PTU Dose in Thyroid Storm
Administer propylthiouracil (PTU) at 200 mg orally every 4-6 hours (800-1200 mg/day total) as the preferred first-line thionamide for thyroid storm, given its dual mechanism of blocking both thyroid hormone synthesis and peripheral T4 to T3 conversion. 1
Initial Thionamide Selection and Dosing
PTU is the preferred thionamide over methimazole in thyroid storm because it uniquely inhibits peripheral conversion of T4 to T3 in addition to blocking thyroid hormone synthesis. 1
The typical PTU dosing regimen is 200 mg orally every 4-6 hours, which translates to 800-1200 mg daily in divided doses. 2
If PTU is unavailable or contraindicated due to hepatotoxicity concerns, methimazole can be substituted, though it lacks the peripheral conversion blocking effect. 1
Critical Timing Considerations
Administer PTU immediately upon diagnosis of thyroid storm, before any iodine preparations. 1
Wait 1-2 hours after starting PTU before giving iodine solutions (saturated potassium iodide or sodium iodide) to prevent worsening thyrotoxicosis from iodine-induced hormone release. 1
This sequencing is crucial—administering iodine before thionamides can paradoxically worsen the thyrotoxic state. 1
Maintenance and Tapering Strategy
Maintain full PTU doses until free T4 and T3 levels approach the upper limit of normal, which typically takes several weeks. 3, 4
Monitor thyroid function tests every 2-3 weeks during treatment to guide dose adjustments. 3
Once thyroid hormones normalize, reduce PTU by 30-50% with continued monitoring. 4
Important Safety Considerations
Monitor closely for agranulocytosis and hepatotoxicity, which are potentially fatal complications of PTU therapy. 1, 2
Acute hepatitis can develop rapidly with PTU, manifesting as markedly elevated transaminases (ALT >800 U/L) even within 2-3 weeks of therapy. 2
If hepatotoxicity develops, immediately discontinue PTU and manage with high-dose corticosteroids (60 mg prednisolone daily) while continuing beta-blockade. 2
In cases where patients cannot tolerate PTU or methimazole, therapeutic plasma exchange is a safe alternative that can rapidly normalize thyroid hormones. 5
Adjunctive Therapy Requirements
Always combine PTU with beta-blockers (propranolol 60-80 mg every 4-6 hours orally, or esmolol IV if hemodynamically unstable) to control adrenergic symptoms. 1
Add corticosteroids (dexamethasone or prednisolone 30-60 mg daily) to further block peripheral T4 to T3 conversion and treat possible relative adrenal insufficiency. 1, 2
Provide aggressive supportive care including oxygen, antipyretics for fever control, and treatment of precipitating factors. 1