vasoconstrictor /-kənstrik″tər/ [L, vas + constrigere] , 1. adj., pertaining to a process, condition, or substance that causes the constriction of blood vessels. 2. n., an agent that promotes vasoconstriction. Cold, fear, stress, and nicotine are common exogenous vasoconstrictors. Internally secreted epinephrine and norepinephrine cause blood vessels to contract by stimulating alpha-adrenergic receptors on the vascular smooth muscle. Other endogenous vasoconstrictors are angiotensin, which is formed in the blood through the action of renin, and antidiuretic hormone, which is secreted by the pituitary. Alpha-adrenergic sympathomimetic drugs also cause vasoconstriction, and several of these agents are used for this action in maintaining blood pressure during anesthesia and in treating pronounced hypotension resulting from hemorrhage, myocardial infarction, septicemia, sympathectomy, or drug reactions. Also called vasopressor. Kinds include phenylephrine hydrochloride, metaraminol bitartrate, norepinephrine.
