Epinephrine (also called adrenaline) and norepinephrine (also called noradrenaline) have a lot in common. Both are hormones that travel through your body, affecting many tissues and organs. Both also are neurotransmitters, which means they are chemical messengers that travel through your body's vast network of nerve cells, affecting everything from your heartbeat to your emotions.
Both are key players in your “fight-or-flight” response, which kicks in when you're under stress and your brain senses danger. And both are used, in certain situations, as medications.
While epinephrine and norepinephrine often work together, they're not the same thing. They play different roles and have different uses in medicine.
Catecholamines
Norepinephrine and epinephrine are part of a group of hormones known as catecholamines. These hormones are released by your adrenal glands, which sit above your kidneys. In some cases, they also are released from the brain as neurotransmitters.
The other major member of the group is dopamine. As a hormone, dopamine joins norepinephrine and epinephrine in boosting the fight-or-flight response. Dopamine plays a bigger role as a neurotransmitter, affecting movement, memory, pleasure, attention, and sleep.
Levels of all three hormones rise when you are in a stressful situation. When levels are high, your body responds, in part, by increasing:
- Blood flow to your muscles and brain
- Alertness
- Heart rate
- Blood pressure
If you have lasting symptoms such as hard-to-treat high blood pressure, anxiety, nausea, and severe headaches, your doctor might test your blood and urine for catecholamine levels. High levels can be linked to rare adrenal gland tumors.
Function of Norepinephrine vs. Epinephrine
While norepinephrine and epinephrine are both hormones and neurotransmitters, they have different roles in your body.
Norepinephrine function
Norepinephrine works most often as a neurotransmitter, sending messages from your brain, through your spinal cord, to other areas of your body. It's at work in your body all the time, not just when you're under stress. Here are some of the ways norepinephrine works:
Fight or flight. When you are under stress, norepinephrine works with epinephrine to reach multiple organs and tissues and tell them how to respond to the perceived threat. This makes your pupils get bigger so you see more light. It makes your skin pale because it sends blood away from the skin to your muscles. It makes your heart pump faster, speeds up your breathing, and gets more glucose (sugar) into your bloodstream to give you more energy.
Blood pressure. Norepinephrine plays an important role in regulating blood pressure, keeping it from getting too low in a crisis by narrowing your blood vessels. But if your norepinephrine levels are consistently too high, you can develop high blood pressure.
Biorhythms. Norepinephrine works to maintain your sleep-wake cycles. It helps you wake up in the morning, improves your attention, and helps you focus throughout the day. Any time you stand up and move around, your body is likely to respond by pumping out some norepinephrine to help you get active and stay alert.
Emotions. Low levels can contribute to depression and other mental health problems. Bursts of norepinephrine can make you feel very happy but are also linked to panic attacks.
Epinephrine function
Epinephrine is adrenaline. It most often acts as a hormone released from the adrenal glands in response to stress. It has a smaller role as a neurotransmitter. During the fight-or-flight response, epinephrine:
- Works with norepinephrine to increase your heart rate, blood pressure, and energy
- Decreases your ability to feel pain — something that might help you keep running or fighting despite an injury
- Temporarily boosts strength
Having too much adrenaline in your system due to stress can make you feel restless and irritable, cause insomnia, and even damage your heart.
Treatment With Norepinephrine vs. Epinephrine
Because norepinephrine and epinephrine can have big, fast-acting effects on your body, doctors have learned to use them as medicines. Each has some important uses.
Norepinephrine treatment
Norepinephrine is used as a medicine to increase and maintain blood pressure in short-term situations where blood pressure can get too low. These include:
- Cardiac arrest (when your heart suddenly stops working)
- Septic shock, a life-threatening condition that can follow an infection
- Blood transfusions
- Spinal anesthesia
- Drug reactions
- Neurogenic shock, a life-threatening condition caused by spinal cord injury
- Pericardial tamponade, in which extra fluid builds up in the space around your heart.
- Dangerously low blood pressure from any cause
In addition, stimulant and non-stimulant drugs for attention deficit hyperactivity disorder (ADHD) work largely by increasing norepinephrine levels in your brain. So do some antidepressants.
To get some of the mood and attention-boosting effects of increased norepinephrine without taking medicine, you can try:
- Exercising
- Getting better sleep
- Listening to music
- Meditating
- Eating chocolate (high in dopamine, which produces norepinephrine)
Epinephrine treatment
As a medicine, lab-made epinephrine is used in many different situations, including:
- Cardiopulmonary resuscitation (CPR), to stimulate your heart
- Eye surgery, to keep your pupils dilated (opened wide)
- Septic shock, to increase blood pressure
- Asthma, to open airways and reduce spasms
When used to treat asthma, epinephrine is given as an inhaled mist.
Epinephrine for anaphylaxis
One of epinephrine's most important uses is as an emergency treatment for life-threatening allergic reactions, or anaphylaxis. The medicine is given with an auto-injector pen or as a nasal spray and is available by prescription. If you have severe allergies, your doctor may recommend you carry epinephrine or have it nearby at all times.
Some symptoms of anaphylaxis include:
- Swelling or tightening of the throat
- Difficulty breathing
- Shortness of breath
- Wheezing or coughing
- Lightheadedness or fainting
Your doctor will tell you how to use the medicine. In some cases, people with known severe allergies take it before symptoms start. This happens when they're exposed to something that can cause an extreme reaction, such as certain foods or a bee sting. In other cases, it's taken when symptoms start. It can quickly reverse life-threatening symptoms such as a blocked airway. Sometimes people need more than one dose.
You may not need emergency medical care after using epinephrine for anaphylaxis if you recover quickly and fully and have a second dose on hand. But call 911 if:
- Your reaction is severe
- Your symptoms don't get better quickly and completely or nearly completely
- Your symptoms come back or get worse
Norepinephrine vs. Epinephrine Deficiency Symptoms
It's possible for your body to make too little norepinephrine or epinephrine. The causes can be complex since norepinephrine and epinephrine are part of a system that involves multiple organs, nerves, and other hormones and neurotransmitters.
Conditions tied to low levels of norepinephrine include:
- Anxiety
- Depression
- ADHD
- Headaches
- Poor memory
- Poor sleep
- Low blood pressure (hypotension)
- Low blood sugar (hypoglycemia)
- Dopamine beta-hydroxylase deficiency — a rare genetic condition that causes chronic low blood pressure, drooping eyelids, and other problems
Problems associated with low levels of epinephrine include:
- Anxiety
- Depression
- Headaches
- Sleep problems
- Low blood sugar (hypoglycemia)
Takeaways
Any time you face a real threat that requires quick reactions, both norepinephrine and epinephrine are your friends. These hormones and neurotransmitters play key roles in your fight-or-flight response. But they have different functions in your body and play different roles when used as medicines. Norepinephrine is especially important as a medicine to raise blood pressure when it's too low, while epinephrine is used to reverse severe allergic reactions.
Norepinephrine vs. Epinephrine FAQs
Does norepinephrine have side effects?
Yes, if you get norepinephrine as an injected medicine, you could have an allergic reaction, trouble breathing, irregular heartbeats, or chest pain.
Does epinephrine have side effects?
Yes, if you take it as an inhaled mist for asthma, you can get breathing problems, a fast heartbeat, chest pain, and other problems. If you inject it or inhale it in a nasal spray, you can get other side effects, such as pain, tingling, or numbness in your hands or feet.
