Anti-Thyroid Drug Associated with Serious Liver Injury


The use of the anti-thyroid drug propylthiouracil has been associated with the risk of serious liver injury. The U.S. Food and Drug Administration (FDA) issued a warning to health care professionals earlier this week regarding the drug which is used in the treatment of Graves' disease.

Amy Egan, M.D., deputy director for safety, Division of Metabolism and Endocrinology Products, in the FDA’s Center for Drug Evaluation and Research is quoted as stating "After analyzing adverse event reports, the FDA has identified an increased risk of liver injury with propylthiouracil when compared to an alternative treatment for Graves' disease, methimazole. Health care professionals should carefully consider which drug to initiate in a patient recently diagnosed with Graves' disease. If propylthiouracil therapy is chosen, the patient should be closely monitored for symptoms and signs of liver injury, especially during the first six months after initiating therapy."

Propylthiouracil, approved for marketing in 1947, has been associated with a total of 32 cases of serious liver injury since the establishment of the FDA's Adverse Event Reporting System in 1969 through October 2008. There have been 22 adult cases. Of these, 12 resulted in deaths and five required liver transplants. There have been 10 pediatric cases. Of these, one resulted in death and six resulted in liver transplants.


Graves' disease is an autoimmune disorder that leads to overactivity of the thyroid gland (hyperthyroidism). Graves' disease is rarely life-threatening. Graves' disease may develop at any age and in either men or women, but is more common in women and usually begins after age 20.

Symptoms of Graves' disease may include anxiety, difficulty sleeping, fatigue, a rapid or irregular heartbeat, increased perspiration, sensitivity to heat, unintended weight loss, brittle hair, enlargement of your thyroid gland (goiter), light menstrual periods, and frequent bowel movements. Graves’ disease may also involve the eye, causing the eyeball to bulge out past its protective orbit (exophthalmos).

Propylthiouracil is considered second-line drug therapy, except in certain patients who are allergic to, or intolerant of, methimazole. Because a rare birth defect has been reported with methimazole and not with propylthiouracil, propylthiouracil may be more appropriate for patients with Graves' disease who are in the first trimester of pregnancy.

FDA News Release
Mayo Clinic (Graves Disease)