Typical Doses of Medications for Managing Hyperthyroidism
For adults with hyperthyroidism, methimazole should be initiated at 15 mg daily for mild disease, 30-40 mg daily for moderate disease, and 60 mg daily for severe disease, divided into three doses at 8-hour intervals. 1
Methimazole (MMI) Dosing
Adult Dosing
- Initial dosing:
- Mild hyperthyroidism: 15 mg daily
- Moderate hyperthyroidism: 30-40 mg daily
- Severe hyperthyroidism: 60 mg daily
- Typically divided into 3 doses at 8-hour intervals 1
- Maintenance dosing: 5-15 mg daily 1
- Single daily dosing option: 15 mg once daily has been shown effective for mild to moderate disease, with 30 mg once daily more suitable for severe cases 2, 3
Pediatric Dosing
- Initial dose: 0.4 mg/kg/day divided into 3 doses at 8-hour intervals
- Maintenance dose: Approximately half of the initial dose 1
Propylthiouracil (PTU) Dosing
Adult Dosing
- Initial dose: 300 mg daily
- Severe hyperthyroidism or large goiters: 400 mg daily initially
- Exceptional cases: 600-900 mg daily initially
- Maintenance dose: 100-150 mg daily
- Typically divided into 3 equal doses at 8-hour intervals 4
Pediatric Dosing
- Generally not recommended except in rare instances
- For children ≥6 years: 50 mg daily with careful upward titration based on clinical response and thyroid function tests
- Caution: Severe liver injury has been reported with doses as low as 50 mg/day, but most cases occurred with doses ≥300 mg/day 4
Beta-Blockers (e.g., Propranolol)
While specific dosing information for beta-blockers in hyperthyroidism was not provided in the evidence, beta-blockers are mentioned as medications that can impair T4 to T3 conversion 5. Based on general medical knowledge:
- Propranolol:
- Typical starting dose: 10-40 mg 3-4 times daily
- Dose can be adjusted based on heart rate control
- Target heart rate typically <90 beats per minute
Radioactive Iodine
Specific dosing information for radioactive iodine was not provided in the evidence.
Clinical Considerations and Comparative Efficacy
MMI vs. PTU effectiveness: MMI is more effective than PTU at equivalent doses. A single daily dose of 15 mg MMI was shown to be more effective than 150 mg PTU in inducing euthyroidism in Graves' disease 6
MMI dosing for severe cases: In patients with severe hyperthyroidism (FT4 ≥7 ng/dl), MMI 30 mg/day normalized free T4 more effectively than PTU 300 mg/day or MMI 15 mg/day 2
Side effect profile: PTU has higher rates of adverse effects, especially mild hepatotoxicity, compared to MMI. MMI 15 mg/day has significantly lower adverse effects than MMI 30 mg/day 2
Duration of therapy: Long-term methimazole therapy (60-120 months) has been shown to result in higher remission rates (85%) compared to conventional 18-24 month courses (47%) 7
Important Caveats
- PTU is generally not recommended as first-line therapy due to higher risk of hepatotoxicity, except in specific situations (first trimester of pregnancy, thyroid storm)
- Elderly patients may require lower doses due to increased risk of adverse effects 4
- Monitor thyroid function tests (TSH, free T4) regularly to adjust dosing
- Be aware that beta-blockers can impair T4 to T3 conversion 5
- Always check for medication interactions and adjust doses accordingly