Methimazole: Generic, Uses, Side Effects, Dosages, Interactions, Warnings (2023)

  • Uses
    • What Is Methimazole and How Does It Work?
  • Dosage
    • What Are Dosages of Methimazole?
  • Side Effects
    • What Are Side Effects Associated with Using Methimazole?
  • Drug Interactions
    • What Other Drugs Interact with Methimazole?
  • Warnings and Precautions
    • What Are Warnings and Precautions for Methimazole?

What Is Methimazole and How Does It Work?

Methimazole is used to treat overactive thyroid (hyperthyroidism). It works by stopping the thyroid gland from making too much thyroid hormone.

  • Methimazole is available under the following different brand names: Northyx, and Tapazole.

What Are Dosages of Methimazole?

Dosages of Methimazole:

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Adult and Pediatric Dosage Forms and Strengths


  • 5 mg
  • 10 mg

Dosing Considerations – Should be Given as Follows:



  • Mild: 15 mg/day orally divided every 8 hours initially
  • Moderate: 30-40 mg/day orally divided every 8 hours initially
  • Severe: 60 mg/day orally divided every 8 hours initially
  • Maintenance: 5-15 mg/day orally divided every 8 hours


  • Initial: 0.4-0.7 mg/kg/day orally divided every 8 hours
  • Maintenance: 1/3-2/3 of initial orally dosage divided every 8 hours orally
  • Not to exceed 30 mg/day

Graves Disease

  • Adult: 10-20 mg/day orally; after euthyroidism is achieved, reduce dosage by 50% and administer for 12-18 months
  • Pediatric: 0.2-0.5 mg/kg/day orally; after euthyroidism is achieved, reduce dosage by 50% and administered for 1-2 years

Thyrotoxic Crisis

  • 20-30 mg every 6-12 hours for the short term, then reduce dosage to maintenance (5-15 mg/day) or reduce the frequency to every 12 hours or every 24 hours
Methimazole: Generic, Uses, Side Effects, Dosages, Interactions, Warnings (1)


Where is the thyroid gland located? See Answer

What Are Side Effects Associated with Using Methimazole?

Common side effects of methimazole include:

Rare but serious side effects of methimazole include:

  • Yellowing eyes/skin (jaundice)
  • Dark urine
  • Severe stomach or abdominal pain
  • Persistent nausea or vomiting
  • Changes in the amount of urine

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Methimazole?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

(Video) methimazole

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

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What Are Warnings and Precautions for Methimazole?


This medication contains methimazole. Do not take Northyx or Tapazole if you are allergic to methimazole or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately


  • Hypersensitivity
  • Breastfeeding

Short-Term Effects

  • See "What Are Side Effects Associated with Using Methimazole?"

Long-Term Effects

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  • See "What Are Side Effects Associated with Using Methimazole?"


  • Liver disease
  • Hepatic reactions may occur
  • Pregnancy
  • Lupus-like syndrome reported
  • Antineutrophil cytoplasmic autoantibody (ANCA)-positive vasculitis reported
  • Dosage greater than 40 mg/day
  • Patient age greater than 40 years
  • Concurrent administration of other agranulocytosis-causing drugs
  • Risk of rare but serious agranulocytosis, cholestatic jaundice, and rare congenital abnormalities (propylthiouracil [PTU] preferred in pregnancy)
  • Prolonged treatment may cause hypothyroidism
  • Discontinue if agranulocytosis, pancytopenia, hepatitis, fever, or exfoliative dermatitis occurs
  • 10 times more potent than PTU, but action may be less consistent
  • High rate of relapse (more likely in smokers)

Pregnancy and Lactation

  • Use methimazole during pregnancy only in LIFE-THREATENING emergencies when no safer drug is available
  • Methimazole crosses the placenta
  • There is positive evidence of human fetal risk
  • Methimazole is distributed in breast milk
  • Its use is contraindicated by the manufacturer
  • The American Academy of Pediatrics (AAP) Committee states that methimazole is compatible with nursing
  • The American Academy of Family Physicians (AAFP) states that it is safe for nursing
Methimazole: Generic, Uses, Side Effects, Dosages, Interactions, Warnings (2)


Hyperthyroidism Symptoms and Treatment See Slideshow


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Medscape. Methimazole.
RxList. Tapazole Side Effects Center.


