Propylthiouracil Linked With Risk for Serious Liver Damage, Death

Neil Osterweil

June 03, 2009

June 3, 2009 — The US Food and Drug Administration (FDA) issued a safety alert today about the risk for serious liver damage, including liver failure, or death with propylthiouracil (PTU) compared with methimazole. Both agents are approved for the treatment of hyperthyroidism associated with Graves' disease.

“Health care professionals should carefully consider which drug to initiate in a patient recently diagnosed with Graves’ disease," Amy Egan, MD, deputy director for safety, Division of Metabolism and Endocrinology Products, in the FDA’s Center for Drug Evaluation and Research, said in a news release. "If PTU 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.”

Physicians should promptly discontinue PTU therapy when liver damage is suspected; such patients should be evaluated and supportive care provided if needed.

The agency notes that 22 adult cases and 10 pediatric cases of serious liver injury linked to PTU use have been reported to its Adverse Event Reporting System. Twelve of the adult patients died and 5 required liver transplantation. In the pediatric cases, 1 child died and 6 required liver transplantation. In contrast, only 5 cases of serious liver injury associated with methimazole use have been reported. These cases, all in adults, resulted in 3 deaths.

"PTU is considered second-line drug therapy except in patients who are allergic to or intolerant of methimazole," according to an alert from MedWatch, the FDA's safety information and adverse event reporting program. "Rare cases of embryopathy, including aplasia cutis, have been reported with use of [methimazole] during pregnancy, while no such cases have been reported with PTU use. Thus, PTU may be more appropriate for patients with Graves' disease who are in their first trimester of pregnancy."

"PTU should not be used in pediatric patients unless the patient is allergic to or intolerant of methimazole, and there are no other treatment options available," the FDA points out.

Any adverse events associated with PTU should be communicated to the FDA's MedWatch reporting program by telephone at 1-800-FDA-1088, by fax at 1-800-FDA-0178, online at, or by mail to 5600 Fishers Lane, Rockville, Maryland 20852-9787.


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