Classes
DEA Class; Rx
Common Brand Names; Northyx, Tapazole
- Antithyroid Agents
Description
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
Indications
Contraindications
Hypersensitivity
Breastfeeding
Adverse Effects
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
Warnings
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 and Lactation
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)
Maximum Dosage
60 mg/day PO.
60 mg/day PO.
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.
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.
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.
Safety and efficacy have not been established; however, doses up to 1 mg/kg/day PO have been used off-label.
How supplied
Methimazole
tablet
- 5mg
- 10mg