The propylthiouracil dilemma

To bring to the attention of healthcare professionals the additional information on propylthiouracil (PTU)-related hepatotoxicity, based on a reanalysis of medical files reported to the Food and Drug Administration (1982-2008) for acute liver failure in PTU-treated hyperthyroid patients, and propose recommendations for the clinical use of PTU. Thirteen files of PTU-related severe liver adverse effects were analyzed for the pediatric population, seventeen for nonpregnant adults and two for pregnant women.

The recent findings showed that the daily PTU dose administered was high in the children, with a mean of 300 mg/day for an average 10-year-old individual. With regard to treatment duration, PTU administration lasted for at least 4 months in 75% of pediatric cases. Similarly, in a majority of adult cases (64%), PTU-induced liver injury occurred after a relatively long treatment period (4 months to >1 year).

PTU should not be used in children, in whom methimazole (MMI) represents the logical alternative. In adults, PTU should be restricted to those rare patients with Graves' disease for whom no better alternative can be offered and in patients with thyroid storm. For the special circumstance of pregnancy, PTU is the preferred choice during early gestation; switching back to MMI during later gestational stages remains a matter of clinical judgment. It is unknown whether liver function tests monitoring is worthwhile to prevent life-threatening, PTU-related hepatotoxicity.