What are the side effects of taking methimazole? ›

Methimazole may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
  • skin rash.
  • itching.
  • abnormal hair loss.
  • upset stomach.
  • vomiting.
  • loss of taste.
  • abnormal sensations (tingling, prickling, burning, tightness, and pulling)
  • swelling.
Jul 15, 2017

What is the generic for methimazole? ›

Tapazole is a prescription medicine used to treat the symptoms of Hyperthyroidism (overactive thyroid) and Graves Disease. Tapazole may be used alone or with other medications. Tapazole belongs to a class of drugs called Antithyroid Agents.

What should you not take with thyroid medication? ›

Don't take calcium supplements or antacids at the same time you take thyroid hormone replacement. Take any products containing calcium at least four hours before or after taking thyroid hormone replacement.

Why is methimazole a hazardous drug? ›

Methimazole has been classified as hazardous because the medication impedes the body from using iodine to make thyroid hormone, thereby inhibiting synthesis of the hormone. The drug may cause birth defects and has been found to cause cancer in rodents.

Can you drink coffee while taking methimazole? ›

In studies, coffee reduced the body's absorption of thyroid medications by about 30%. That's why experts recommend that you wait at least 60 minutes between drinking coffee and taking thyroid medication.

Does methimazole affect blood pressure? ›

Methimazole treatment reduces cardiac hypertrophy and mortality without a concomitant reduction in blood pressure in established Goldblatt two-kidney one clip hypertension. Experientia.

What should I monitor with methimazole? ›

Methimazole can cause hypothyroidism. [6] Therefore it is crucial to monitor T3 T4 levels in the serum, to adjust the dose to maintain a euthyroid state. In addition, since it crosses the placenta readily, it is capable of causing hypothyroidism and cretinism in newborns.

Can methimazole affect your heart? ›

Maladaptive hypertrophic and fibrotic myocardial remodeling in advanced heart failure can predispose a patient to a spectrum of ventricular arrhythmias [1]. Discontinuation of medications such as methimazole in a patient with advanced heart failure can further increase the risk for ventricular arrhythmias.

Does methimazole cause anxiety? ›

Moreover, TRH caused mild or moderate 'anxiety or nervousness' in only 18% of controls and 25% of patients.

Is methimazole hard on liver? ›

Methimazole is also capable of causing clinically apparent, idiosyncratic liver injury. The onset of hepatotoxicity is usually within 2 to 12 weeks of starting and the pattern of enzyme elevations is typically cholestatic or mixed, although hepatocellular patterns have also been described.

Does methimazole damage the thyroid? ›

This medicine may cause hypothyroidism (low levels of thyroid hormone in the blood).

Does methimazole destroy the thyroid? ›

The main advantage of using ATD in GH is the fact that this treatment does not destroy thyroid tissue and once remission is achieved, many patients continue to have normal thyroid function without any treatment.

What is the difference between methimazole and methimazole? ›

Thiamazole and methimazole are the same chemical. Thiamazole is the international nonproprietary name (INN) while methimazole is the United States adopted name (USAN). Thiamazole is a thioamide used to treat hyperthyroidism such as in Graves' disease.

What a thyroid patient should not drink? ›

Alcohol appears to have a toxic effect on the thyroid gland and suppresses the ability of the body to use thyroid hormone. Ideally, people with hypothyroidism should cut out alcohol completely or drink in careful moderation.

What medications should be avoided with hyperthyroidism? ›

The most commonly implicated drugs are amiodarone and lithium, and thyroid function should be monitored closely. Amiodarone is known to have complex effects on thyroid function owing to its high iodine content. It has been implicated in causing both hyperthyroidism and hypothyroidism.

Can I take vitamin D with methimazole? ›

Interactions between your drugs

No interactions were found between methimazole and Vitamin D3.


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