What is the dose of metoprolol (beta-blocker) in abdominal aortic aneurysm (AAA) and hypertension (HTN)?

Metoprolol Dosing for Abdominal Aortic Aneurysm and Hypertension

For patients with abdominal aortic aneurysm (AAA) and hypertension, metoprolol should be initiated at 50 mg twice daily and titrated to achieve a target systolic blood pressure between 100-120 mmHg while maintaining adequate perfusion.

Rationale for Beta-Blocker Therapy in AAA

Beta-blockers are the cornerstone of medical management for patients with AAA and hypertension for several important reasons:

• They reduce the force of left ventricular ejection (dP/dt), which decreases stress on the arterial wall 1
• They slow aneurysm expansion rates, particularly in large aneurysms (≥5 cm) 2
• They help achieve target blood pressure goals recommended by current guidelines 1

Specific Dosing Recommendations

Oral Metoprolol Regimen:

• Initial dose: Metoprolol 50 mg twice daily 1
• Titration: Adjust dose to achieve target systolic BP of 100-120 mmHg 1
• Maximum daily dose: Up to 200 mg daily in divided doses

Intravenous Metoprolol (for perioperative or acute settings):

• Bolus dosing: 5 mg IV bolus, can be repeated at 5-minute intervals
• Maximum IV dose: 15 mg total 1

Blood Pressure Targets

• Target systolic BP: 100-120 mmHg 1
• Target heart rate: 60 bpm or less 1
• For patients with chronic hypertension and AAA, aim for BP <130/80 mmHg 1

Monitoring Parameters

• Regular blood pressure monitoring
• Heart rate (maintain ≥50 bpm)
• Signs of heart failure or bronchospasm
• Aneurysm size via imaging (typically every 6-12 months depending on size)

Clinical Evidence

The evidence supporting beta-blocker use in AAA comes from several studies:

• Propranolol has been shown to reduce aneurysm expansion in hypertensive animal models 3
• Metoprolol significantly reduced the expansion rate of large AAAs (≥5 cm) from 0.68 cm/yr to 0.36 cm/yr 2
• Beta-blockers are associated with decreased incidence of perioperative myocardial infarction in patients undergoing vascular surgery 1

Important Considerations and Cautions

• Contraindications: Avoid in patients with severe bradycardia, high-degree AV block, cardiogenic shock, or severe bronchospasm
• Perioperative use: Continue beta-blockers perioperatively for patients undergoing AAA repair 1
• Combination therapy: If beta-blockers alone don't control hypertension, consider adding ARBs or ACE inhibitors 1, 4
• Avoid abrupt discontinuation: May precipitate rebound hypertension or tachycardia

Alternative Beta-Blockers

If metoprolol is not tolerated or contraindicated:

• Esmolol: Ultra-short acting, can be used at 50-300 μg/kg/min IV for acute management 1
• Labetalol: Combined alpha and beta-blocker, can be used at 200-800 mg/day in divided doses 1
• Bisoprolol: Has shown benefit in perioperative settings at doses of 2.5-10 mg daily 1

Beta-blockers remain the first-line therapy for patients with AAA and hypertension due to their ability to reduce aortic wall stress and potentially slow aneurysm growth, while effectively managing blood pressure.