Methimazole Dosage
This dosage information may not include all the information needed to use Methimazole safely and effectively. See additional information for Methimazole.
The information at Drugs.com is not a substitute for medical advice. ALWAYS consult your doctor or pharmacist.
Usual Adult Dose for:
Usual Pediatric Dose for:
Additional dosage information:
Usual Adult Dose for Hyperthyroidism
Initial:
Mild hyperthyroidism: 5 mg orally every 8 hours.
Moderately severe hyperthyroidism: 10 mg orally every 8 hours (up to 40 mg per day).
Severe hyperthyroidism: 20 mg orally every 8 hours.
Maintenance:
5 to 15 mg orally daily.
Usual Pediatric Dose for Hyperthyroidism
Greater than or equal to 1 year:
Initial dose: 0.4 mg/kg/day orally in 3 equally divided doses 8 hours apart.
Maintenance dose: 0.2 mg/kg/day orally in 3 equally divided doses 8 hours apart.
Maximum dose: 30 mg/day.
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
Because methimazole is excreted in milk, the drug is contraindicated in nursing mothers.
Agranulocytosis is a potential side effect of methimazole treatment. Patients should be monitored closely and instructed to report any evidence of illness, particularly sore throat, skin eruptions, fever, headache, or general malaise. Leukopenia, thrombocytopenia and aplastic anemia may also occur. Methimazole should be discontinued in the presence of agranulocytosis, aplastic anemia, hepatitis or exfoliative dermatitis. Patients receiving methimazole should undergo monitoring of bone marrow function. Methimazole-induced agranulocytosis is generally associated with doses of 40 mg or more in persons older than 40 years of age.
Severe hepatic effects including rare reports of fulminant hepatitis, hepatic necrosis, encephalopathy, and death have been reported during methimazole therapy. Therefore, symptoms suggestive of hepatic dysfunction (anorexia, pruritis, right upper quadrant pain, etc.) should prompt evaluation of liver function. Treatment should be discontinued immediately if clinical evidence of liver abnormality including hepatic transaminase values exceeding 3 times the upper limit of normal.
Because methimazole may cause hypoprothrombinemia and bleeding, prothrombin time should be evaluated during therapy, especially before surgical procedures.
Periodic monitoring of thyroid function is necessary, and the finding of an elevated TSH warrants a decrease in the dosage of methimazole.
Dialysis
Not dialyzable.
Other Comments
Methimazole has been given as a once daily dose in the morning.
