What is the maximum dose of carbimazole (antithyroid medication) for the treatment of hyperthyroidism?

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Last updated: February 27, 2025 • View editorial policy

From the Research

The maximum dose of carbimazole for hyperthyroidism is typically 40-60 mg per day, as supported by the most recent and highest quality study 1. For most adults with hyperthyroidism, treatment usually begins with 20-40 mg daily, divided into 2-3 doses, which can be increased to the maximum dose in severe cases. After achieving euthyroidism (usually within 4-8 weeks), the dose is gradually reduced to a maintenance dose of 5-15 mg daily. Carbimazole works by inhibiting thyroid peroxidase, the enzyme responsible for incorporating iodine into thyroglobulin, thereby reducing thyroid hormone production. Some key points to consider when treating hyperthyroidism with carbimazole include:

  • Patients should be monitored regularly with thyroid function tests to adjust dosing appropriately.
  • Common side effects include rash, pruritus, and arthralgia, while rare but serious side effects include agranulocytosis.
  • Patients should be advised to seek immediate medical attention if they develop signs of infection, particularly sore throat or fever.
  • Pregnant women typically require lower doses, and dose adjustments may be needed as pregnancy progresses due to changing thyroid physiology. It's also worth noting that the efficacy of carbimazole in a single daily dose has been compared to divided doses, with similar results 2. Additionally, the use of thyroxine in combination with carbimazole has been studied, but was found to have no significant effect on recurrence rates 3. Overall, the key to effective treatment with carbimazole is careful monitoring and dose adjustment to minimize side effects and achieve optimal thyroid hormone levels.

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