Epileptiform seizures in domestic fowl. VII. Plasma phenytoin concentrations and anticonvulsant activity.

Acute dose-response studies with phenytoin were conducted to determine the relationship between plasma levels and anticonvulsant effect in epileptic chickens. Phenytoin produced statistically significant reductions in both the incidence and severity of seizures in photosensitive epileptic chickens when the plasma concentrations exceeded 8.15 +/- 0.89 microgram/ml. A high correlation exists between plasma phenytoin concentrations and both the reduction in incidence or severity of seizures. However, the appearance of plasma concentration dependent neurological toxicities resulted in a failure to achieve complete protection against intermittent photic stimulation induced seizures.