Effects of adrenergic blockade on plasma catecholamine levels during adrenaline infusion.

Alpha and beta adrenergic blocking drugs were administered, either singly or in combination, prior to a 3hr adrenaline infusion (2 microgram kg body wt-1 min-1)), Animals were premediated with either phenoxybenzamine (1 mg kg body wt-1 min-1). Phenoxybenzamine did not affect circulating adrenaline levels, but propranolol, either alone or in combination with phenoxybenzamine, resulted in a significant reduction in plasma adrenaline levels when compared with the control unblocked situation of adrenaline infusion without premedication. The results provide a possible explanation for the protective effect of combined adrenergic blockade in shock situations.