Epinephrine and norepinephrine are two neurotransmitters that also serve as hormones, and they belong to a class of compounds known as catecholamines. As hormones, they influence different parts of your body and stimulate your central nervous system. Having too much or too little of either of them can have noticeable effects on your health.

Chemically, epinephrine and norepinephrine are very similar. However, epinephrine works on both alpha and beta receptors, while norepinephrine only works on alpha receptors. Alpha receptors are only found in the arteries. Beta receptors are in the heart, lungs, and arteries of skeletal muscles. It’s this distinction that causes epinephrine and norepinephrine to have slightly different functions.

Epinephrine

Epinephrine, also called adrenaline, has powerful effects on the body. These include:

  • increased blood sugar levels
  • increased heart rate
  • increased contractility (how hard the heart squeezes)
  • relaxation of smooth muscle in the airways to improve breathing

These effects are designed to provide your body with extra energy. When you’re very stressed or afraid, your body releases a flood of epinephrine. This is known as the fight-or-flight response, or adrenaline rush.

Norepinephrine

Norepinephrine, also called noradrenaline, has effects similar to those of epinephrine, such as:

  • increased blood sugar levels
  • increased heart rate
  • increased contractility

Norepinephrine can also cause your blood vessels to narrow, which increases blood pressure.

The main difference

Both epinephrine and norepinephrine can affect your heart, blood sugar levels, and blood vessels. However, norepinephrine can also make your blood vessels become narrower, increasing blood pressure.

Epinephrine

In addition to being a hormone and neurotransmitter, epinephrine is also used as a medical treatment in its synthetic form.

Its main use involves the treatment of anaphylaxis. This is a severe allergic reaction that can affect a person’s breathing. An injection of epinephrine can help to open up your airway so you can breathe.

Other uses of epinephrine include:

  • Asthma attacks. An inhaled form of epinephrine can help treat or prevent severe asthma attacks.
  • Cardiac arrest. An epinephrine injection may restart your heart if your heart has stopped pumping (cardiac arrest).
  • Infection. If you have a severe infection and aren’t producing enough catecholamines, you may need to be given epinephrine through an intravenous line (IV).
  • Anesthesia. Adding epinephrine to local anesthetics can make them last longer.

Norepinephrine

Doctors sometimes use norepinephrine to treat septic shock, a severe infection that can lead to organ failure. This infection tends to cause dangerously low blood pressure. Norepinephrine given through an IV can help to constrict blood vessels, increasing blood pressure.

Although epinephrine can also be used for this purpose, norepinephrine is preferred due to its pure alpha receptor action.

Some people with ADHD or depression take medications that stimulate or increase the release of norepinephrine, including:

The main difference

Epinephrine is used to treat anaphylaxis, cardiac arrest, and severe asthma attacks. Norepinephrine, on the other hand, is used to treat dangerously low blood pressure. In addition, medications that increase norepinephrine can help with ADHD and depression.

Low levels of epinephrine and norepinephrine can contribute to a variety of physical and mental conditions, including:

  • anxiety
  • depression
  • fibromyalgia
  • hypoglycemia
  • migraine headaches
  • restless leg syndrome
  • sleep disorders

Chronic stress, poor nutrition, and taking certain medications, such as methylphenidate (Ritalin), can make your less sensitive to epinephrine and norepinephrine. These factors can also cause your body to start producing less epinephrine and norepinephrine.

Having too much adrenaline or norepinephrine can cause:

Some medical conditions cause people to have too much epinephrine, norepinephrine, or both. These include:

  • pheochromocytoma, a tumor that forms in your adrenal glands
  • paranganglioma, a tumor that forms on the outside of your adrenal glands
  • obesity

Ongoing stress can also cause high levels of both epinephrine and norepinephrine.

Epinephrine and norepinephrine are very similar neurotransmitters and hormones. While epinephrine has slightly more of an effect on your heart, norepinephrine has more of an effect on your blood vessels. Both play a role in your body’s natural fight-or-flight response to stress and have important medical uses as well.