Epinephrine (AKA adrenaline) is a non-selective adrenergic agonist.

What the heck does that even mean?

Let’s break this down.

• Adrenergic: The part of our neurological system that uses adrenaline and noradrenaline as the neurotransmitter. It’s like the words adrenaline and energy are smashed together… Get it? Adren +energ = energy from adrenaline AKA adrenergic.
• Agonist: A substance that attaches to a receptor to create a physiological response. So an antagonist BLOCKS the response and an agonist CREATES the response. I like to think about it like agonist is “A go” and antagonist is “Anti-go”.
• Nonselective: It doesn’t discriminate (completely) as to which receptor it likes to attach itself to. There are 2 main receptors the alpha receptors (alpha 1 & alpha 2) and the beta receptors (beta 1, beta 2, & beta 3).

So how do you know what it is going to select?

The answer is: by the route and by the concentration.

Route: IV versus IM

Concentration: 1:10,000 versus 1:1,000

• IV concentration is 1:10,000 and will have a greater affinity for alpha 1 thus vasoconstriction, meaning increased blood pressure and increased heart rate.
  • Give to someone in cardiac arrest.
  • Try to remember this by if someone is having a cardiac arrest 10,000 people will be coming to the patients’ room. (Rather than if someone would be having an anaphylactic reaction fewer people are needed)
  • Another way to remember this is that the concentration for IV is LESS potent (1/10,000 is a SMALLER fraction) and if you gave a stronger concentration you would probably over-excite their heart and vasculature.
• IM concentration is 1:1,000 and will have a greater affinity for Beta 2 thus smooth muscle relaxation and bronchodilation, meaning the airways that were just closing are now going to open up.
  • Give to someone having an anaphylactic reaction.
  • Try to remember this by if someone is having an anaphylactic reaction only 1,000 people will be coming to the patient’s room. (Rather than if they are having a cardiac arrest where more people are needed)
  • Another way to remember this is that the concentration for IM is MORE potent (1/1,000 is a LARGER fraction) and if you are giving it IM, you will need more for it to reach the veins as it absorbs.

If you are unsure, always ask! I carry a pocket guide called IV Therapy Notes, just in case I want to double check, or if I don’t know the answer.