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Methimazole

    Brands

    DEA Class; Rx

    Common Brand Names; Northyx, Tapazole

    • Antithyroid Agents

    Oral thioimidazole antithyroid agent; lower risk of hepatotoxicity when compared to propylthiouracil (PTU)
    Used for hyperthyroid conditions including Graves disease in both adult and pediatric patients
    Do not use in early pregnancy

    Indicated for the treatment of thyrotoxicosis, including hyperthyroidism, Graves’ disease, toxic multinodular goiter, and thyroid storm.
    For the treatment of thyroid storm.

    Hypersensitivity

    Breastfeeding

    Agranulocytosis

    Alopecia

    Aplastic anemia

    Dermatologic reactions (eg, rash, pruritus, skin pigmentation)

    Hepatotoxicity

    Leukocytoclastic vasculitis

    Neuritis

    Polyarthritis

    Pruritus

    Salivary gland swelling

    Skin pigmentation

    Thrombocytopenia

    Urticaria

    Vertigo

    Lupus-like syndrome reported

    Hypoprothrombinemia and bleeding may occur; monitor, especially before surgical procedure performed

    Antineutrophil cytoplasmic autoantibody (ANCA)-positive vasculitis reported; discontinue use in presence of vasculitis

    Concurrent administration of other agranulocytosis-causing drugs

    Prolonged treatment may cause hypothyroidism; routinely monitor free T4 levels and TSH; adjust dose as necessary to maintain euthyroid state

    Significant bone marrow suppression may occur; use caution if administered with other agents known to cause myelosupression; discontinue if significan agranulocytosis, leukopenia, or aplastic anemia occurs

    Hepatitis reported; discontinue if it occurs or if clinically significant hepatic enzyme levels, including transaminases >3 times upper limit of normal observed

    Discontinue if unexplained fever occurs

    Antithyroid agents associated with rare but severe dermatologic reactions; discontinue if exfoliative dermatitis occurs

    Pregnancy category: D (drug crosses placenta)

    Lactation: Drug distributed in breast milk; use contraindicated by manufacturer (American Academy of Pediatrics [AAP] Committee states that drug is compatible with nursing; American Academy of Family Physicians [AAFP] states that it is safe for nursing)

    Adults

    60 mg/day PO.

    Geriatric

    60 mg/day PO.

    Adolescents

    0.4 mg/kg/day PO is the FDA-approved dose; however, doses up to 1 mg/kg/day PO (Max: 30 mg) have been used off-label.

    Children

    0.4 mg/kg/day PO is the FDA-approved dose; however, doses up to 1 mg/kg/day PO (Max: 30 mg) have been used off-label.

    Infants

    0.4 mg/kg/day PO is the FDA-approved dose; however, doses up to 1 mg/kg/day PO have been used off-label.

    Neonates

    Safety and efficacy have not been established; however, doses up to 1 mg/kg/day PO have been used off-label.

    Methimazole

    tablet

    • 5mg
    • 10mg