DUAL ADRENERGIC BLOCKADE AND EPINEPHRINE INFUSION

¹ University of Tennessee Medical Units, Department of Pharmacology, Memphis, Tennessee

The effects of alpha, beta and dual adrenergic blockade on toxic amounts of epinephrine were studied in anesthetized dogs receiving a 2-hr. i.v. infusion of epinephrine (10 µg/kg/min). Dual blockade by phenoxybenzamine (7.5 mg/kg) and propranolol (2 mg/kg) nearly eliminated blood pressure alterations by epinephrine. As the dose of phenoxybenzamine was reduced in combination with propranolol (2 mg/kg), the pressor response to epinephrine progressively increased. The myocardial hemorrhage produced by epinephrine alone was increased by propranolol, unchanged or slightly reduced by phenoxybenzamine and eliminated by dual adrenergic blockade. The epinephrine-induced effects of pericardial effusion, cardiac arrhythmias, electrocardiogram voltage depression, acidemia and death could all be prevented by adequate dual adrenergic blockade without complete loss of pressor response.