Norepinephrinebitartrate is a precursor of epinephrine. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus.
Isoproterenol bitartrate is a beta-sympathomimetic and an isopropyl analog of Epinephrine, which acts on the heart, bronchi, skeletal muscle, and alimentary tract. It is used mainly as a bronchodilator and heart stimulant.