Metoprolol
A cardioselective beta blocker used for high blood pressure, angina, heart failure and irregular heart rhythms.
Drug card
- Class
- Beta blocker
- How it works
- Blocking beta receptors, so the heart beats slower and less forcefully
- Used for
- High blood pressure
- Angina
- Heart failure, to cut deaths and hospital admissions
- Irregular heart rhythms such as atrial fibrillation
- Known for
- Slow heart rate (bradycardia)
- Hidden warning signs of low blood sugar
- Its name
- -olol means a beta blocker
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does metoprolol work?
Metoprolol blocks mainly β1 receptors, though at higher blood levels it blocks β2 as well. CYP2D6 metabolizes it, so poor metabolizers (about 8% of white people) and strong CYP2D6 inhibitors raise its levels several-fold or double them, which also erodes its cardioselectivity. It has no intrinsic sympathomimetic activity.
Like other beta blockers: They block β-adrenergic receptors, so epinephrine and norepinephrine act less: in the heart (β1) rate and force of contraction fall and AV conduction slows, and the kidneys release less renin. Cardioselective ones (atenolol, bisoprolol, metoprolol) act mainly on β1; non-selective ones also block β2 in airways and vessels; carvedilol and labetalol block α1 as well.
Uses
What is metoprolol used for?
- High blood pressure
- Angina
- Heart failure, to cut deaths and hospital admissions
- Irregular heart rhythms such as atrial fibrillation
- Migraine prevention
- Symptoms of an overactive thyroid
Side effects
Side effects of metoprolol
- Slow heart rate (bradycardia)Known for
- Hidden warning signs of low blood sugarKnown forSerious
- Tiredness
- Dizziness
- Depression
- Shortness of breath
- Low blood pressure
- Rash and itching
- Cold hands and feet
- Wheezing (bronchospasm)Serious
- Worsening heart failureSerious
- Angina or a heart attack if stopped suddenlySerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Strong CYP2D6 inhibitors such as fluoxetine, paroxetine, quinidine and propafenone double its levels.
- With digoxin, clonidine, diltiazem or verapamil, bradycardia is more likely.
- It can worsen the rebound hypertension that follows stopping clonidine.
- Taper over 1 to 2 weeks rather than stopping, above all in coronary disease.
Good to know: Its level depends on CYP2D6, so genes and interacting drugs make it vary more than most beta blockers' levels do.
Remember it
A way to remember it
One heart, two lungs: β1 for the heart, β2 for the lungs.
β1 receptors dominate in the heart and β2 receptors in the airways. Cardioselective beta blockers act mainly on β1, so they narrow the airways less than non-selective ones such as propranolol, though all need care in asthma.
A mnemonic widely used in teaching
Its name
-olol means beta blocker
Labetalol (-alol) and carvedilol (-dilol) are beta blockers that also block alpha-1 receptors. Stanozolol, an anabolic steroid, ends in -olol by chance.
- Every drug name stem
Its class
Beta blockers
Other beta blockers with a card:
Easily mixed up with alpha-1 blockers and non-dihydropyridine calcium channel blockers.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Metoprolol succinate extended-release tablets: label (DailyMed)
- Metoprolol (NCI Thesaurus)
- Metoprolol (NHS)
- Beta blockers (NHS)
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.
Blood pressure
Metoprolol is one of 27 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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