methimazole (Rx)

Brand and Other Names:Northyx, Tapazole
  • Print

Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablet

  • 5mg
  • 10mg

Hyperthyroidism

Mild: 15 mg/day PO divided q8hr initially

Moderate: 30-40 mg/day PO divided q8hr initially

Severe: 60 mg/day PO divided q8hr initially

Maintenance: 5-30 mg/day PO divided q8hr

Graves Disease

10-20 mg/day PO once; after euthyroidism is achieved, reduce dosage by 50% and administer for 12-18 months; may subsequently taper or discontinue if TSH levels are normal

Thyrotoxicosis (Off-label)

15-20 mg PO q4hr during first day as adjunct to other agents; reduce frequency to qDay or q12hr once patient is stable

Orphan Designations

Brain metastases: Orphan designation (plus liothyronine) for brain metastases in patients with primary lung cancer

Glioblastoma mutiforme: Orphan designation (plus liothyronine) for treatment of glioblastoma multiforme

Sponsor

  • Musli Thyropeutics Ltd; 6 Hagefen Street, P. O. Box 529; Zur Moshe, Israel

Dosage Forms & Strengths

tablet

  • 5mg
  • 10mg

Hyperthyroidism

Initial: 0.5-0.7 mg/kg/day PO qDay or divided q8hr  

Maintenance: 0.2 mg/kg/day PO qDay or divided q8hr

Not to exceed 30 mg/day

Graves Disease

0.2-0.5 mg/kg/day PO; after euthyroidism is achieved, reduce dosage by 50% and administer for 1-2 years  

Thyrotoxicosis (Off-label)

0.5-1 mg/kg/day PO divided q8hr; adjust subsequent doses and duration of treatment based on patient response

Next:

Interactions

Interaction Checker

and methimazole

No Results

     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

            All Interactions Sort By:
             activity indicator 
            Previous
            Next:

            Adverse Effects

            Frequency Not Defined

            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

            Previous
            Next:

            Warnings

            Contraindications

            Hypersensitivity

            Breastfeeding

            Cautions

            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

            Previous
            Next:

            Pregnancy & 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)

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.

            Previous
            Next:

            Pharmacology

            Mechanism of Action

            Inhibits synthesis of thyroid hormone by blocking oxidation of iodine in thyroid gland; blocks synthesis of thyroxine (T4) and triiodothyronine (T3)

            Absorption

            Bioavailability: 80-95%

            Onset: PO, 12-18 hr

            Duration: 36-72 hr

            Peak plasma time: 1-2 hr

            Distribution

            Protein bound: None

            Metabolism

            Metabolized by liver

            Elimination

            Half-life: 4-6 hr

            Excretion: Urine

            Previous
            Next:

            Images

            Previous
            Next:

            Formulary

            FormularyPatient Discounts

            Adding plans allows you to compare formulary status to other drugs in the same class.

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

            Adding plans allows you to:

            • View the formulary and any restrictions for each plan.
            • Manage and view all your plans together – even plans in different states.
            • Compare formulary status to other drugs in the same class.
            • Access your plan list on any device – mobile or desktop.

            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
            Additional Offers
            Email to Patient

            From:

            To:

            The recipient will receive more details and instructions to access this offer.

            By clicking send, you acknowledge that you have permission to email the recipient with this information.

            Email Forms to Patient

            From:

            To:

            The recipient will receive more details and instructions to access this offer.

            By clicking send, you acknowledge that you have permission to email the recipient with this information.

            Previous
            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.