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Beta-Blocker Pregnancy: Use with caution — neonatal bradycardia, hypoglycaemia. Monitor neonate 24-48 hours after delivery.

Metoprolol (IV/Oral — Cardiology)

Brand names: Betaloc, Lopresor

Adult dose

Dose: IV: 2.5-5 mg slow IV injection over 5 minutes; repeat every 5 minutes to max 15 mg. Oral: 25-200 mg BD (immediate-release) or 47.5-190 mg OD (Betaloc ZOK succinate XL).
Route: Intravenous (acute) or Oral (maintenance)
Frequency: IV: repeat every 5 min as needed. Oral: BD (IR) or OD (XL).
Max: IV: 15 mg total. Oral: 400 mg/day.
Cardioselective beta-1 blocker. IV: rate control in AF/flutter, SVT, NSTEMI. Oral: HFrEF (metoprolol succinate XL — MERIT-HF trial). Use XL formulation for HFrEF — immediate-release tartrate not licensed for heart failure.

Paediatric dose

Dose: 0.1-0.2 mg/kg
Route: IV slow injection
Frequency: Repeat every 5 min if needed (max 3 doses)
Max: 5 mg per dose IV
Specialist paediatric cardiology only.

Dose adjustments

Renal

No dose adjustment required — primarily hepatically metabolised

Hepatic

Reduce dose in severe hepatic impairment

Paediatric weight-based calculator

Specialist paediatric cardiology only.

Clinical pearls

  • MERIT-HF trial (Lancet 1999): metoprolol succinate XL vs placebo in HFrEF — 34% reduction in all-cause mortality. Only the extended-release (succinate) formulation is licensed for HFrEF.
  • IV metoprolol for AF with RVR: 2.5-5 mg over 5 minutes, onset 2-5 min. Can repeat up to 3 doses. Preferred over digoxin for acute rate control in haemodynamically stable AF.
  • COMMIT trial (Chen et al. Lancet 2005): IV then oral metoprolol in acute STEMI — early IV metoprolol in haemodynamically unstable patients INCREASED cardiogenic shock risk. Avoid IV beta-blockers in acute HF.
  • CYP2D6 polymorphism: poor metabolisers achieve 5-fold higher plasma levels — increased side effects. CYP2D6 inhibitors (fluoxetine, paroxetine) significantly increase exposure.
  • Bisoprolol vs metoprolol: bisoprolol has longer half-life (10-12h vs 3-7h), more consistent once-daily dosing. Both guideline-recommended in HFrEF.

Contraindications

  • Cardiogenic shock
  • Uncontrolled heart failure
  • 2nd/3rd degree AV block (without pacemaker)
  • Severe bradycardia
  • Severe bronchospasm

Side effects

  • Bradycardia
  • Hypotension
  • Fatigue
  • Cold extremities
  • Bronchospasm (less than non-selective)
  • Sexual dysfunction
  • Masking of hypoglycaemia symptoms

Interactions

  • Non-dihydropyridine CCBs (verapamil, diltiazem) — life-threatening bradycardia/AV block; never give IV combination
  • Amiodarone — additive bradycardia
  • CYP2D6 inhibitors (fluoxetine, paroxetine) — increase metoprolol exposure 5-fold

Monitoring

  • Heart rate
  • Blood pressure
  • ECG (PR interval, AV conduction)
  • Signs of HF decompensation

Reference: BNFc; BNF 90; MERIT-HF Trial (Lancet 1999); COMMIT Trial (Chen et al. Lancet 2005); ESC HF Guidelines 2021; SPC Betaloc. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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