the antagonistic action of this drug at dopamine receptors.