This document summarizes vasoconstrictors which are drugs that constrict blood vessels and control tissue perfusion. It is added to local anesthetics (LA) to oppose their vasodilatory effects. Vasoconstrictors are classified as catecholamines like epinephrine and norepinephrine or noncatecholamines. They can act directly, indirectly, or mixed on receptors like alpha, beta 1,2,3 receptors. The maximum recommended doses for epinephrine are provided for healthy and cardiac patients. Dilutions of vasoconstrictors from 1:1000 to 1:200,000 are explained. The document also compares epinephrine and norepinephrine.