Epinephrine is an adrenergic substance with mixed alpha and beta effects. Clinically, it can reproduce all of signs and symptoms of sympathetic nervous system activation, such as tachycardia, arrhythmias, hypertension, bronchodilation, vasoconstriction, mydriasis, hyperglycemia, lactic acidosis, and increased cardiac contractility. Since it is a catecholamine, epinephrine is not effective orally but may be given intravenously or subcutaneously.
For cardiac resuscitation, a 1mg dose is administered intravenously during CPR, and repeated every 5 minutes. Here, epinephrine is used for the alpha effect (vasoconstriction) to maintain aortic blood pressure and coronary artery perfusion pressure during CPR.
Epinephrine is the drug of choice for anaphylaxis because of its ability to counteract vasodilation and maintain blood pressure (alpha mediated vasoconstriction effect), bronchodilate (beta2 effect), increase cardiac output (beta1 effect) and decrease mediator release and edema.
Lidocaine (a local anesthetic) can be combined with low dose epinephrine for local anesthesia where vasoconstriction can help to decrease bleeding.