How will taking metoprolol (beta blocker) extended release twice daily affect heart rate and blood pressure?

Metoprolol Extended Release Effects on Heart Rate and Blood Pressure

Taking metoprolol extended release twice daily is inappropriate dosing that deviates from evidence-based practice—metoprolol succinate (extended release) should be administered once daily, not twice daily, as this is the specific formulation and dosing regimen proven to reduce mortality in clinical trials. 1, 2

Critical Dosing Error to Avoid

• The American College of Cardiology and American Heart Association specifically warn that dosing metoprolol succinate twice daily is inappropriate and deviates from the evidence-based regimen used in mortality-reducing trials. 2
• Metoprolol succinate extended release is designed for once-daily administration with a dosing range of 50-400 mg once daily. 1, 2
• The confusion often arises because metoprolol tartrate (immediate release) requires twice-daily dosing at 25-100 mg BID, but this is a different formulation that was not proven to reduce mortality in heart failure trials. 1, 2

Hemodynamic Effects of Proper Metoprolol ER Dosing (Once Daily)

Heart Rate Reduction

• Metoprolol reduces heart rate through beta-1 receptor blockade, slowing the sinus rate and decreasing AV nodal conduction. 3
• Clinical studies demonstrate reduction in heart rate both at rest and during exercise through competitive antagonism of catecholamines at cardiac adrenergic receptor sites. 3
• The goal for rate control is typically 50-60 beats per minute at rest, though this may vary by indication. 1

Blood Pressure Reduction

• Metoprolol reduces systolic blood pressure during exercise and causes reduction in cardiac output at rest and upon exercise. 3
• The antihypertensive effect occurs through multiple mechanisms: decreased cardiac output from beta-1 blockade, reduced sympathetic outflow centrally, and suppression of renin activity. 3
• In acute myocardial infarction studies, metoprolol administration caused reductions in heart rate, systolic blood pressure, and cardiac output, while diastolic blood pressure remained unchanged. 3

Pharmacokinetic Considerations Supporting Once-Daily Dosing

• Metoprolol succinate extended release provides sustained beta-blockade over 24 hours with once-daily administration, unlike immediate-release formulations. 4
• The extended-release formulation produces lower peak plasma levels and less peak-to-trough variation compared to immediate-release metoprolol, resulting in more uniform beta-blockade throughout the day. 4
• Maximum beta-blockade is achieved approximately 20 minutes after intravenous administration, with a linear relationship between plasma levels and reduction of exercise heart rate. 3

Evidence-Based Dosing Regimens

For Heart Failure

• Start with 12.5-25 mg once daily and titrate gradually by doubling the dose every 1-2 weeks if tolerated. 2
• Target dose is 200 mg once daily (maximum recommended dose), with mean achieved dose in clinical trials of 159 mg daily. 2
• This regimen reduced mortality by 34% in the MERIT-HF trial. 2

For Hypertension

• Usual dose range is 50-400 mg once daily. 1, 2
• Typical starting dose is 25-50 mg once daily with gradual titration to target. 2

For Tachycardia

• The American College of Cardiology recommends 50-400 mg daily (extended release) for rate control. 1
• Beta blockers achieve heart rate control endpoints in 70% of patients. 1

Monitoring Parameters

• Monitor for hypotension (systolic BP <85 mmHg), symptomatic bradycardia, and signs of heart failure exacerbation during titration. 1, 2
• Assess heart rate control both at rest and during physical activity. 1
• Monitor for worsening renal function during uptitration in heart failure patients. 2

Common Pitfall

Never abruptly discontinue metoprolol, as this may precipitate angina, myocardial infarction, or arrhythmias. 2