Methimazole: uses, dosing, side effects & brands
Methimazole is a thyroid hormone synthesis inhibitor sold in the U.S. under 2 brand and generic names, for goiter and thyroid crisis. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Thyroid Hormone Synthesis Inhibitor
- Treats
- Goiter and Thyroid Crisis
- Available as
- Tablet
- Sold as
- 2 products — Methimazole and Tapazole
- Prescription?
- Prescription only
- Generic available?
- Yes
- What the pharmacy pays
- about $2 for a 30-count supply — not your price
How methimazole is dosed
From the FDA label for Methimazole (application ANDA040547). Other methimazole products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Methimazole tablets are administered orally. The total daily dosage is usually given in 3 divided doses at approximately 8-hour intervals. Adult - The initial daily dosage is 15 mg for mild hyperthyroidism, 30 to 40 mg for moderately severe hyperthyroidism, and 60 mg for severe hyperthyroidism, divided into 3 doses at 8-hour intervals. The maintenance dosage is 5 to 15 mg daily. Pediatric - Initially, the daily dosage is 0.4 mg/kg of body weight divided into 3 doses and given at 8-hour intervals. The maintenance dosage is approximately ½ of the initial dose.
Methimazole side effects
Major adverse reactions (which occur with much less frequency than the minor adverse reactions) include inhibition of myelopoiesis (agranulocytosis, granulocytopenia, thrombocytopenia, and aplastic anemia), drug fever, a lupus-like syndrome, insulin autoimmune syndrome (which can result in hypoglycemic coma), hepatitis (jaundice may persist for several weeks after discontinuation of the drug), periarteritis, and hypoprothrombinemia. Nephritis occurs very rarely. There have been postmarketing case reports of acute pancreatitis. There are reports of a vasculitis, often associated with the presence of anti-neutrophilic cytoplasmic antibodies (ANCA), resulting in severe complications [see WARNINGS ] . Minor adverse reactions include skin rash, urticaria, nausea, vomiting, epigastric distress, arthralgia, paresthesia, loss of taste, abnormal loss of hair, myalgia, headache, pruritus, drowsiness, neuritis, edema, vertigo, skin pigmentation, jaundice, sialadenopathy, and lymphadenopathy. To report SUSPECTED ADVERSE REACTIONS, contact AiPing Pharmaceutical, Inc. at 1-844-374-0016 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
Who shouldn’t take methimazole
Methimazole tablets are contraindicated in the presence of hypersensitivity to the drug or any of the other product components.
Methimazole drug interactions
Anticoagulants (oral): Due to potential inhibition of vitamin K activity by methimazole, the activity of oral anticoagulants (e.g., warfarin) may be increased; additional monitoring of PT/INR should be considered, especially before surgical procedures. ß-adrenergic blocking agents: Hyperthyroidism may cause an increased clearance of beta blockers with a high extraction ratio. A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid. Digitalis glycosides: Serum digitalis levels may be increased when hyperthyroid patients on a stable digitalis glycoside regimen become euthyroid; a reduced dosage of digitalis glycosides may be needed. Theophylline: Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.
Every methimazole product we track (2)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | Not yet rated | Prescription | Tablet | Generic | $2 | View → | |
| 2 | Not yet rated | Prescription | Tablet | Generic | $2 | View → |
What methimazole pills look like
Imprint codes, colour and shape from the FDA’s labelling data. Match the imprint on your pill — or search any imprint.
How long methimazole keeps
No methimazole label we read sets a separate limit for after opening, but they do specify how it must be stored — and the stability behind any date assumes those conditions.
Does methimazole expire? The in-use limits and storage rules from its labelsMethimazole and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for methimazole: levels in milk, effects in breastfed infants, and the drugs it would consider insteadMaternal methimazole therapy does not affect thyroid function or intellectual development in breastfed infants with doses up to 20 mg daily. Taking methimazole right after nursing and waiting for 3 to 4 hours before nursing again should minimize the infant dosage. No cases of thyroid function alteration have been reported among infants exposed to methimazole via breastmilk. Some experts now recommend that methimazole in doses up to 20 mg daily should be considered the antithyroid drug of choice in nursing mothers.
National Institute of Child Health and Human Development, record revised June 15, 2026. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about methimazole
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 8,032 reports naming methimazole, and the FDA flagged 71% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- fatigue453 reports
- hyperthyroidism416 reports
- nausea401 reports
- diarrhoea351 reports
- headache348 reports
- dizziness316 reports
- dyspnoea287 reports
- agranulocytosis260 reports
Read these as a signal, not a rate. A report does not mean methimazole caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
Related calculators
Frequently asked questions
What is methimazole?
Methimazole is a thyroid hormone synthesis inhibitor used to treat Goiter, Thyroid Crisis.
What kind of drug is methimazole?
The FDA classifies methimazole as a thyroid hormone synthesis inhibitor. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take methimazole with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run methimazole against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is methimazole sold under?
We track 2 methimazole-containing products in the U.S.: Methimazole and Tapazole. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does methimazole come in?
Across the brands we track, methimazole is currently marketed as tablet, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic methimazole?
Yes. Our catalog lists 1 generic methimazole product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Methimazole: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/methimazole
- MLA
- “Methimazole: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/methimazole.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for methimazole on DailyMed (NIH) ↗.