Propylthiouracil Gets Boxed Warning For Liver Injury Risk

A boxed warning has been added to the label of <"">propylthiouracil, a drug used to treat hyperthyroidism (overactive thyroid) associated with Grave’s disease. The new boxed warning says reports of severe liver injury and acute liver failure, some of which have been fatal, have been received from adult and pediatric patients using propylthiouracil.

The FDA says it has identified 34 cases of severe liver injury associated with propylthiouracil. Twenty-three cases were in adult patients and 11 were in pediatric patients. Of the 23 adult cases, 13 deaths and five liver transplants were reported. Among the 11 pediatric cases, two cases resulted in death and seven patients required a liver transplant; one patient died while on the transplant list.

In comparison, the FDA identified only five cases of severe liver injury reported with methimazole. All five cases were in adult patients and three resulted in death. Based on these findings, and a review of the medical literature, the agency concluded that use of propylthiouracil is associated with a higher risk for clinically serious or fatal liver injury compared to methimazole in both adult and pediatric patients.

The new boxed warning states that for patients being started on treatment for hyperthyroidism it may be appropriate to reserve use of propylthiouracil for those who cannot tolerate other treatments such as methimazole, radioactive iodine or surgery. In addition, due to the occurrence of birth defects that have been observed with the use of methimazole during the first trimester of pregnancy, propylthiouracil may be the treatment of choice during and just before the first trimester of pregnancy.

The FDA is advising that patients be made aware that severe liver injury has occurred in patients taking propylthiouracil. Patients should contact their healthcare professional if they experience fever, loss of appetite, nausea, vomiting, tiredness, itchiness, dark colored urine, or yellowing of the skin or eyes while taking propylthiouracil.

Finally, the FDA is also advising healthcare providers that propylthiouracil is not recommended for use in pediatric patients, except in rare instances in which other alternative treatments are not appropriate.

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