What Is Epinephrine?

A quick inside tip on field instructors; we all have our favorite questions to ask new riders. Those questions that help us get a more firm understanding of where our students knowledge base rests. What kind of practical knowledge are they carrying out into the field? Some of them are fair questions. Some of them aren’t. That’s life.

One of my favorite questions to ask that new rider early in the ride along is, “So what is epinephrine anyway?” (For the record, this is an extremely fair question.) I’ve found this to be a telling conversation because the scope of the question gives the student a lot of rope. This is a question where the student can choose to be shockingly simple or impressively complex. The choice is theirs.

I ask this question regardless of the students experience or training. I’ve had brand new EMT students knock the question out of the park and I’ve had experienced paramedics strike out miserably. All baseball metaphors aside, it’s a telling question. It speaks to a care givers understanding of the drugs we are able to administer. (Yes, all of us.) It’s revealing about ones understanding of the autonomic nervous system and it exposes an individuals understanding of basic pathophysiology.

When I ask the question, the answer I’m looking for is something like this:

Epinephrine is the primary


of the sympathetic nervous system.

Ok … ok, I feel you reaching for the mouse. Don’t click away just yet. Give me a chance to break it down. It isn’t nearly as complicated as it sounds.


Is also known more commonly as adrenaline. But don’t get any funny ideas. I think the worst answer to the, “What is Epinephrine?” question is, “Uh … well … it’s adrenaline.” OK great. I think I remember my second grade teacher saying something about not using a word to define a word. But OK, yes. Epinephrine is indeed adrenaline. For bonus points you can point out that epinephrine is a hormone excreted by the adrenal gland.

is the primary

There are two chemicals that are excreted by the body to stimulate the sympathetic nervous system. They are epinephrine and norepinephrine. Of the two, epinephrine is more plentiful. (Epi is systemic, norepinephrine is created at the sympathetic ganglia.) That’s why we refer to epinephrine as the primary neurotransmitter.


A neurotransmitter is simply a chemical that your body excretes to make a nerve fiber work. All along the highway of your nervous system are synapse sites, spread out like toll booths. They regulate the electrical impulses traveling through the system. Impulses need a neurotransmitter to pass through the tollbooth and continue on their merry way. No neurotransmitter, no signal. Neurotransmitters are chemicals that make your nerve fiber work.

of the sympathetic nervous system

The autonomic nervous system (the one that regulates all of those involuntary body responses) is divided into two halves. They are the sympathetic and the parasympathetic systems. The sympathetic system is sometimes called the “fight or flight” system. This system ramps your body up for activity. The parasympathetic system is also known as the “feed or breed” system. This system prepares your body to refuel or reproduce. The two systems work in opposition to each other. They create a balance of body function appropriate to your surroundings and activities. Picture two children rocking on a teeter totter. This is the back and forth balance of the autonomic nervous system.

Let’s take a quick look at the physical effects of stimulating each half of the autonomic system.

So epinephrine is the chemical that makes that sympathetic half of the system work. The actions of the sympathetic nervous system and the actions of epinephrine are the same. Often I find that students, when asked to name the actions of the drug epinephrine think back to their pharmacology lecture and recall one or two actions for the drug. But when I ask the actions of the sympathetic nervous system they can recite the whole shebang. (Well, most of the shebang.)

They are one and the same. And remember, the next time someone asks you, “What is epinephrine?” you know what to say. (If you need a hint: it’s up above in red.) And then dare them to ask you to explain further.