Beta-Blockers USMLE Questions: 15 High-Yield Pharmacology MCQs with Answers

Carvedilol blocks β1, β2 and α1 receptors. β-blockade lowers heart rate, contractility and renin release. α1-blockade dilates blood vessels and lowers peripheral resistance. This combination makes it useful in hypertension and heart failure (it lowers mortality in HFrEF).

Why the other options are wrong:

• A describes amlodipine or other calcium channel blockers.
• B describes clonidine and methyldopa.
• D describes metoprolol, atenolol and bisoprolol.

Atenolol is cardioselective (β1). Labetalol blocks α1, β1 and β2, so it lowers blood pressure by both slowing the heart and dilating vessels. Labetalol is a first-line drug for hypertension in pregnancy and is given IV in hypertensive emergencies.

Why the other options are wrong: no commonly used β-blocker is β2-selective, and atenolol has no α-blocking effect. Only carvedilol and labetalol add α1-blockade.

Propranolol blocks both β1 and β2 receptors. It is used for hypertension, angina, arrhythmias, essential tremor, migraine prevention, thyroid storm and performance anxiety. Because it blocks β2, it can cause bronchospasm.

Why the other options are wrong: atenolol, bisoprolol and metoprolol are all β1-selective (the “A to M” group).

Metoprolol blocks β1 receptors in the heart. This lowers heart rate, contractility and AV-node conduction (a class II antiarrhythmic effect). It also lowers renin release from the kidney, which helps control blood pressure.

Why the other options are wrong:

• A is the opposite effect; dobutamine is a β1 agonist.
• C describes calcium channel blockers.
• D describes ACE inhibitors.

Metoprolol is cardioselective. It blocks β1 receptors in the heart much more than β2 receptors in the airways, so it is less likely to cause bronchospasm. Selectivity is relative, so it should still be used with care in asthma.

Why the other options are wrong: labetalol, propranolol and timolol all block β2 receptors and can trigger bronchospasm. Even timolol eye drops can be absorbed enough to cause an asthma attack.

β2 receptors relax bronchial smooth muscle. Propranolol blocks β2, so the airways constrict. This is why non-selective β-blockers are avoided in asthma.

Why the other options are wrong: propranolol has no α1-blocking effect and does not stimulate β1 (it blocks it). Muscarinic activation causes bronchospasm, but propranolol does not act on muscarinic receptors.

Tremor is amplified by β2 receptors in skeletal muscle. Propranolol blocks them and reduces the tremor. Propranolol and primidone are the first-line drugs for essential tremor.

Why the other options are wrong:

• A describes benzodiazepines (and partly primidone).
• C is wrong because β1 blockade alone does not reduce tremor.
• D would make tremor worse; β2 agonists such as albuterol cause tremor.

β-blockers hide the adrenergic warning signs of hypoglycemia: tachycardia, palpitations and tremor. Non-selective β-blockers can also slow recovery from hypoglycemia, because they block β2-mediated glycogenolysis. Cardioselective drugs are preferred in diabetics.

Why the other options are wrong: sweating is driven by sympathetic cholinergic fibers, so it is not blocked. Hunger and confusion come from low glucose in the brain, not from β receptors.

β-blockers lower heart rate, contractility and blood pressure, so the heart needs less oxygen. A slower heart rate also lengthens diastole, which gives the coronary arteries more time to fill. β-blockers are first-line for stable angina but are avoided in vasospastic (Prinzmetal) angina.

Why the other options are wrong: β-blockers block the receptor; they do not reduce epinephrine production. Raising venous pressure or peripheral resistance would increase the heart’s workload.

A slower heart rate gives more time for filling, so EDV increases. Weaker contraction means the ventricle takes longer to empty, so ejection time increases. Both changes raise oxygen demand a little. This is why β-blockers are often combined with nitrates in angina: nitrates lower EDV and offset this effect.

Why the other options are wrong: both values go up, not down, with β-blockade.

β-blockers slow conduction through the AV node. In a patient who already has partial (first- or second-degree) AV block, propranolol can push it into complete heart block, which can be life-threatening.

Why the other options are wrong: angina, SVT and tremor are all conditions that propranolol treats.

Nadolol has a half-life of about 20 to 24 hours and is cleared by the kidneys, so it can be given once a day. It is non-selective and is used with propranolol to prevent variceal bleeding in cirrhosis.

Why the other options are wrong: metoprolol (short-acting form) and propranolol have short half-lives and are often given two or more times a day. Sotalol lasts about 12 hours. Esmolol is the shortest-acting β-blocker (minutes).

Class II antiarrhythmics are β-blockers, such as metoprolol, esmolol, propranolol and carvedilol. They slow AV-node conduction and are used for rate control in atrial fibrillation and to prevent arrhythmias after a heart attack.

Why the other options are wrong:

• Amiodarone is class III (potassium channel blocker).
• Procainamide is class IA (sodium channel blocker).
• Verapamil is class IV (calcium channel blocker).

Sotalol is a class III antiarrhythmic (it blocks potassium channels and prolongs repolarization) and also a non-selective β-blocker. Its main danger is QT prolongation and torsades de pointes, so the QT interval is monitored when it is started.

Why the other options are wrong: sotalol has no α1, calcium channel or sodium channel blocking effect.

Glucagon acts on its own receptor, which bypasses the blocked β receptor and activates adenylate cyclase. This raises cAMP and improves heart rate and contractility. It is the antidote of choice for severe β-blocker overdose that does not respond to fluids and atropine.

Why the other options are wrong:

• Calcium is the first antidote for calcium channel blocker overdose (it can be added in β-blocker overdose, but glucagon comes first).
• Naloxone reverses opioids.
• Sodium bicarbonate treats tricyclic antidepressant overdose.
• Flumazenil reverses benzodiazepines.

FREE USMLE PDFs

Get 80 free practice questions

Four free sampler PDFs by Dr. Ray Makar: Step 1 (Pathology & Pharmacology) and Step 2 CK (Medicine, Surgery & Pediatrics), in both Review style and USMLE style, with answers and explanations. Also useful for NEET-PG, INI-CET and FMGE.