Epinephrine, << ehp uh NEHF rihn, >> is a hormone secreted by the adrenal glands. It is also called adrenalin. Epinephrine is sometimes spelled epinephrin, and adrenalin is sometimes spelled adrenaline.
Epinephrine helps the body adjust to sudden stress. When a person becomes angry or frightened, the adrenal glands release large amounts of epinephrine into the blood. The hormone causes changes in the body to make it more efficient for “fight or flight.” For example, epinephrine increases the strength and rate of the heartbeat and raises the blood pressure. In addition, epinephrine speeds up the conversion of glycogen into glucose, which provides energy to the muscles.
Epinephrine can be extracted from the adrenal glands of animals or it can be chemically synthesized. The drug stimulates the heart and relaxes muscles in the bronchioles, the small air passages in the lungs. Doctors use epinephrine to treat severe allergic reactions and to restore the heartbeat in patients who are suffering cardiac arrest. Epinephrine was once widely used to treat asthma attacks, but doctors now usually treat asthma with drugs that do not excite the heart.
