In areas where blood supply is poor, it can be dangerous to include adrenaline in the injection, as necrosis of the tissues may ensue. These areas include the extremities such as the fingers and toes. Adrenaline can be replaced by other vasoconstrictors, such as the polypeptide felypressin. Felypressin, which is related to antidiuretic hormone, has the advantage of causing fewer cardiac problems.