Propranolol Starting Dose for Hyperthyroidism
For adults with hyperthyroidism, initiate propranolol at 40–80 mg orally every 6–8 hours (total daily dose 160–320 mg), or in critically ill patients with thyroid storm, administer 0.5–1 mg IV slowly over 10 minutes. 1
Dosing Strategy by Clinical Severity
Mild to Moderate Thyrotoxicosis
- Start with 40 mg orally every 6 hours (160 mg/day total) 1
- This conventional dose is frequently insufficient to achieve adequate beta-blockade, particularly in younger patients or those with more severe disease 2, 3
- Titrate objectively to achieve >25% reduction in exercise heart rate at the end of a dosage interval, which correlates with adequate beta-adrenergic blockade 2, 3
- Many patients require doses exceeding 160 mg/day—younger and severely thyrotoxic patients in particular need higher doses 2
Severe Thyrotoxicosis or Thyroid Storm
- Initiate at the upper end of the range: 80 mg orally every 6–8 hours (240–320 mg/day) 1
- For patients unable to take oral medications or in critical condition, give 0.5–1 mg IV slowly over 10 minutes, repeated as clinically indicated 1
- Severely thyrotoxic patients commonly require supplemental propranolol postoperatively even after initial control 3
Critical Pharmacokinetic Consideration
Thyrotoxicosis increases propranolol clearance by approximately 40%, necessitating higher doses than in euthyroid patients. 4 The oral clearance of propranolol is significantly elevated in the thyrotoxic state (4.2 L/min vs 2.7 L/min when euthyroid), and the free fraction of drug is higher (14.2% vs 11.4%), meaning standard doses produce lower plasma concentrations 4. This explains why conventional 160 mg/day dosing is often inadequate 2, 3.
Mandatory Pre-Treatment Assessment
Before administering the first dose, screen for absolute contraindications 1, 5:
- Second- or third-degree AV block (without pacemaker) 1
- Active asthma or severe obstructive airway disease—propranolol can precipitate life-threatening bronchospasm 1, 5
- Decompensated heart failure or cardiogenic shock 1, 5
- Sinus node dysfunction (without pacemaker) 5
- Severe hypotension 5
Measure baseline heart rate and blood pressure before initiating therapy 1.
Titration and Monitoring
- Objective endpoint: Achieve >25% reduction in sitting or exercise pulse rate at the end of the dosing interval 2, 3
- Monitor heart rate and blood pressure closely, especially in the first 24 hours after initiation 1
- Watch for signs of excessive beta-blockade: bradycardia <60 bpm, systolic BP <90 mmHg, worsening dyspnea, dizziness, or marked fatigue 1, 5
- Plasma propranolol concentration correlates significantly with both beta-adrenergic blockade and weight stabilization, though not with subjective symptom improvement 2
Common Pitfall: Underdosing
The most frequent error is using a fixed 160 mg/day dose without objective titration. 2, 3 In one surgical series, conventional 160 mg/day was insufficient in many patients, and failure to titrate to adequate beta-blockade led to complicated postoperative courses in severely thyrotoxic patients 3. Always titrate to the physiologic endpoint of >25% heart rate reduction rather than relying on a standard dose 2, 3.
Adjunctive Therapy Requirement
Propranolol alone is NOT adequate primary therapy for hyperthyroidism—it provides symptomatic control but does not correct the underlying thyrotoxicosis 6. Always combine with 1:
- Antithyroid drugs (methimazole or propylthiouracil)
- Corticosteroids in thyroid storm
- Iodine administration (given at least 1 hour after antithyroid drugs) 1
- Treatment of the precipitating cause 1
Propranolol monotherapy results in incomplete symptomatic control, fails to correct weight loss, and does not fully normalize myocardial contractility 6.
Discontinuation Warning
Never abruptly discontinue propranolol after chronic use—taper gradually over several weeks to prevent rebound tachycardia and worsening thyrotoxicosis 1.