Pronunciation: (ep"u-nef'rin, -rēn),[key] —n. 1. Biochem.a hormone secreted by the adrenal medulla upon stimulation by the central nervous system in response to stress, as anger or fear, and acting to increase heart rate, blood pressure, cardiac output, and carbohydrate metabolism.
2. Pharm.a commercial form of this substance, extracted from the adrenal glands of sheep and cattle, or synthesized: used chiefly as a heart stimulant, to constrict the blood vessels, and to relax the bronchi in asthma. Also,ep"i•neph'rin.Also called adrenaline.