Metoprolol

Metoprolol is a cardioselective beta-1 receptor blocker. It is used to treat high blood pressure, angina pectoris, and heart rhythm disorders, for prevention after a heart attack, and in heart failure.

Metoprolol is available in two salt forms: metoprolol succinate (extended-release form, e.g., Beloc Zok) for a steady effect over 24 hours and metoprolol tartrate (e.g., MetoHEXAL®, Metoprolol 50 - 1 A Pharma®) with a shorter duration of action.

Metoprolol is also used to treat functional heart complaints (racing heart when agitated) and for migraine prophylaxis.

Metoprolol selectively blocks the beta-1 receptors in the heart:

Mechanism of action:

• Cardioselective beta-1 blockade
• Lowers heart rate and blood pressure
• Reduces the heart's oxygen consumption
• Reduces renin release

Two formulations:

• Metoprolol tartrate: rapid onset of action, duration of action 8-12 hours, 1-2x daily
• Metoprolol succinate (extended-release/Zok): steady release, duration of action 24 hours, 1x daily

Additional effects:

• Antiarrhythmic effect (class II)
• Protection against ventricular fibrillation after a heart attack
• Migraine-preventive effect

Onset of action: Metoprolol tartrate: after 1-2 hours. Metoprolol succinate (extended-release): steady level of the active substance over 24 hours.

Metoprolol is suitable for:

• Adults with high blood pressure
• Angina pectoris (stable and unstable)
• Heart rhythm disorders (tachyarrhythmias)
• Chronic heart failure (stable, NYHA II-IV)
• After a heart attack (secondary prevention)
• Migraine prophylaxis
• Functional heart complaints

Especially recommended for:

• High blood pressure with tachycardia
• Coronary artery disease
• Heart failure as add-on therapy
• Atrial fibrillation for rate control

Not suitable:

• Severe bronchial asthma
• Second- or third-degree AV block
• Severe bradycardia (below 50/min)
• Decompensated heart failure
• Cardiogenic shock

High blood pressure (metoprolol succinate/extended-release):

• Starting dose: 47.5 mg (or 50 mg) once daily
• Usual dose: 95-190 mg once daily
• Maximum dose: 190 mg daily

High blood pressure (metoprolol tartrate):

• Starting dose: 50 mg twice daily
• Usual dose: 100-200 mg daily (divided)
• Maximum dose: 200 mg daily

Heart failure (metoprolol succinate only):

• Starting dose: 23.75 mg once daily
• NYHA class III: in the first week, half a 23.75 mg tablet (11.875 mg) once daily
• Slow increase every 2 weeks
• Target dose: 190 mg once daily

Available strengths:

• Tartrate: 50 mg, 100 mg, 200 mg
• Succinate (extended-release): 23.75 mg, 47.5 mg, 95 mg, 190 mg

Well-known products:

• Beloc Zok (metoprolol succinate)
• MetoHEXAL® (metoprolol tartrate)
• Metoprolol 50 - 1 A Pharma®

Taking metoprolol succinate (extended-release/Zok):

• Once daily, preferably in the morning
• Regardless of meals
• Swallow the tablet whole with water, without chewing
• Do not chew extended-release tablets
• Beloc Zok extended-release tablets can be split at the score line. Only the 23.75 mg tablet can be divided into equal doses. For the other strengths, the score line only serves to make swallowing easier

Taking metoprolol tartrate:

• Twice daily (morning and evening)
• With or after meals (improved absorption)
• Tablets can be split

Important notes:

• Never stop abruptly – taper off slowly!
• Regular pulse and blood pressure checks
• Inform anesthesiologists before surgery
• In patients with diabetes: monitor blood sugar closely

Metoprolol must not be taken in case of:

• Hypersensitivity to metoprolol or other beta blockers
• Second- or third-degree AV block
• Decompensated heart failure
• Severe bradycardia (below 50/min)
• Sick sinus syndrome (without a pacemaker)
• Cardiogenic shock
• Severe hypotension
• Severe bronchial asthma
• Untreated pheochromocytoma

Caution in:

• Mild asthma or COPD (low dose if needed)
• Diabetes mellitus
• Peripheral circulatory disorders
• Psoriasis
• Depression

Pregnancy: Only if strictly indicated. Can lead to fetal bradycardia and growth restriction. Close monitoring required.

Common (1-10%):

• Fatigue, dizziness
• Bradycardia (slow pulse)
• Cold extremities
• Gastrointestinal complaints
• Headache

Uncommon (0.1-1%):

• Weight gain
• Depressed mood
• Sleep disturbances, nightmares
• Erectile dysfunction
• Skin rash
• Shortness of breath on exertion

Rare:

• Bronchospasm
• Worsening of psoriasis
• Dry eyes (important for contact lens wearers)
• Elevated liver enzymes

Contraindicated with:

• Verapamil or diltiazem i.v.
• MAO inhibitors (except MAO-B inhibitors)

Caution with:

• Oral verapamil/diltiazem → increased bradycardia
• Antiarrhythmics → increased cardiodepressant effect
• Clonidine → rebound when both are stopped at the same time
• Digitalis preparations → increased bradycardia
• Adrenaline (epinephrine) → paradoxical rise in blood pressure possible
• CYP2D6 inhibitors (fluoxetine, paroxetine, quinidine) → increased metoprolol levels

Important: Metoprolol is broken down via CYP2D6. Medications that inhibit this enzyme can significantly increase the effect of metoprolol. About 7% of the population are poor CYP2D6 metabolizers and may need lower doses.