Methimazole

A to Z Drug Facts

Methimazole

  Action
  Indications
  Contraindications
  Route/Dosage
  Interactions
  Lab Test Interferences
  Adverse Reactions
  Precautions
Patient Care Considerations
  Administration/Storage
  Assessment/Interventions
  Patient/Family Education


(meth-IMM-uh-zole)
Tapazole
Class: Antithyroid

 Action Inhibits synthesis of thyroid hormones.

 Indications Long-term therapy of hyperthyroidism; amelioration of hyperthyroidism in preparation for subtotal thyroidectomy or radioactive iodine therapy.

 Contraindications Use in nursing women.

 Route/Dosage

ADULTS: Initial dose: PO 15–60 mg/day in 3 equal doses at approximately 8-hr intervals. Maintenance: PO 5–15 mg/day. CHILDREN: Initial dose: PO 0.4 mg/kg/day. MAINTENANCE: PO Approximately ½ initial dose. Alternately, children may be given 0.5–0.7 mg/kg/day in 3 divided doses as initial therapy and 1/32/3 of initial dose for maintenance.

 Interactions

Anticoagulants: May decrease or increase anticoagulant action. Beta blockers: May increase effects of beta blockers, resulting in toxicity. Digoxin: May cause increase in effects of digitalis glycosides, including toxicity. Theophyllines: May alter theophylline clearance in hyperthyroid or hypothyroid patients.

 Lab Test Interferences None well documented.

 Adverse Reactions

CNS: Paresthesias; neuritis; headache; vertigo; drowsiness; neuropathies; NS stimulation; depression. DERM: Rash; urticaria; pruritus; erythema nodosum; skin pigmentation; xfoliative dermatitis; lupus-like syndrome including splenomegaly, hepatitis, periarteritis, hypoprothrombinemia and bleeding. EENT: Loss of taste; sialadenopathy. GI: Nausea; vomiting; epigastric distress. GU: Nephritis. HEPA: Jaundice; hepatitis. HEMA: Inhibition of myelopoiesis (eg, agranulocytosis, granulocytopenia, thrombocytopenia); aplastic anemia; hypoprothrombinemia; periarteritis. OTHER: Abnormal hair loss; arthralgia; myalgia; edema; lymphadenopathy; drug fever; interstitial pneumonitis; insulin autoimmune syndrome.

 Precautions

Pregnancy: Category D. Lactation: Avoid nursing. Agranulocytosis: Potentially most serious side effect. Discontinue drug in presence of agranulocytosis, aplastic anemia, hepatitis, fever or exfoliative dermatitis. Hemorrhage: May cause hypoprothrombinemia and bleeding. Monitor PT.


PATIENT CARE CONSIDERATIONS


 Administration/Storage

 Assessment/Interventions

OVERDOSAGE: SIGNS & SYMPTOMS
  Nausea, vomiting, epigastric distress, headache, fever, arthralgia, pruritus, edema, pancytopenia, agranulocytosis, exfoliative dermatitis, hepatitis, neuropathies, CNS stimulation or depression.

 Patient/Family Education

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© 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts