What is the recommended approach for converting an adult patient with hypertension or cardiovascular disease from nadolol (beta-blocker) to propranolol (beta-blocker)?

Converting from Nadolol to Propranolol

Use a 1:1 dose ratio when converting from nadolol to propranolol, but divide the total daily propranolol dose into 2-4 administrations per day since propranolol requires multiple daily dosing while nadolol is given once daily. 1

Conversion Protocol

Step 1: Determine Equivalent Daily Dose

• Convert nadolol to propranolol using a 1:1 ratio (e.g., nadolol 80 mg once daily = propranolol 80 mg total daily dose) 1
• Research demonstrates that in 60% of patients, the effective total daily dose of propranolol and nadolol was identical, with an overall dose ratio of 1.17:1 (propranolol to nadolol) across all patients 1
• However, individual dose titration is recommended because 40% of patients showed dosage variability when switching between these agents 1

Step 2: Divide Propranolol into Multiple Daily Doses

• Administer propranolol in 2-4 divided doses per day rather than once daily, as propranolol has a shorter duration of action compared to nadolol's inherently long duration 2, 1
• For immediate-release propranolol, the American College of Cardiology recommends 30-60 mg in divided doses with a maximum of 40-160 mg in divided or single dose with long-acting formulations 3
• Example conversion: Nadolol 80 mg once daily → Propranolol 40 mg twice daily (or 20 mg four times daily for immediate-release)

Step 3: Verify No Contraindications Before Switching

Check for absolute contraindications that apply to both agents 3, 4:

• AV block greater than first degree or SA node dysfunction without a pacemaker
• Decompensated systolic heart failure or cardiogenic shock
• Active asthma or reactive airway disease
• Hypotension (systolic BP <100 mmHg with symptoms)

Step 4: Initiate Propranolol with Monitoring

• Start propranolol the day after the last nadolol dose to avoid overlap, given nadolol's longer half-life 2
• Monitor blood pressure and heart rate at each visit during the transition 3
• Watch for bradycardia, hypotension, bronchospasm, and worsening heart failure as potential adverse effects common to both agents 3, 4

Step 5: Titrate Based on Clinical Response

• Adjust propranolol dose every 1-2 weeks based on blood pressure and heart rate response 3
• Target resting heart rate of 50-60 beats per minute unless limiting side effects occur 5
• Maximum propranolol dose is 160 mg daily in divided doses for most indications, though higher doses may be used in specific circumstances 3, 4

Critical Differences Between Nadolol and Propranolol

Pharmacokinetic Distinctions

• Nadolol is excreted entirely unchanged and not metabolized, while propranolol undergoes extensive hepatic metabolism 2
• Nadolol has a longer duration of action (12.2-hour half-life) allowing once-daily dosing, whereas propranolol requires multiple daily doses 2, 6
• Propranolol dosage may need reduction in patients with liver disease due to decreased drug clearance, while nadolol may be preferred in hepatic dysfunction 7

Shared Properties

• Both are nonselective beta-blockers without cardioselectivity 3, 2
• Both demonstrate comparable efficacy in controlling hypertension and angina 8, 1
• Both have similar adverse effect profiles including hypotension, bradycardia, and bronchospasm 3, 4

Common Pitfalls to Avoid

• Never abruptly discontinue nadolol before starting propranolol, as this can precipitate rebound hypertension, exacerbation of angina, myocardial infarction, and ventricular arrhythmias 7, 4
• Do not assume a simple 1:1 conversion will work for all patients—40% showed dosage variability requiring individual titration 1
• Avoid using propranolol in pre-excited atrial fibrillation, as it may precipitate very rapid ventricular rates 4
• Do not combine propranolol with other AV nodal blocking agents (calcium channel blockers, digoxin) without careful monitoring, as profound bradycardia can develop 3
• In diabetic patients, recognize that propranolol masks hypoglycemia symptoms and requires extreme caution 4

Special Populations

Patients with Liver Disease

• Propranolol requires dose reduction in hepatic impairment due to decreased clearance 7
• Avoid doses >160 mg/day total in decompensated cirrhosis, as higher doses are associated with worse survival outcomes 4

Patients with Alcohol Consumption

• Start at lower propranolol doses (10-20 mg three times daily) in patients with known heavy alcohol consumption 7
• Consider three-times-daily dosing to maintain more consistent blood levels 7