From the Guidelines
Taking levothyroxine and methimazole together can be done under specific clinical circumstances, such as "block and replace" therapy for Graves' disease, but it requires close medical supervision and regular thyroid function testing. This approach involves using methimazole to block thyroid hormone production completely while simultaneously providing levothyroxine to maintain normal thyroid hormone levels 1. Levothyroxine increases thyroid hormone levels by providing synthetic thyroid hormone, while methimazole decreases thyroid hormone production.
Key Considerations
- The combination therapy should only be used under close medical supervision with regular thyroid function testing.
- If you are currently taking one of these medications and have been prescribed the other, contact your healthcare provider immediately for clarification.
- Never adjust your thyroid medication regimen without medical guidance, as improper thyroid hormone levels can cause serious health complications affecting your heart, bones, and overall metabolism.
Clinical Context
In the context of thyroid storm, which is an extreme hypermetabolic state associated with a high risk of maternal heart failure, methimazole is used as part of the treatment regimen 1. However, this does not directly relate to the use of levothyroxine and methimazole together in standard therapy.
Important Notes
- The study by 1 provides guidance on the treatment of thyroid storm, but it does not directly address the question of taking levothyroxine and methimazole together.
- The decision to use these medications together should be based on the specific clinical situation and should only be made under the guidance of a healthcare provider.
From the Research
Combination Therapy of Levothyroxine and Methimazole
- The combination of levothyroxine and methimazole has been studied for the treatment of hyperthyroidism in children and adults, with results indicating improved clinical efficacy and reduced adverse reaction rates 2, 3.
- A systematic review and meta-analysis of 15 studies involving 1,718 pediatric patients found that the combination of methimazole and levothyroxine had no significant difference in thyroid-stimulating hormone levels, but improved clinical treatment efficacy and reduced adverse reaction rates compared to methimazole alone 2.
- Another study of 102 patients with hyperthyroidism found that the combination of levothyroxine and methimazole resulted in a higher total effective rate and improved thyroid hormone levels, serum index levels, and thyroid volume compared to methimazole alone 3.
- A network meta-analysis of 21 randomized controlled trials found that methimazole combined with other medications, including levothyroxine, can regulate serum free triiodothyronine and free thyroxine levels and reduce relapse rates in patients with Graves hyperthyroidism 4.
Efficacy and Safety
- The combination of levothyroxine and methimazole has been shown to improve clinical efficacy and reduce adverse reaction rates in patients with hyperthyroidism 2, 3.
- The combination therapy has also been found to reduce thyroid volume and improve thyroid function and serum index levels 3.
- The safety profile of the combination therapy has been found to be higher than methimazole alone, with lower adverse reaction rates 2, 3.
Study Findings
- The studies found that the combination of levothyroxine and methimazole can be an effective and safe treatment option for hyperthyroidism in children and adults 2, 3, 4.
- The combination therapy has been found to improve clinical efficacy, reduce adverse reaction rates, and regulate serum thyroid hormone levels 2, 3, 4.