Methimazole
(Thiamazole)
Methimazole (Tapazole)
Thiamazole (Tapazole)
Methimazole
(meth- IM-ah-zohl)
Pregnancy Category: D Tapazole (Rx)

Classification: Antithyroid drug

See Also: See also Antithyroid Drugs .

Action/Kinetics: Onset is more rapid but effect is less consistent than that of propylthiouracil. Bioavailability may be affected by food. t 1/2: 4-14 hr. Onset: 10-20 days. Time to peak effect: 2-10 weeks. t 1/2: 6-13 hr. Crosses the placenta; high levels appear in breast milk. Metabolized in the liver and excreted through the kidneys (7% unchanged).

Special Concerns: Incidence of hepatic toxicity may be greater than for propylthiouracil.

How Supplied: Tablet: 5 mg, 10 mg

Dosage
?Tablets Mild hyperthyroidism.
Adults, initial: 15 mg/day.
Moderately severe hyperthyroidism.
Adults, initial: 30-40 mg/day.
Severe hyperthyroidism.
Adults, initial: 60 mg/day. For hyperthyroidism, the daily dose is usually given in three equal doses 8 hr apart. Maintenance: 5-15 mg/day as a single dose or divided into two doses. Pediatric: 0.4 mg/kg given once daily or divided into two doses; maintenance: 0.2 mg/kg. Alternatively, initial: 0.5-0.7 mg/kg/day (15-20 mg/m ²/day in three divided doses); maintenance: 1/3- 2/3 initial dose when client is euthyroid up to a maximum of 30 mg/day.
Thyrotoxic crisis.
Adults, 15-20 mg/4 hr during the first day as an adjunct to other treatments.