Drug interactions
Methimazole + Potassium iodide
Severity: Moderate
Methimazole and Potassium iodide: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Both agents reduce thyroid hormone output, and iodide also inhibits hormone release. Together they can produce additive suppression, with a risk of hypothyroidism and goiter if used over a prolonged period. The combination is used deliberately for short periods, for example before thyroid surgery or in thyroid storm.
What this interaction means in plain words
Methimazole and Potassium iodide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Methimazole belongs to Endocrine; Potassium iodide belongs to Endocrine.
Why it happens
Additive pharmacodynamic suppression of thyroid hormone synthesis and release.
What to do
Limit the combination to short, defined courses. Monitor thyroid function and watch for signs of hypothyroidism or goiter if therapy is prolonged.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Methimazole
- Carbamazepine + Methimazole Major
- Clozapine + Methimazole Major
- Methimazole + Propylthiouracil Major
- Methimazole + Sodium iodide i-131 Major
- Iodinated glycerol + Methimazole Moderate
- Iodine + Methimazole Moderate
Other interactions of Potassium iodide
- Amiloride + Potassium iodide Moderate
- Amlodipine-benazepril + Potassium iodide Moderate
- Amlodipine-hydrochlorothiazide-valsartan + Potassium iodide Moderate
- Amlodipine-olmesartan-hydrochlorothiazide + Potassium iodide Moderate
- Amlodipine-olmesartan + Potassium iodide Moderate
- Amlodipine-perindopril + Potassium iodide Moderate
Frequently asked questions
Can I take Methimazole with Potassium iodide?
MediHelp rates the interaction as moderate. Methimazole and Potassium iodide can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Both agents reduce thyroid hormone output, and iodide also inhibits hormone release. Together they can produce additive suppression, with a risk of hypothyroidism and goiter if used over a prolonged period. The combination is used deliberately for short periods, for example before thyroid surgery or in thyroid storm.
How serious is the interaction between Methimazole and Potassium iodide?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Limit the combination to short, defined courses. Monitor thyroid function and watch for signs of hypothyroidism or goiter if therapy is prolonged.
What other medicines interact with Methimazole?
MediHelp also lists interactions of Methimazole with, for example, Carbamazepine, Clozapine, Propylthiouracil. The full list is on the Methimazole page.
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