Beta blockers
Blocking beta receptors, so the heart beats slower and less forcefully.
Also called beta-adrenergic blockers, β-blockers and beta-adrenoceptor antagonists.
Class card
- Drugs
- Propranolol, Atenolol, Metoprolol, Bisoprolol, Carvedilol and Labetalol
- Used for
- High blood pressure, though no longer usually first-line
- Angina
- Slowing the heart in atrial fibrillation
- Heart failure (bisoprolol, carvedilol, metoprolol)
- Known for
- Slow heart rate (bradycardia)
- Narrowed airways (bronchospasm), worst if non-selective
- Hidden warning signs of low blood sugar
- Name stems
- -olol, -alol, -dilol
7 cards: the class, and each drug in it.
Mechanism of action
How do beta blockers work?
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.
The drugs
Beta blockers with a card
- PropranololBeing non-selective, it is the beta blocker also used outside the heart: for migraine, essential tremor, anxiety symptoms and thyroid overactivity.
- AtenololWater-soluble and cleared by the kidneys, unlike propranolol and metoprolol, which the liver metabolizes.
- MetoprololIts level depends on CYP2D6, so genes and interacting drugs make it vary more than most beta blockers' levels do.
- BisoprololThe US label covers only high blood pressure; the NHS also lists angina and heart failure.
- CarvedilolIts α1 blockade adds vasodilation to beta blockade, so dizziness and fainting on standing are typical in the first weeks.
- LabetalolIts combined α1 and β blockade makes it a choice for high blood pressure in pregnancy and, given IV, for severe hypertension.
Uses
What are beta blockers used for?
- High blood pressure, though no longer usually first-line
- Angina
- Slowing the heart in atrial fibrillation
- Heart failure (bisoprolol, carvedilol, metoprolol)
- After a heart attack
- Migraine prevention
Side effects
Side effects of beta blockers
- Slow heart rate (bradycardia)Known for
- Narrowed airways (bronchospasm), worst if non-selectiveKnown forSerious
- Hidden warning signs of low blood sugarKnown forSerious
- Cold hands and feet
- Tiredness
- Heart blockSerious
- Worsening heart failure, especially when startingSerious
- Angina or a heart attack if stopped suddenlySerious
- Vivid dreams, nightmares and poor sleep
- Erectile dysfunction
What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.
Watch for
Cautions
- Asthma: non-selective ones are contraindicated, and even cardioselective ones need great care.
- Never stop them suddenly: taper over 1 to 2 weeks or more, or angina and heart attacks can follow.
- Contraindicated in marked bradycardia, heart block beyond first degree, cardiogenic shock and decompensated heart failure.
- With verapamil or diltiazem, slowing of the heart rate and AV conduction adds up.
Remember them
A way to remember them
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
Name stems
-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.
-alol means beta blocker (labetalol type)
USAN reads it as a combined alpha and beta blocker, which labetalol is. WHO defines it by chemical structure, as a sub-stem of -olol, and also lists sotalol.
-dilol means vasodilating beta blocker
WHO files -dilol under -dil (vasodilators). Carvedilol blocks beta receptors and also alpha-1 receptors, which widens blood vessels.
- Every drug name stem
Don't mix them up
Classes easily confused with these
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Beta-Adrenergic Antagonist (NCI Thesaurus)
- Beta blockers (NHS)
- Propranolol hydrochloride tablets: label (DailyMed)
- Atenolol tablets: label (DailyMed)
- Metoprolol succinate extended-release tablets: label (DailyMed)
- Guideline for the pharmacological treatment of hypertension in adults (WHO)
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
Practice beta blockers with the other classes in this group: what each drug is, how it works, what it treats and what it's known for.
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