Hemodynamic effects of high dosages of verapamil and the lack of protection by 4-aminopyridine in the rabbit.

4-Aminopyridine (1 mg/kg) restored a 35% fall in arterial blood pressure in rabbits evoked by a verapamil infusion (0.5 mg/kg/min) more effectively than calcium-levulate (approx. 13 mg/kg). However, the lethal dose of verapamil for rabbits (mean: 7.1 mg/kg given by intravenous infusion in 14.3 min) was not affected by 4-aminopyridine pretreatment.