Metoprolol

Selective beta-adrenergic blockers

ATC code: C07AB02 (Metoprolol)

Mechanism of action

Selective beta-1 adrenergic receptor blocker. Reduces heart rate, myocardial contractility, and renin secretion. Available as two salts with fundamentally different pharmacokinetics. Tartrate is immediate-release, taken twice daily. Succinate is extended-release (XR/ZOK), taken once daily. In heart failure, only succinate has an evidence base (MERIT-HF trial). The formulations are not interchangeable.

Indications

Coronary artery disease

First line

Beta-blockers are first-line in stable angina. Metoprolol reduces heart rate and myocardial oxygen consumption, decreasing angina attack frequency. After MI, beta-blockers reduce the risk of recurrent MI and sudden death. Target resting heart rate is 55-60 bpm.

Heart failure

First line

Metoprolol succinate is one of three beta-blockers proven to reduce mortality in HFrEF. The MERIT-HF trial demonstrated a 34% reduction in all-cause mortality. Start at 12.5-25 mg daily, titrate every 2 weeks to target dose of 200 mg. Succinate must not be substituted with tartrate – they are not equivalent in HF. ESC 2021 includes metoprolol succinate among recommended beta-blockers for HF.

Only metoprolol succinate (extended-release form). Tartrate is not used in HF – no evidence base.

Hypertension

First line

Metoprolol is one of the beta-blockers prescribed for arterial hypertension. Tartrate 50-100 mg twice daily or succinate 50-200 mg once daily. Preferred with comorbid CAD, post-MI, or tachyarrhythmias. Less effective for stroke prevention compared to ACEi, ARBs, CCBs, and diuretics.

Supraventricular tachycardia

First line

Metoprolol is one of the first-choice agents for heart rate control and prevention of supraventricular tachycardia paroxysms. In acute SVT, metoprolol is given intravenously 5 mg over 2 minutes, repeatable up to 3 times at 5-minute intervals. Oral form is used for long-term prevention.

Practical notes

Special situations

Tartrate and succinate are not the same. Tartrate (plain Egilok) is taken twice daily, peak concentrations fluctuate, and missed doses are more critical. Succinate (Betaloc ZOK, Egilok Retard) is taken once daily, controlled release ensures stable blood levels. Only succinate is approved for HF. Do not crush or chew succinate tablets – this destroys the extended-release matrix.

Timing and administration

Take with or immediately after food (increases tartrate bioavailability). Do not stop abruptly – taper over 1-2 weeks. Sudden withdrawal causes rebound tachycardia and may provoke angina exacerbation or hypertensive crisis.

Safety

Contraindications

Second- or third-degree AV block without a pacemaker
Sick sinus syndrome without a pacemaker
Severe bradycardia (HR below 50 bpm before treatment)
Severe bronchial asthma
Decompensated heart failure with pulmonary edema or cardiogenic shock
Pheochromocytoma without prior alpha-blockade

Serious adverse effects

AV block
Bronchospasm (although selective, loses selectivity at high doses)
Masking of hypoglycemia symptoms in diabetic patients
Psoriasis exacerbation (rare)

Common adverse effects

Bradycardia
Hypotension
Fatigue, weakness
Dizziness
Cold extremities

PregnancyFDA C

FDA category C. Beta-blockers can cause fetal growth restriction, neonatal bradycardia, and hypoglycemia. If antihypertensive therapy is needed in pregnancy, labetalol or methyldopa are preferred.

Breastfeeding

Excreted in breast milk at concentrations exceeding plasma levels. Risk to the infant at standard doses is considered low, but monitor the neonate for signs of bradycardia.