Beta-Blockers: What They Do and Who Needs Them

Common Beta-Blockers and Their Uses

Side Effects

• Fatigue and tiredness: very common
• Cold hands and feet
• Slower heart rate (bradycardia): pulse <50 bpm needs medical review
• Worsening breathlessness (especially in asthma)
• Vivid dreams / nightmares (especially propranolol)
• Erectile dysfunction
• Masks hypoglycaemia symptoms in diabetics

Monitoring on Beta-Blockers

Never stop beta-blockers suddenly – why it matters

Stopping a beta-blocker abruptly can trigger rebound hypertension, unstable angina, or even a heart attack. This happens because the body upregulates (increases the number of) beta-adrenergic receptors during beta-blocker therapy. When the drug is suddenly withdrawn, these extra receptors respond to circulating adrenaline more powerfully than normal, dramatically increasing heart rate and blood pressure.

If a beta-blocker must be stopped – for example before surgery – it should be tapered gradually over 1–2 weeks whenever possible. If an urgent stop is unavoidable, close cardiovascular monitoring is needed in the days immediately after.

Which beta-blocker for which condition?

Beta-blockers differ in their selectivity for cardiac (beta-1) versus lung/vascular (beta-2) receptors, and in having additional properties:

• Bisoprolol / metoprolol / atenolol: Cardioselective (mainly beta-1); preferred in heart failure (bisoprolol), hypertension, and after heart attack. At higher doses, selectivity is lost.
• Carvedilol: Non-selective beta-blocker plus alpha-1 blocker; used in heart failure (with proven mortality benefit) and hypertension. Causes more vasodilation than cardioselective agents.
• Propranolol: Non-selective; used for tremor, anxiety, migraine prevention, thyrotoxicosis, and portal hypertension. Higher risk of bronchospasm.
• Labetalol / atenolol: Used in hypertension in pregnancy.
• Sotalol / atenolol (lower-dose): Rate control in atrial fibrillation.

Beta-blockers and asthma – a critical caution

Non-selective beta-blockers (propranolol, carvedilol, labetalol) are contraindicated in asthma because blocking beta-2 receptors in the bronchial smooth muscle causes bronchoconstriction. Even cardioselective agents (bisoprolol, metoprolol) carry a relative contraindication and should only be used in asthma when there is a compelling cardiac indication, at the lowest effective dose, with close monitoring for worsening breathlessness or wheeze.

Patients with COPD (not asthma) can usually tolerate cardioselective beta-blockers – and the mortality benefit in heart failure typically outweighs the small risk of worsening airflow obstruction.

References

Sources cited on this page. PubMed links open the original abstract.

1. Packer M, Coats AJ, Fowler MB, et al. Effect of carvedilol on survival in severe chronic heart failure. N Engl J Med. 2001;344(22):1651–1658. PMID 11386263 · doi:10.1056/NEJM200105313442201

How Beta-Blockers Work and Which Conditions They Treat

Beta-blockers (beta-adrenoceptor antagonists) block the binding of adrenaline (epinephrine) and noradrenaline to beta-adrenergic receptors, reducing heart rate, myocardial contractility, and – in higher doses – peripheral vascular resistance. Cardioselective beta-blockers (bisoprolol, metoprolol, atenolol) primarily block β1-receptors in the heart; non-selective agents (propranolol, carvedilol) block both β1 and β2 receptors, also affecting bronchial smooth muscle and peripheral vasodilation.

The evidence base for beta-blockers spans multiple conditions. In heart failure with reduced ejection fraction (HFrEF), bisoprolol, carvedilol, and sustained-release metoprolol reduce all-cause mortality by approximately 34% compared with placebo – one of the largest mortality benefits of any drug class in cardiovascular medicine.¹ In hypertension, they lower blood pressure through reduced cardiac output and, with chronic use, by resetting baroreceptor sensitivity. In angina, they reduce myocardial oxygen demand by limiting exercise-induced heart rate increases. They are first-line for rate control in atrial fibrillation and essential for secondary prevention post-myocardial infarction.

Blood Tests Required Before and During Beta-Blocker Treatment

Beta-blockers do not directly cause the laboratory abnormalities that some other cardiac drugs do, but monitoring is still structured around the conditions they treat. Before starting, baseline renal function (creatinine, eGFR) and electrolytes (potassium, sodium) are essential – hyperkalaemia can be worsened when beta-blockers are combined with ACE inhibitors, ARBs, or spironolactone, which is common in heart failure. Thyroid function (TSH) is checked because hyperthyroidism drives tachycardia and atrial fibrillation, and beta-blockers are used to control symptoms while definitive treatment is arranged; normalising thyroid function changes the dose required.

In people with diabetes, beta-blockers mask some of the sympathetic warning signs of hypoglycaemia (tremor, palpitations) while leaving sweating intact. Blood glucose monitoring becomes more important, and HbA1c testing every three months helps detect worsening glycaemic control. Liver function tests are relevant for propranolol, which is extensively hepatically metabolised; impaired liver function increases exposure and risk of bradycardia.²

Side Effects That Show Up in Blood Tests

Most beta-blocker side effects are haemodynamic (bradycardia, hypotension, fatigue, cold extremities) rather than metabolic, but some laboratory changes are clinically significant. Non-selective beta-blockers can raise triglycerides and lower HDL cholesterol – relevant when monitoring cardiovascular risk in patients already on a statin. Serum potassium requires periodic checking in patients on combination heart failure therapy, as the combination of beta-blocker, ACE inhibitor, and spironolactone carries hyperkalaemia risk. Creatinine and eGFR should be rechecked after any dose titration in patients with pre-existing chronic kidney disease, as reduced cardiac output from the drug can lower renal perfusion.