Propranolol Dosing in Thyroid Storm
In thyroid storm, propranolol should be administered at 60-80 mg orally every 4-6 hours or 0.5-1 mg intravenously over 1 minute, repeated as required up to a total dose of 0.1 mg/kg. 1
Mechanism and Importance in Thyroid Storm
Propranolol is crucial in thyroid storm management for two key reasons:
- Blocks beta-adrenergic effects of excess thyroid hormone
- Uniquely inhibits peripheral conversion of T4 to active T3
Dosing Recommendations
Intravenous Administration
- Initial dose: 0.5-1 mg IV over 1 minute
- May repeat as required up to total dose of 0.1 mg/kg
- Use when rapid control is needed or oral route unavailable
Oral Administration
- 60-80 mg every 4-6 hours
- Total daily dose typically ranges from 160-320 mg/day
- Can be divided into 3-4 doses per day
Monitoring Parameters
- Heart rate: Target reduction to 90-100 beats per minute
- Blood pressure: Monitor for hypotension
- Temperature: Follow for normalization
- Respiratory status: Watch for bronchospasm
- Cardiac function: ECG monitoring recommended
Clinical Considerations and Cautions
Cardiovascular Collapse Risk: There have been reports of cardiovascular collapse following propranolol administration in thyroid storm with coexisting atrial fibrillation 2. Consider cardiac function before administration.
Contraindications:
- Asthma or chronic obstructive pulmonary disease
- Decompensated heart failure
- Heart block (second or third degree)
- Cardiogenic shock
Alternative Approaches:
Treatment Duration
Continue propranolol until thyroid hormone levels normalize and symptoms resolve, typically requiring several weeks of therapy in conjunction with antithyroid drugs, iodine solutions, and sometimes glucocorticoids 4.
Special Situations
Surgical Management: Propranolol alone (without iodine) can effectively prepare a thyrotoxic patient for thyroidectomy within 24 hours orally or less than an hour intravenously 5
Severe Cardiac Dysfunction: In patients with significant heart failure or cardiomyopathy, start with lower doses and titrate cautiously while monitoring cardiac function
Remember that propranolol is just one component of thyroid storm management, which should include antithyroid drugs, iodine solutions, and supportive care.