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Methimazole

Mucavo, Perizol, Thyromazol · ATC code H03BB02

Also known as: Thiamazol, Tiamazol

Key facts
Active substance
Methimazole
Drug class
Antithyroid agent
ATC code
H03BB02
Authorisation
authorised nationally; no central EU authorisation
Information as of
2026-10-29

Key facts

Methimazole is an antithyroid drug. Per the US prescribing information, it is used for hyperthyroidism due to Graves' disease or toxic multinodular goiter.

What it is used for

  • Graves' disease with hyperthyroidism or toxic multinodular goiter when surgery or radioactive iodine is not appropriate
  • Amelioration of hyperthyroid symptoms in preparation for thyroidectomy or radioactive iodine therapy

Dosing

  • Oral; total daily dosage usually in 3 divided doses at approximately 8-hour intervals
  • Adults, initial daily dosage: 15 mg for mild, 30 to 40 mg for moderately severe and 60 mg for severe hyperthyroidism
  • Maintenance 5 to 15 mg daily
  • Children: initially 0.4 mg/kg body weight daily in 3 doses, maintenance about half of the initial dose

Contraindications

  • Hypersensitivity to methimazole or any other product component

Important warnings

  • First-trimester use can cause congenital malformations (e.g. aplasia cutis, craniofacial and gastrointestinal malformations, omphalocele); other agents may be appropriate in pregnancy
  • Agranulocytosis, potentially life-threatening; report fever or sore throat immediately; discontinue in agranulocytosis or aplastic anemia
  • Hepatotoxicity including acute liver failure; evaluate liver function if symptoms of hepatic dysfunction occur
  • Vasculitis, often ANCA-associated, with severe complications

Side effects

  • Major (less frequent): agranulocytosis, thrombocytopenia, aplastic anemia, drug fever, lupus-like syndrome, insulin autoimmune syndrome, hepatitis, hypoprothrombinemia; acute pancreatitis reported
  • Minor: skin rash, urticaria, nausea, vomiting, arthralgia, myalgia, paresthesia, loss of taste, hair loss, headache, pruritus, drowsiness, edema

Interactions

  • Oral anticoagulants (e.g. warfarin): activity may be increased; consider additional PT/INR monitoring
  • Beta-blockers and digitalis glycosides: dose reduction may be needed once the patient becomes euthyroid

Pregnancy and breastfeeding

  • Crosses the placenta; risk of malformations in the first trimester; if used, the lowest possible dose
  • Present in breast milk; several studies found no effect on nursing infants

Summary of the official product information, written with AI on 2026-10-29. Every number was checked automatically against the original text. Not reviewed by a physician – the full official text is authoritative.

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For patients

Patient information (US)

This product has no separate US patient information.

Authorisation and brand names by country

Medicines with exactly this active-substance composition, as listed in the national registers – alphabetical and without ranking. Whether a product is currently available is not shown here.

Turkey

  • MucavoWORLD MEDICINE İLAÇ SAN. VE TİC. A.Ş. · 3 register entries
  • PerizolMERCK İLAÇ ECZA VE KİMYA TİC. A.Ş. · 8 register entries
  • ThyromazolABDİ İBRAHİM İLAÇ SAN. VE TİC. A.Ş. · 7 register entries

Source: TİTCK – Ruhsatlı Beşeri Tıbbi Ürünler Listesi, as of 2026-10-16

Medelix receives no money from pharmaceutical companies. Brand names are listed alphabetically and without ranking.

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Sources

  1. U.S. Food and Drug Administration. Methimazole (AiPing Pharmaceutical, Inc.) – Prescribing Information, 2026-08-20. DailyMed (NLM), 2026-10-29. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=06bb4bcc-5e47-48b6-a76c-648f846704e8
  2. TİTCK – Ruhsatlı Beşeri Tıbbi Ürünler Listesi, 2026-10-16. https://www.titck.gov.tr/dinamikmodul/85
  3. Wikidata (CC0): ATC H03BB.

Editorial: Medelix editorial team · last updated 2026-10-29 · How these pages are made · Report an error

Source: U.S. Food and Drug Administration (FDA), prescribing information, via DailyMed (NLM); public domain. Not advertising, not a treatment recommendation. For questions about your own treatment, ask your doctor or pharmacist.