What is the preferred treatment between Propylthiouracil (PTU) and Methimazole for thyroid storm?

From the Guidelines

PTU is the preferred treatment over methimazole for thyroid storm due to its ability to block new thyroid hormone synthesis and inhibit the peripheral conversion of T4 to T3, providing faster control of thyroid hormone levels in critical situations. In thyroid storm, PTU is typically administered at a dose of 200-400 mg every 4-6 hours orally, via nasogastric tube, or rectally if necessary 1. This dual mechanism of action is particularly beneficial in the acute crisis of thyroid storm, as it helps to rapidly reduce thyroid hormone levels. Additionally, PTU should be given before administering iodine solutions (such as Lugol's solution or potassium iodide) to prevent the iodine from being used as substrate for additional thyroid hormone synthesis. While methimazole is generally safer for long-term use due to lower risk of severe hepatotoxicity, the acute benefits of PTU make it the preferred agent specifically for thyroid storm management 1. Some key points to consider when treating thyroid storm with PTU include:

• Administering PTU at a dose of 200-400 mg every 4-6 hours
• Using PTU to block new thyroid hormone synthesis and inhibit the peripheral conversion of T4 to T3
• Giving PTU before administering iodine solutions to prevent additional thyroid hormone synthesis
• Considering transition to methimazole for ongoing management once the patient is stabilized.

From the FDA Drug Label

Because of postmarketing reports of severe liver injury in pediatric patients treated with propylthiouracil, methimazole is the preferred choice when an antithyroid drug is required for a pediatric patient Given the potential maternal adverse effects of propylthiouracil (e.g., hepatotoxicity), it may be preferable to switch from propylthiouracil to methimazole for the second and third trimesters.

The preferred treatment between Propylthiouracil (PTU) and Methimazole for thyroid storm is not directly stated in the provided drug labels. However, based on the information provided, Methimazole is preferred over PTU in certain situations, such as in pediatric patients and in pregnant women during the second and third trimesters, due to the potential adverse effects of PTU.

• Key points:
  • Methimazole is preferred in pediatric patients due to reports of severe liver injury associated with PTU 2.
  • Methimazole may be preferred in pregnant women during the second and third trimesters due to the potential maternal adverse effects of PTU, such as hepatotoxicity 2. However, the provided drug labels do not directly compare PTU and Methimazole for the treatment of thyroid storm.

From the Research

Treatment Options for Thyroid Storm

The treatment of thyroid storm typically involves the use of antithyroid medications, such as propylthiouracil (PTU) and methimazole.

• PTU is often used as the initial treatment for thyroid storm due to its ability to inhibit the production of thyroid hormones and its rapid onset of action 3.
• Methimazole is also effective in treating thyroid storm, but it may be associated with a higher risk of adverse reactions, such as angioedema and dyspnea 4.

Comparison of PTU and Methimazole

Both PTU and methimazole are effective in treating hyperthyroidism, but they have different side effect profiles and mechanisms of action.

• PTU is associated with a higher risk of hepatotoxicity, particularly in pediatric patients 5.
• Methimazole is associated with a higher risk of teratogenicity, particularly when used during the first trimester of pregnancy 6, 5.
• Methimazole is generally considered the drug of choice for hyperthyroidism due to its widespread availability, longer half-life, and smaller number of severe side effects 7.

Rectal Administration of PTU

In cases where oral administration of PTU is not possible, rectal administration may be an effective alternative.

• Rectal administration of PTU has been shown to result in substantial absorption of the drug, with a bioavailability of at least 40% 3.
• This route of administration may be particularly useful in patients with thyroid storm who have upper gastrointestinal tract dysfunction.