Epileptiform seizures in domestic fowl. VI. Plasma phenobarbital concentrations and anticonvulsant activity

The relationship between plasma phenobarbital concentrations and anticonvulsant activity was determined against seizures induced in epileptic chickens by intermittent photic stimulation (IPS). Intraperitoneally administered phenobarbital produced a plasma-concentration-dependent reduction in both the incidence and severity of seizures. Complete protection against IPS-induced seizures was observed for a period of 6 h after acute phenobarbital administration during which the mean plasma phenobarbital concentrations were between 16.2 +/- 0.91 and 13.6 +/- 1.0 microgram/lm. Plasma phenobarbital concentrations below 3.6 +/- 0.06 microgram/ml had no measurable effect.