Epinephrine and norepinephrine belong to the same class of catecholamines, but the difference in chemical structure is that norepinephrine does not have a methyl group on the N-atom, which leads to the difference in pharmacological effects between the two.
Norepinephrine agonizes the α-receptors with strong effects, is not selective for α1 and α2, and has weak effects on cardiac β1 receptors, mainly causing vascular smooth muscle contraction, which is most obvious in skin and mucous membranes, followed by renal blood vessels, and increases blood pressure.
Epinephrine is an α and β receptor agonist, which can act on α1 receptors in vascular smooth muscle to cause vasoconstriction (mainly in skin, mucous membranes, and renal blood vessels); it can also agonize β2 receptors to cause vasodilatation (mainly in skeletal muscle, liver, and coronary blood vessels); and it can also act on the β receptors in the myocardium, sinoatrial node, and the conduction system to enhance myocardial contraction, increase heart rate, accelerate conduction, and enhance cardiac output.
Epinephrine and norepinephrine should be used under medical supervision.