Epinephrine

Epinephrine, also known as adrenaline, is a hormone and a medication. The names "adrenaline" and "epinephrine" come from the Latin words ad-+renes and the Greek words epi-+nephros. Both mean "into or onto the kidney" (adrenaline is made in the adrenal glands, which sit on top of the kidneys). In medical jargon, epinephrine is shortened to just "epi" (pronounced eh-pee).
History
The hormone was first isolated and purified in 1901 by Japanese chemist Jokichi Takamine. It was patented in the United States with the name "adrenaline."
Effects in the body
Epinephrine is one of two chemical messengers that control the sympathetic nervous system and cause the "fight or flight" response. Epinephrine makes the "fight or flight" response kick in, and causes changes in every part of the body. For example, it:
Makes the heart beat faster
Increases blood pressure
Causes vasoconstriction (it makes the blood vessels narrower, which sends extra blood to the most important organs in the body, like the heart, lungs, and brain)
Causes bronchodilation (it makes the bronchi, the tubes that bring air to the lungs, get wider, so more air can get into the lungs)
Adverse effects
Because epinephrine causes so many changes in the body, it can cause changes that make a person feel bad. Sometimes, it can cause changes that could be dangerous. These are called adverse effects. They include:
Tachycardia (a fast heart rate) or heart palpitations (feeling the heart pounding inside the chest), because epinephrine makes the heart beat harder and faster
Hypertension (high blood pressure), because epinephrine raises blood pressure
Cardiac arrhythmia (where the heart beats in a way that is not normal)
Anxiety or panic attack
Tremor
Acute pulmonary edema (fluid in the lungs)
Medical uses
Epinephrine is used to treat a few different medical problems.
Cardiac arrest
Epinephrine can restart a person's heart when they are in cardiac arrest (their heart has stopped beating). It can make the heart start pumping blood to the rest of the body again.
Anaphylaxis
Epinephrine is the best medicine to treat anaphylaxis, which is a very bad allergic reaction. During anaphylaxis, the bronchi (which bring air to the lungs) get narrower and narrower until the person cannot breathe. Epinephrine makes the bronchi get wider so air can get into the lungs and the person can breathe again. It also treats some of the other symptoms of anaphylaxis.
People with allergies can get a doctor's prescription for an epinephrine "auto-injector." Anyone can learn to use an auto-injector. If a person starts having anaphylaxis, they just press the auto-injector to the outside of their thigh, and the device will automatically inject the right dose of epinephrine into the person's thigh.
Asthma
Epinephrine can be given for asthma attacks, if regular asthma medications like albuterol do not work. The epinephrine will relax the muscles around the lungs and widen the bronchi, making it easier to breathe.
Croup
Croup is a disease that mostly happens in children, and is caused by a virus. It can cause swelling in the throat, which can make it hard to breathe. Epinephrine can help bring this swelling down, which makes it easier for the child to breathe. Epinephrine works best for croup if it is breathed in, so it is made into a special mist that can be inhaled.