What is Propylthiouracil?

Mary McMahon

Propylthiouracil or PTU is an antithyroid medication used in the management of an overactive thyroid gland to lower the levels of thyroid hormone in the body. This medication may be used alone as a solo form of therapy to bring a patient's hormone levels down and keep them at a safe level. It can also be used in patients preparing for surgical treatment of hyperthyroidism. One of the most common reasons to prescribe this medication is for the treatment of Grave's disease, a frequent cause of hyperthyroidism.

Breaking out in hives can be a side effect of propylthiouracil.
Breaking out in hives can be a side effect of propylthiouracil.

This medication was approved for use in the 1940s. It comes in the form of tablets. Initial doses are usually high to force thyroid hormone levels to drop, and over time, the patient is tapered to a lower dosage safe for long term usage. The patient will be monitored by an endocrinologist as the dosage is adjusted to find the point where thyroid hormone production stays stable and balanced. Follow-up appointments can be used to confirm the treatment is still working well for the patient.

Propylthiouracil functions by blocking the production of thyroid hormone in the body. It inhibits the actions of enzymes involved in hormone synthesis. The medication starts working in the body very quickly and the life of a dose can be eight hours or more. The most common side effects associated with propylthiouracil use are related to the skin. Patients can develop rashes, itching, hives, and other forms of skin irritation as reactions to the medication.

Less commonly, the medication can cause issues like nausea, joint pain, swelling, vomiting, and headache. Patients can also develop bleeding disorders and a decrease in white blood cells. Studies show that propylthiouracil is dangerous in pregnancy, although there may be cases when concerns about the health of the mother outweigh this risk, and propylthiouracil is safer than some other antithyroid medications, making it the best choice when a pregnant woman's hyperthyroidism absolutely must be controlled pharmacologically.

In 2009, the Food and Drug Administration in the United States noted an increased incidence of serious liver problems among patients taking propylthiouracil, and in 2010, it added a warning to the prescription packaging. People with a history of liver disease may not be able to take this medication and periodic liver function testing for patients on the drug may be recommended to monitor the liver's condition, allowing doctors to take quick action if a patient begins to experience an adverse reaction to the medication.

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