What is the typical dosage and usage of Metoprolol (beta-blocker) for conditions like hypertension, angina, and heart failure?

Metoprolol Dosing and Usage

Metoprolol is a beta-1 selective blocker with proven mortality benefit in heart failure and established efficacy in hypertension and angina, requiring careful dose titration and formulation selection based on the specific indication. 1

Heart Failure with Reduced Ejection Fraction (HFrEF)

For heart failure, metoprolol succinate (CR/XL) provides a 34% reduction in all-cause mortality and should be the preferred formulation. 1

Dosing Protocol

• Start at 12.5-25 mg once daily of metoprolol succinate (CR/XL) in stable patients already on ACE inhibitors and diuretics 1, 2
• Titrate gradually every 2 weeks by doubling the dose until reaching the target of 200 mg once daily 1, 2
• At study conclusion, 64% of patients achieved the full 200 mg daily target dose 1
• The mean effective dose in clinical trials was 159 mg daily 2

Mortality Benefits

• 34% reduction in all-cause mortality 1
• 38% reduction in cardiovascular mortality 1
• 41% reduction in sudden death 1
• 49% reduction in death from progressive heart failure 1
• 35% reduction in heart failure hospitalizations 1
• Number needed to treat: 27 patients for 1 year to prevent 1 death 1

Critical Contraindications

• Signs of decompensated heart failure or low output state 1, 2
• Systolic blood pressure <120 mmHg 2
• Heart rate <60 bpm or >110 bpm 2
• Second or third-degree AV block without pacemaker 1, 2
• Active asthma or reactive airways disease 1, 2

Stable Angina Pectoris

For angina, metoprolol CR 200 mg once daily is the target dose for full anti-anginal effects. 1

Dosing Protocol

• Target dose: metoprolol CR 200 mg once daily or atenolol 100 mg daily or bisoprolol 10 mg once daily 1
• Alternative: conventional metoprolol 100-400 mg daily in divided doses 3
• Metoprolol CR demonstrated superior exercise tolerance improvement compared to nifedipine SR in the IMAGE study 1

Mechanism and Efficacy

• Reduces oxygen demand by decreasing heart rate, contractility, and blood pressure 1
• Prolongs diastolic perfusion time to ischemic areas 1
• Increases exercise tolerance and decreases angina frequency 1, 3
• Caution: May worsen symptoms in vasospastic angina 1

Hypertension

For hypertension, initiate metoprolol tartrate at 25-50 mg twice daily or metoprolol succinate 50-200 mg once daily. 2, 3

Dosing Protocol

• Metoprolol tartrate: 25-50 mg twice daily initially, maximum 200 mg daily 2
• Metoprolol succinate (extended-release): 50-200 mg once daily, maximum 400 mg daily 2
• Effective dosage range in clinical trials: 100-450 mg daily 3
• Titrate every 1-2 weeks if blood pressure control not achieved 2

Monitoring

• Target resting heart rate: 50-60 beats per minute unless limiting side effects occur 2
• Target blood pressure reduction: at least 20/10 mmHg, ideally to <140/90 mmHg 2

Acute Myocardial Infarction

For acute MI, administer three 5 mg IV boluses at 2-minute intervals, followed by oral therapy 15 minutes after the last IV dose. 3

Early IV Protocol

• 5 mg IV over 1-2 minutes, repeated every 2 minutes for total of 15 mg 3
• Monitor blood pressure, heart rate, and ECG continuously during IV administration 3
• Exclude patients with: hypotension, bradycardia, peripheral shock signs, or more than minimal basal rales 3

Transition to Oral Therapy

• If full IV dose tolerated: 50 mg orally every 6 hours starting 15 minutes after last IV dose, continue for 48 hours 3
• If partial tolerance: 25 mg orally every 6 hours 3
• Maintenance: 100 mg twice daily after initial 48 hours 3

Mortality Benefit

• 36% reduction in 3-month mortality when treatment initiated within 8 hours of symptom onset 3
• Significant reductions in ventricular fibrillation and chest pain 3

Critical Warning

• High-risk patients for cardiogenic shock: age >70 years, systolic BP <120 mmHg, heart rate <60 or >110 bpm, prolonged time from symptom onset 2
• The COMMIT trial showed increased cardiogenic shock risk with early IV metoprolol in high-risk acute MI patients 2

Atrial Fibrillation Rate Control

For atrial fibrillation, use metoprolol tartrate 25-100 mg twice daily or metoprolol succinate 50-400 mg once daily. 2

Acute IV Dosing

• 5 mg IV over 1-2 minutes, repeated every 5 minutes to maximum 15 mg total 2
• Transition to oral therapy 15 minutes after last IV dose 2
• Oral: 25-50 mg every 6 hours for 48 hours, then twice daily maintenance 2

Target Heart Rate

• Resting heart rate: 50-60 beats per minute unless limiting side effects 2

Special Populations

Hepatic Impairment

• Initiate at low doses with cautious gradual titration 3
• Elimination half-life prolonged up to 7.2 hours depending on severity 3
• Blood levels increase substantially due to decreased first-pass metabolism 3

Renal Impairment

• No dose adjustment required 3
• Systemic availability and half-life do not differ clinically from normal subjects 3

Geriatric Patients

• Use low initial starting dose due to decreased hepatic and renal function 3
• Slightly higher plasma concentrations but not clinically significant 3

Poor CYP2D6 Metabolizers

• Several-fold higher plasma concentrations 3
• Half-life may extend to 7-9 hours (vs. 3-4 hours in extensive metabolizers) 3
• Decreased cardioselectivity at higher concentrations 3

Common Pitfalls and Adverse Effects

Side Effects to Monitor

• Cold extremities and symptomatic bradycardia (related to cardiac inhibition) 1
• Fatigue (occurs in only 0.4% of patients) 1
• Hypotension, bronchospasm, and bradycardia 2
• Increased respiratory symptoms in asthma/COPD (less common with beta-1 selective agents) 1

Critical Errors to Avoid

• Never administer IV metoprolol in decompensated heart failure 2
• Do not use in pre-excitation with atrial fibrillation 2
• Avoid abrupt cessation to prevent rebound hypertension or worsening angina 2
• Do not combine with heart rate-lowering calcium channel blockers without careful monitoring for conduction disturbances 1