antiadrenergic /an′ti·ad′rənur″jik, an′tī-/ [Gk, anti + L, ad + ren, to kidney] , 1. pertaining to the blockage of the effects of impulses transmitted by the adrenergic postganglionic fibers of the sympathetic nervous system. 2. an antiadrenergic agent. These drugs block the response to norepinephrine bound to alpha receptors and reduce the tonus of smooth muscle in peripheral blood vessels, causing increased peripheral circulation and decreased blood pressure. Alpha1-blocking agents include ergotamine derivatives, phenoxybenzamine, phentolamine, and tolazoline hydrochloride; they are used to treat conditions such as migraines, Raynaud’s disease, pheochromocytoma, diabetic gangrene, and spastic vascular disease. Beta1-blocking agents decrease the rate and force of heart contractions and are administered for hypertension, angina, and arrhythmias; propranolol hydrochloride and its congeners are examples. Also called sympatholytic, sympatholytic agent. Compare adrenergic, anticholinergic.
