Epinephrine
A non-selective alpha and beta agonist given by injection for anaphylaxis, cardiac arrest and the low blood pressure of septic shock.
Also called adrenaline (UK and European name).
Drug card
- Class
- Sympathomimetic
- How it works
- Activating alpha and beta receptors, so vessels constrict and airways open
- Used for
- Anaphylaxis and severe allergic reactions
- Cardiac arrest
- Low blood pressure in septic shock
- Keeping the pupil dilated during eye surgery
- Known for
- Fast heart rate and palpitations
- Ventricular arrhythmias, including fibrillation
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does epinephrine work?
The adrenal hormone, acting on alpha and beta adrenergic receptors. Through alpha-1 it constricts vessels and reverses the leaky vasodilation of anaphylaxis; through beta-1 it makes the heart beat faster and harder; through beta-2 it relaxes bronchial smooth muscle. Beta effects dominate at low doses and alpha effects at high doses.
Like other sympathomimetics: They activate adrenergic receptors, copying the norepinephrine and epinephrine of the sympathetic nervous system. Alpha-1 activation constricts blood vessels, beta-1 activation makes the heart beat faster and harder, and beta-2 activation relaxes bronchial and some vascular smooth muscle. Each drug's mix of receptors decides its use, and the catecholamines here are given by injection or infusion and act briefly.
Uses
What is epinephrine used for?
- Anaphylaxis and severe allergic reactions
- Cardiac arrest
- Low blood pressure in septic shock
- Keeping the pupil dilated during eye surgery
Side effects
Side effects of epinephrine
- Fast heart rate and palpitationsKnown for
- Ventricular arrhythmias, including fibrillationKnown forSerious
- Sharp rise in blood pressure, risking a brain bleedSerious
- Angina or heart attackSerious
- Anxiety, fear and restlessness
- Tremor
- Headache
- Pallor and cold hands and feet
- High blood sugar
- Low potassium
- Tissue necrosis where it leaks or is injected repeatedlySerious
- Breathing difficulty and pulmonary edemaSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Beta blockers, tricyclics and MAOIs boost its pressor effect; halothane-type anesthetics raise the risk of arrhythmia.
- Heart disease, hypertension or hyperthyroidism raise the risk of harm but do not rule it out in anaphylaxis.
- For anaphylaxis it is injected into the outer thigh muscle, not the buttock, fingers, hands or feet.
- It is not used for hypotension caused by phenothiazines, as blood pressure can fall further.
Good to know: Its beta-2 action, which norepinephrine largely lacks, opens the airways and makes it the emergency drug for anaphylaxis.
Remember it
A way to remember it
Norepinephrine squeezes, dobutamine pumps, epinephrine does both and opens the airways.
Norepinephrine acts mostly on alpha-1 receptors and constricts vessels; dobutamine acts mostly on beta-1 receptors and strengthens the heartbeat; epinephrine acts on alpha and beta receptors, and its beta-2 action relaxes the airways, which is why it is used in anaphylaxis.
Written for biofideX
Its class
Sympathomimetics
Other sympathomimetics with a card:
Easily mixed up with beta blockers, alpha-1 blockers and short-acting beta-2 agonists.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Epinephrine injection 1 mg/mL: label (DailyMed)
- Adrenaline 1 mg/10 ml (1:10,000) pre-filled syringe: SmPC (emc)
- Epinephrine hydrochloride (NCI Thesaurus)
- Epinephrine (NCI Thesaurus)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Autonomic nervous system
Epinephrine is one of 10 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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