Propylthiouracil (PTU) Dosage and Usage for Hyperthyroidism
For adult patients with hyperthyroidism, the recommended initial dosage of propylthiouracil is 300 mg daily, divided into three equal doses given approximately every 8 hours, with a usual maintenance dose of 100-150 mg daily. 1
Initial Dosing
- For adults with standard hyperthyroidism: 300 mg daily (100 mg three times daily at 8-hour intervals) 1
- For adults with severe hyperthyroidism or very large goiters: Initial dose may be increased to 400 mg daily; occasionally patients may require 600-900 mg daily initially 1
- The goal of therapy is to maintain free T4 or Free T4 Index (FTI) in the high-normal range using the lowest possible thioamide dosage 2
Maintenance Dosing
- After initial control of hyperthyroidism is achieved, the usual maintenance dose is 100-150 mg daily 1
- Dose should be adjusted based on clinical response and thyroid function tests 2
- Monitoring free T4 or FTI every 2-4 weeks is recommended during initial treatment phase 2
Special Populations
Pregnant Women
- PTU is preferred over methimazole during the first trimester of pregnancy due to lower risk of birth defects 2, 3
- After first trimester, consider switching to methimazole due to PTU's higher risk of hepatotoxicity 2, 3
- Women treated with PTU can breastfeed safely 2
Pediatric Patients
- Generally not recommended in pediatric population except in rare instances when other therapies are not appropriate 1
- For children 6 years or older, when necessary: Start at 50 mg daily with careful upward titration based on clinical response and thyroid function tests 1
- Severe liver injury has been reported with doses as low as 50 mg/day, but most cases were associated with doses of 300 mg/day and higher 1
Elderly Patients
- Dose selection should be cautious, reflecting the greater frequency of decreased hepatic, renal, or cardiac function 1
- Start with lower doses and titrate carefully based on response 1
Monitoring and Adjustments
- Measure free T4 or FTI every 2-4 weeks during initial treatment phase 2
- Continue monitoring throughout treatment to maintain appropriate thyroid hormone levels 2
- For patients with Graves' disease, monitor heart rate and fetal growth if pregnant 2
Adjunctive Therapy
- Until thioamide therapy reduces thyroid hormone levels, a beta-blocker (e.g., propranolol) can be used to reduce symptoms 2
- In thyroid storm, additional treatments including high-dose corticosteroids may be necessary 2
Side Effects to Monitor
- Agranulocytosis: Usually presents with sore throat and fever; if these symptoms develop, obtain a complete blood count and discontinue PTU 2
- Hepatotoxicity: PTU has higher risk of liver injury compared to methimazole 3, 4
- Other potential side effects: hepatitis, vasculitis, and thrombocytopenia 2, 5
Comparative Efficacy
- For severe hyperthyroidism (FT4 ≥7 ng/dl), methimazole 30 mg/day normalizes FT4 more effectively than PTU 300 mg/day 6
- PTU is generally not recommended for initial use in non-pregnant adults due to higher risk of hepatotoxicity 3, 6
Important Precautions
- Monitor liver function tests periodically, especially in the first few months of therapy 4
- Instruct patients to report symptoms of liver injury (jaundice, dark urine, right upper quadrant pain) or infection (fever, sore throat) immediately 2, 7
- PTU should be discontinued immediately if agranulocytosis or significant hepatotoxicity develops 2, 7