Methimazole Dosage

Medically reviewed by Drugs.com. Last updated on Aug 14, 2023.

Usual Adult Dose for Hyperthyroidism

Initial dose:
Mild hyperthyroidism: 15 mg orally per day
Moderately severe hyperthyroidism: 30 to 40 mg orally per day
Severe hyperthyroidism: 60 mg orally per day

Maintenance dose:
5 to 15 mg orally per day

Comments: Daily doses are usually given in 3 divided doses at approximately 8 hour intervals

Uses:

• For the treatment of Graves' disease with hyperthyroidism or toxic multinodular goiter in whom surgery or radioactive iodine therapy is not an appropriate treatment option.
• To ameliorate symptoms of hyperthyroidism in preparation for thyroidectomy or radioactive iodine therapy.

Usual Pediatric Dose for Hyperthyroidism

Initial dose: 0.4 mg/kg orally per day

Maintenance dose: 0.2 mg/kg orally per day (approximately half the initial dose)

Comments: Daily doses are usually given in 3 divided doses at approximately 8 hour intervals

Renal Dose Adjustments

Data not available

Liver Dose Adjustments

Data not available

Dose Adjustments

An elevated TSH, during periodic monitoring of thyroid function, should lead to a decrease in the dosage of methimazole.

Precautions

CONTRAINDICATIONS:

• Hypersensitivity to the active substance or any product excipients

Consult WARNINGS section for additional precautions.

Dialysis

Data not available

Other Comments

Administration advice:

• Take orally in equally divided doses at approximately 8-hour intervals

General:

• Patients treated with this drug should be under close surveillance due to the potential for serious adverse effects.
• Avoid use during the first trimester of pregnancy due to reports of fetal abnormalities; after the first trimester it may be preferable to switch to methimazole due to hepatotoxicity of propylthiouracil.

Monitoring:

• Routine monitoring of TSH and free T4 levels is necessary to avoid under or over treatment
• Consider monitoring prothrombin time if there are concerns of bleeding; prothrombin time should be monitored before surgical procedures
• Obtain complete blood counts if there are signs and symptoms of agranulocytosis
• Perform liver function testing if there are any symptoms of hepatic dysfunction

Patient advice:

• Patients should understand the importance of contacting their healthcare provider promptly if they experience any signs or symptoms of liver dysfunction, low blood counts, bleeding, or vasculitis.
• Women should be instructed to speak to their healthcare provider if they are pregnant or plan to become pregnant.

Frequently asked questions

• Does methimazole cause hair loss?

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer