Norepinephrine
A catecholamine vasopressor acting mainly on alpha-1 and beta-1 receptors, infused to raise blood pressure in shock.
Also called noradrenaline (UK and European name) or levarterenol (older name).
Drug card
- Class
- Sympathomimetic
- How it works
- Activating alpha-1 receptors to constrict vessels, with some beta-1 action
- Used for
- Acute low blood pressure, as in septic shock
- Cardiac arrest with profound hypotension (adjunct)
- Known for
- High blood pressure
- Slow heart rate (reflex)
- Tissue necrosis if the infusion leaks
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does norepinephrine work?
The sympathetic neurotransmitter, given by infusion. Alpha-1 activation constricts arteries and veins, and beta-1 activation strengthens the heartbeat. Resistance and blood pressure rise, and the reflex vagal response often slows the heart, so cardiac output changes little. Its effect ends within a minute or two once the infusion stops.
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 norepinephrine used for?
- Acute low blood pressure, as in septic shock
- Cardiac arrest with profound hypotension (adjunct)
Side effects
Side effects of norepinephrine
- High blood pressureKnown forSerious
- Slow heart rate (reflex)Known for
- Tissue necrosis if the infusion leaksKnown forSerious
- ArrhythmiasSerious
- Ischemia and gangrene of the limbsSerious
- Less blood flow to the kidneys and less urineSerious
- Lactic acidosis from poor tissue perfusionSerious
- Anxiety
- Headache
- Breathing difficulty and pulmonary edemaSerious
- Marked low blood pressure if stopped abruptlySerious
- Higher blood sugar
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Hypovolemia is corrected first; otherwise vessels clamp down and organs stay underperfused despite a normal pressure.
- Given into a large vein; extravasation is treated by infiltrating phentolamine.
- MAOIs, including linezolid, and tricyclic antidepressants can cause severe, prolonged hypertension.
- Avoided in mesenteric or peripheral vascular thrombosis, where it can extend the ischemia.
Good to know: Mainly a vasoconstrictor: it has little beta-2 action, unlike epinephrine, and reflex slowing means it raises pressure more than cardiac output.
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:
- Norepinephrine bitartrate in dextrose injection: label (DailyMed)
- Norepinephrine bitartrate injection: label (DailyMed)
- Norepinephrine bitartrate (NCI Thesaurus)
- Norepinephrine, DL- (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
Norepinephrine 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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