When should metoprolol (beta-blocker) be given to patients?

Indications for Metoprolol Administration

Metoprolol should be administered for hypertension, angina pectoris, myocardial infarction, supraventricular tachycardia, and heart failure, with specific dosing protocols and contraindications for each condition. 1, 2

Cardiovascular Indications

Hypertension

• Initial dosing of metoprolol tartrate is 25-50 mg twice daily, with metoprolol succinate (extended-release) at 50-200 mg once daily 2
• Maximum dose is 200 mg daily for metoprolol tartrate and 400 mg daily for metoprolol succinate 2
• Target blood pressure reduction should be at least 20/10 mmHg, ideally to 140/90 mmHg 2

Angina Pectoris

• Effective dosage ranges from 100-400 mg daily, administered orally two or four times daily 3
• Reduces number of angina attacks and increases exercise tolerance 3

Myocardial Infarction (Early Treatment)

• Initiate treatment as soon as possible after patient's arrival in hospital and hemodynamic stabilization 3
• Begin with three bolus injections of 5 mg IV metoprolol at approximately 2-minute intervals 3
• For patients who tolerate the full IV dose (15 mg), initiate oral metoprolol tartrate 50 mg every 6 hours, 15 minutes after the last IV dose and continue for 48 hours 3
• Maintenance dosage is 100 mg orally twice daily thereafter 3
• It is reasonable to administer IV beta blockers at presentation to STEMI patients with no contraindications who are hypertensive or have ongoing ischemia 1

Supraventricular Tachycardia

• For stable, narrow-complex tachycardias if rhythm remains uncontrolled or unconverted by adenosine or vagal maneuvers 1
• IV administration: 5 mg over 1-2 minutes, repeated as required every 5 minutes to maximum dose of 15 mg 1, 2

Heart Failure

• Metoprolol CR/XL is effective in patients with chronic heart failure due to left ventricular systolic dysfunction 4
• Initiate at a low dosage (12.5-25 mg once daily) and gradually increase at 2-week intervals 4
• Target dosage is 200 mg once daily or maximum tolerated dosage 4

Contraindications and Precautions

Absolute Contraindications

• Signs of heart failure or cardiogenic shock 1
• Low output state 1
• PR interval greater than 0.24 seconds 1
• Second or third-degree heart block without a functioning pacemaker 1
• Active asthma or reactive airways disease 1

Risk Factors for Cardiogenic Shock

• Age greater than 70 years 1
• Systolic blood pressure less than 120 mm Hg 1
• Sinus tachycardia greater than 110 bpm or heart rate less than 60 bpm 1
• Increased time since symptom onset 1

Special Populations

• For patients with hepatic impairment, initiate at low doses with cautious gradual titration 3
• No dose adjustment required for renal impairment 3
• For elderly patients (>65 years), use a low initial starting dose 3

Monitoring During Treatment

• Monitor blood pressure, heart rate, and ECG during IV administration 3
• Target resting heart rate is 50-60 beats per minute unless limiting side effects occur 1
• Monitor for signs of worsening heart failure or bronchospasm, particularly during initiation 2

Clinical Pearls and Pitfalls

• Early IV beta-blockers in STEMI showed neutral effect on combined endpoint of death, recurrent MI, or cardiac arrest in the COMMIT trial 1
• While IV beta-blockers reduced recurrent MI and ventricular fibrillation, they increased risk of cardiogenic shock, especially in the first 24 hours 1
• For patients with acute heart failure, beta-blockers should be used cautiously when more than basal pulmonary rales are present 1
• In patients with AMI who stabilize after developing acute heart failure, beta-blockers should be initiated early 1
• For chronic heart failure patients, initiate beta-blockers only after stabilization (usually after 4 days) 1
• Avoid abrupt cessation of therapy to prevent rebound hypertension or worsening of angina 2