Adrenaline (ball and stick models) and blood cells, illustration. Adrenaline, or epinephrine, is a hormone secreted by the adrenal glands. It plays a central role in the stress response. When released into the bloodstream, adrenaline acts to increase the heart rate and blood pressure, dilate the pupils, elevate blood sugar levels and redistribute blood to the muscles. As a drug it is used to stimulate cardiac action in cardiac arrest, as a vasoconstrictor in anaphylactic shock and sepsis, and as a bronchodilator in acute bronchial asthma.