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Drug Reference

metoprolol

Beta-adrenergic blockers· Brands: Lopressor, Toprol-XL, Betaloc, Betaloc ZOK, SelokenIVPO

Mechanism of action
Metoprolol is a cardioselective beta-1 adrenergic receptor blocker. It competitively antagonises the effects of catecholamines at beta-1 receptors, reducing cardiac rate, contractility and conduction. It inhibits renin release from the kidney, decreasing angiotensin II and aldosterone. At higher doses, beta-2 selectivity is lost.
Pharmacokinetics
Metoprolol is well absorbed after oral administration, with extensive first-pass metabolism reducing systemic bioavailability to about 50%. It is metabolised by CYP2D6, with genetic polymorphism leading to variable plasma concentrations. Elimination half-life is approximately 3 to 7 hours, but therapeutic effects last longer. Metoprolol and its metabolites are primarily excreted in urine.
Indications & dosing

Hypertension

Immediate-release formulation; extended-release may be given once daily.

  • adult · PO: 50–100 mg BD · Immediate-release formulation; extended-release may be given once daily.

Angina pectoris

Titrate according to heart rate and symptoms.

  • adult · PO: 50–200 mg BD · Titrate according to heart rate and symptoms.

Chronic heart failure

Use metoprolol succinate extended-release; start low and titrate to target dose.

  • adult · PO: 12.5–25 mg OD · Use metoprolol succinate extended-release; start low and titrate to target dose.

Supraventricular tachyarrhythmias

Repeat after 2-5 minutes if needed; monitor ECG.

  • adult · IV: 2.5–5 mg Slow IV injection · Repeat after 2-5 minutes if needed; monitor ECG.

Acute myocardial infarction

Give as slow IV; follow with oral therapy.

  • adult · IV: 5 mg Every 5 minutes · Give as slow IV; follow with oral therapy.

Migraine prophylaxisoff-label

May be used off-label; effectiveness varies.

  • adult · PO: 50–100 mg BD · May be used off-label; effectiveness varies.
Contraindications & precautions
  • Severe bradycardia (heart rate <50 bpm) · Beta-blockade further reduces heart rate and can precipitate cardiac arrest.
  • Second or third degree atrioventricular block · Conduction delay is exacerbated, risking complete heart block.
  • Sick sinus syndrome · May cause severe bradycardia or sinus arrest.
  • Cardiogenic shock · Negative inotropic effect can worsen shock.
  • Decompensated heart failure · Beta-blockade can precipitate acute worsening; use only in stable, compensated heart failure.
  • Severe asthma or bronchospasm · Cardioselective, but selectivity is lost at higher doses; use with caution and consider alternative.
  • Prinzmetal's (variant) angina · Beta-blockade may exacerbate vasospasm; use with caution or avoid.
  • Do not withdraw abruptly; taper over 1-2 weeks to avoid rebound tachycardia or hypertension.
  • Use with caution in asthma or COPD; a beta-1 selective agent is preferred but bronchospasm can still occur.
  • Use with caution in diabetes mellitus, as beta-blockade may mask hypoglycaemia symptoms and delay recovery.
  • Use with caution in peripheral vascular disease, as vasoconstriction may worsen symptoms.
  • Use with caution in combination with verapamil or diltiazem, as additive bradycardia and heart block can occur.
  • In patients with heart failure, initiate at a low dose and titrate slowly under specialist supervision.
Adverse effects
  • Fatigue
  • Bradycardiaserious
  • Hypotension
  • Gastrointestinal upset (nausea, diarrhoea)
  • Bronchospasmserious
  • Worsening heart failureserious
  • Depression
  • Hypoglycaemia unawarenessserious
Interactions
  • diltiazemmajorCo-prescription should be approached with caution. Measure baseline heart rate, blood pressure, and ECG. Monitor these parameters regularly, especially after dose changes. Avoid the combination in patients with marked bradycardia, second or third degree AV block without a pacemaker, or significant heart failure. Consider alternative agents or lower doses with careful titration.
  • salbutamolmoderateIf co-prescription is necessary, use the lowest effective dose of metoprolol and consider a more cardioselective beta-blocker. Monitor respiratory function, including peak expiratory flow (PEF) or spirometry, and assess the patient's response to inhaled salbutamol. Advise patients to report any increase in shortness of breath or wheezing. In acute bronchospasm, use non-selective beta-agonists or anticholinergics may be considered. Where possible, avoid beta-blockers in patients with known asthma; if required, use cardioselective agents with caution. Regular assessment of clinical response to bronchodilators is essential.
  • verapamilmajorAvoid concomitant use. If unavoidable, monitor heart rate, blood pressure and ECG closely, and consider reducing the dose of metoprolol. Alternative calcium channel blockers such as amlodipine may be safer.
  • amiodaronemajorAlternative beta-blockers with minimal CYP2D6 metabolism (e.g., atenolol or nadolol) may be considered, but always assess clinically.
  • digoxinmoderateCo-prescription is acceptable but requires monitoring. Check heart rate and ECG before and during treatment, particularly when introducing or adjusting doses. Monitor for signs of bradycardia or heart block. Consider reducing doses of one or both agents if the heart rate is too low. Digoxin levels should be monitored if renal function changes.
Renal & hepatic adjustment
  • eGFR 0+: No dose adjustment required in renal impairment.
  • Hepatic impairment (moderate): Consider reducing the initial dose and titrate slowly.
  • Hepatic impairment (severe): Use with caution; consider dose reduction and monitor closely.
Monitoring, pregnancy & toxicity
  • Heart rate · Regularly during treatment
  • Blood pressure · Regularly during treatment
  • ECG · As clinically indicated
  • Signs and symptoms of heart failure · Regularly
  • Bronchospasm in patients with asthma/COPD · Regularly
  • Blood glucose in diabetic patients · Regularly
  • Pregnancy: Metoprolol is generally not recommended in pregnancy unless the benefits outweigh the risks. It may cause fetal bradycardia, growth restriction, and hypoglycaemia. Consider alternative agents if possible.
  • Toxicity: Bradycardia · Administer atropine; if unresponsive, consider glucagon or temporary pacing.
  • Toxicity: Hypotension · IV fluids, and if necessary, vasopressors such as norepinephrine.
  • Toxicity: Bronchospasm · Administer bronchodilators (e.g., salbutamol) and supportive care.
  • Toxicity: Heart failure · Supportive care, monitor fluid balance, consider inotropic support.
Antidotes & reversal
  • Glucagon · 1-5 mg IV then infusion; consider high-dose insulin-euglycaemia therapy and lipids if refractory.
Clinical notes
Used for hypertension, angina pectoris, heart failure, and myocardial infarction. In acute myocardial infarction, IV metoprolol may be given then transitioned to oral. Taper gradually to avoid rebound tachycardia and hypertension. Common adverse effects include bradycardia, fatigue, dizziness, and gastrointestinal upset. Contraindicated in severe bradycardia, heart block, decompensated heart failure, and severe asthma. Use with caution in diabetes and peripheral vascular disease.

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BNF; local formulary