Epinephrine, also known as adrenaline, is a hormone that increases heart rate, tightens the blood vessels, and opens the airways. Epinephrine is the best treatment for anaphylaxis. It is most effective when given immediately, and any delay in administration decreases the effectiveness. Epinephrine is injected intramuscularly in the med-thigh area. The most common method of delivery is an auto-injector, device with spring loaded needle which deliveries a preset dose. Popular brands are EpiPen, Twinject, Adrenaclick, Anapen and Auvi-Q.