methimazole


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Related to methimazole: propylthiouracil, Carbimazole

methimazole

 [meth-im´ah-zōl]
a thyroid inhibitor used in treatment of hyperthyroidism.

methimazole

Apo-Methimazole (CA), Tapazole

Pharmacologic class: Thiomidazole derivative

Therapeutic class: Antithyroid drug

Pregnancy risk category D

Action

Directly interferes with thyroid synthesis by preventing iodine from combining with thyroglobulin, leading to decreased thyroid hormone levels

Availability

Tablets: 5 mg, 10 mg

Indications and dosages

Mild hyperthyroidism

Adults and adolescents: Initially, 15 mg P.O. daily in three equally divided doses at approximately 8-hour intervals. For maintenance, 5 to 15 mg/day in equally divided doses at approximately 8-hour intervals.

Children: Initially, 0.4 mg/kg/day in three divided doses at 8-hour intervals. For maintenance, approximately 0.2 mg/kg/day in three divided doses at 8-hour intervals.

Moderate hyperthyroidism

Adults and adolescents: Initially, 30 to 40 mg P.O. daily in three equally divided doses at approximately 8-hour intervals. For maintenance, 5 to 15 mg/day in three equally divided doses at approximately 8-hour intervals.

Children: 0.4 mg/kg/day P.O. as a single dose or in divided doses at 8-hour intervals. For maintenance, approximately 0.2 mg/kg/day as a single dose or in three divided doses at 8-hour intervals.

Severe hyperthyroidism

Adults and adolescents: Initially, 60 mg/day P.O. in three equally divided doses at approximately 8-hour intervals. For maintenance, 5 to 15 mg/day in three equally divided doses at approximately 8-hour intervals.

Children: Initially, 0.4 mg/kg/day P.O. as a single dose or in three divided doses at 8-hour intervals. For maintenance, approximately 0.2 mg/kg/day as a single dose or in three divided doses at 8-hour intervals.

Contraindications

• Hypersensitivity to drug

• Breastfeeding

Precautions

Use cautiously in:

• bone marrow depression

• patients older than age 40

• pregnant patients.

Administration

• Give with meals as needed to reduce GI upset.

Adverse reactions

CNS: headache, vertigo, paresthesia, neuritis, depression, neuropathy, CNS stimulation

GI: nausea, vomiting, constipation, epigastric distress, ileus, salivary gland enlargement, dry mouth, anorexia

GU: nephritis

Hematologic: thrombocytopenia, agranulocytosis, leukopenia, aplastic anemia

Hepatic: jaundice, hepatic dysfunction, hepatitis

Metabolic: hypothyroidism

Musculoskeletal: joint pain, myalgia

Skin: rash, urticaria, skin discoloration, pruritus, erythema nodosum, exfoliative dermatitis, abnormal hair loss

Other: fever, lymphadenopathy, lupuslike syndrome

Interactions

Drug-drug. Aminophylline, oxtriphylline, theophylline: decreased clearance of both drugs

Amiodarone, iodine, potassium iodide: decreased response to methimazole

Anticoagulants: altered requirements for both drugs

Beta-adrenergic blockers: altered beta blocker clearance

Digoxin: increased digoxin blood level

Drug-diagnostic tests. Granulocytes, hemoglobin, platelets, white blood cells: decreased values

Patient monitoring

• Check for agranulocytosis in patients older than age 40 and in those receiving more than 40 mg/day.

• Assess hematologic studies. Agranulocytosis usually occurs within first 2 months of therapy and is rare after 4 months.

• Monitor thyroid function tests periodically. Once hyperthyroidism is controlled, elevated thyroid-stimulating factor indicates need for dosage decrease.

• Assess liver function tests and check for signs and symptoms of hepatic dysfunction.

• Monitor patient for fever, sore throat, and other evidence of infection as well as for unusual bleeding or bruising.

• Assess patient for signs and symptoms of hypothyroidism, such as hard edema of subcutaneous tissue, drowsiness, slow mentation, dryness or loss of hair, decreased temperature, hoarseness, and muscle weakness.

Patient teaching

• Tell patient to take with meals if GI upset occurs.

• Advise patient to take exactly as prescribed to maintain constant blood level.

• Tell patient to report rash, fever, sore throat, unusual bleeding or bruising, headache, rash, yellowing of skin or eyes, abdominal pain, vomiting, or flulike symptoms.

• Caution female patient not to breastfeed while taking drug.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.

methimazole

/meth·im·a·zole/ (meth-im´ah-zōl) a thyroid inhibitor used in the treatment of hyperthyroidism.

methimazole

(mə-thĭm′ə-zōl′)
n.
A drug, C4H6N2S, that inhibits the synthesis of thyroid hormone and is used to treat hyperthyroidism.

methimazole

[məthim′əzōl]
an orally administered antithyroid drug.
indication It is prescribed in the treatment of hyperthyroidism.
contraindications Use in nursing mothers, because it is excreted in milk, and known hypersensitivity to the drug prohibit its use.
adverse effects Agranulocytosis, leukopenia, thrombocytopenia, and aplastic anemia may occur.

methimazole

A drug used in the treatment of overactivity of the thyroid gland. It is effective in reducing thyroid activity but may cause AGRANULOCYTOSIS. A sore throat is a warning symptom.

methimazole

a thiourea antithyroid drug used in the treatment of feline hyperthyroidism.
References in periodicals archive ?
Two antithyroid medications are currently available: methimazole (Tapazole[R]) and propylthiouracil (PTU).
The Cornell College of Veterinary Medicine invites New York cat owners and their veterinarians with clinically affected cats who are newly diagnosed or hard to control on methimazole, to consider enrolling in this study.
The rate of relapse of hyperthyroidism in patients consuming PTU (propyl-thiouracil) was 64% (18 out of 28 patients) and for patients consuming methimazole was 52% (124 out of 240) which was not statistically significant (P=0.
She noticed that her energy level improved, the dosage of methimazole needed to control her thyroid level was able to be titrated down, her migraines lessened, and chronic pain issues improved.
It used to be that propylthiouracil (PTU) or methimazole could be used interchangeably, but there's now good evidence that there's a very serious hepatic necrosis associated with PTU; it's rare, but it's not at all associated with methimazole," she said.
WASHINGTON -- Given growing concerns about propylthiouracil-related liver toxicity, "it may be that we should be weighing the relative risks" of this drug and methimazole for the treatment of Graves' disease during pregnancy, Dr.
04% methimazole (Sigma, USA) in drinking water for consecutive 14 days (Isman et al.
Contributing to URL/Mutual's successes has been the recent introduction of 10 new generic drugs, including seven from Mutual--clonidine, cyclobenzaprine, folic acid, primidone, zonisamide, lovastatin and meloxicam--and three more made by other manufacturers--glycoprolate, methimazole and pramoxine hydrochloride 1%.
The treatment of Graves' thyrotoxicosis includes the use of antithyroid drugs (ATD), such as methimazole, carbimazole, and propyltiouracile; destructive therapy with radioactive iodine; and thyroid surgery.
Serum thyroid-stimulating antibody, thyroglobulin levels, and thyroid suppressibility measurement as predictors of the outcome of combined methimazole and triiodothyronine therapy in Graves' disease.