methimazole(redirected from Apo-Methimazole)
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Apo-Methimazole (CA), Tapazole
Pharmacologic class: Thiomidazole derivative
Therapeutic class: Antithyroid drug
Pregnancy risk category D
Directly interferes with thyroid synthesis by preventing iodine from combining with thyroglobulin, leading to decreased thyroid hormone levels
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.
• Hypersensitivity to drug
Use cautiously in:
• bone marrow depression
• patients older than age 40
• pregnant patients.
• Give with meals as needed to reduce GI upset.
CNS: headache, vertigo, paresthesia, neuritis, depression, neuropathy, CNS stimulation
GI: nausea, vomiting, constipation, epigastric distress, ileus, salivary gland enlargement, dry mouth, anorexia
Hematologic: thrombocytopenia, agranulocytosis, leukopenia, aplastic anemia
Hepatic: jaundice, hepatic dysfunction, hepatitis
Musculoskeletal: joint pain, myalgia
Skin: rash, urticaria, skin discoloration, pruritus, erythema nodosum, exfoliative dermatitis, abnormal hair loss
Other: fever, lymphadenopathy, lupuslike syndrome
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
• 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.
• 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.
methimazoleA 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.
n brand name: Tapazole;
drug class: thyroid hormone antagonist;
action: inhibits synthesis of thyroid hormones by decreasing iodine use in manufacture of thyroglobulin and iodothyronine;
uses: hyperthyroidism, preparation for thyroidectomy, thyrotoxic crisis, thyroid storm.