What are the recommended dosages of Propylthiouracil (PTU) and beta blockers (propranolol) in the management of thyroid storm?

PTU and Beta Blocker Dosing in Thyroid Storm

Propylthiouracil (PTU) Dosing

For thyroid storm, administer PTU 600-900 mg orally as a loading dose, followed by 200-250 mg every 4-6 hours (total daily dose 600-900 mg initially). 1, 2

• The FDA-approved dosing for severe hyperthyroidism allows initial doses of 600-900 mg daily, divided into doses given approximately every 8 hours 2
• PTU is preferred over methimazole in thyroid storm because it blocks both thyroid hormone synthesis AND peripheral conversion of T4 to T3 1
• After the loading dose, continue PTU at 200-250 mg every 4-6 hours until clinical improvement occurs 1
• Administer saturated potassium iodide solution (SSKI) or sodium iodide 1-2 hours AFTER starting PTU, never before, as iodine given first can worsen thyrotoxicosis 1

Beta Blocker Dosing

Propranolol (First-Line for Stable Patients)

Administer propranolol 60-80 mg orally every 4-6 hours for hemodynamically stable patients with thyroid storm. 1

• Propranolol is the most widely studied beta-blocker for thyroid storm and has the dual advantage of controlling adrenergic symptoms while also blocking peripheral T4 to T3 conversion 1
• The typical oral dosing is 60-80 mg every 4-6 hours, though exact dosing varies based on individual patient response 1
• Continue high doses until heart rate stabilizes below 90 bpm and blood pressure remains stable for 48-72 hours 3

Esmolol (For Hemodynamically Unstable Patients)

For patients with hemodynamic instability or requiring careful titration, use esmolol with a loading dose of 500 mcg/kg (0.5 mg/kg) IV over 1 minute, followed by maintenance infusion starting at 50 mcg/kg/min. 1

• Esmolol is preferred in unstable patients due to its ultra-short half-life, allowing rapid titration and immediate reversal if cardiovascular collapse occurs 1
• After the initial loading bolus, give a second loading dose of 0.5 mg/kg over 1 minute if needed, then increase maintenance infusion to 100 mcg/kg/min 1
• Titrate incrementally up to a maximum of 300 mcg/kg/min as needed to control heart rate 1
• Continuous cardiac monitoring is mandatory, checking blood pressure and heart rate every 5-15 minutes during titration 1
• Monitor for hypotension, bradycardia, heart failure, and hyperkalemia (particularly in patients with renal impairment) 1

Critical Treatment Sequence

1. Start PTU immediately at 600-900 mg loading dose 1, 2
2. Wait 1-2 hours, then give iodine solution (SSKI or sodium iodide) 1
3. Administer beta-blocker (propranolol 60-80 mg PO every 4-6 hours OR esmolol IV if unstable) 1
4. Give corticosteroids (dexamethasone or hydrocortisone) to reduce T4 to T3 conversion and treat possible relative adrenal insufficiency 1
5. Provide supportive care including oxygen, antipyretics for fever, and treatment of precipitating factors 1

Special Considerations and Monitoring

• Recent comparative effectiveness research found no significant mortality difference between PTU and methimazole in thyroid storm (8.5% vs 6.3%, adjusted risk difference 0.6%, P=0.64), though PTU remains guideline-preferred due to its additional mechanism of blocking peripheral conversion 4
• Never use beta-blockers as monotherapy—they must be combined with thionamides, as beta-blockers alone do not address the underlying thyrotoxicosis 1
• In pregnancy, the same treatment protocol applies, but monitor fetal status closely and avoid delivery during active thyroid storm unless absolutely necessary 1
• Monitor for agranulocytosis with thionamide use and cardiac complications such as heart failure throughout treatment 1
• Atrial fibrillation complicating thyroid storm requires oral anticoagulation (INR 2-3) to prevent thromboembolism, as antiarrhythmic drugs and cardioversion are generally unsuccessful while thyrotoxicosis persists 3

Medication Tapering After Stabilization

• Taper beta-blockers first after heart rate remains <90 bpm and blood pressure has been stable for 48-72 hours, reducing dose by 25% every 2-3 days 3
• Maintain full thionamide doses until free T4 and T3 approach the upper limit of normal 3
• Discontinue iodine solutions abruptly within 3-5 days rather than tapering 3
• Monitor thyroid function tests every 2-3 weeks during the tapering phase 3