methimazole
Methimazole is a thyroid hormone synthesis inhibitor used to treat Goiter, Thyroid Crisis.
Thyroid Hormone Synthesis Inhibitor · by Aiping Pharm Inc
Generic of Tapazole
Key facts
- Active ingredient
- Methimazole
- Drug class
- Thyroid Hormone Synthesis Inhibitor
- Form
- Tablet
- Strength
- Methimazole 10MG · Methimazole 20MG · Methimazole 5MG
- Type
- Prescription (Rx)
- Brand or generic
- Generic
- May treat
- goiter, thyroid crisis
- Manufacturer
- Aiping Pharm Inc
- What the pharmacy pays
- ~$2.28 for 30 — not your price
- FDA application
- ANDA040547
What is Methimazole?
From the FDA label:Methimazole, USP (1-methylimidazole-2-thiol) is a white, crystalline substance that is freely soluble in water. It differs chemically from the drugs of the thiouracil series primarily because it has a 5- instead of a 6-membered ring. Methimazole tablet, USP contains 5 or 10 mg methimazole, an orally administered antithyroid drug. Each tablet also contains lactose monohydrate, magnesium stearate, potato starch and talc. The molecular weight is 114.17, and the molecular formula is C 4 H 6 N 2 S. The structural formula is as follows: Methimazole-Structural Formula
How to use
Methimazole tablets are administered orally. The total daily dosage is usually given in 3 divided doses at approximately 8-hour intervals. Adult - The initial daily dosage is 15 mg for mild hyperthyroidism, 30 to 40 mg for moderately severe hyperthyroidism, and 60 mg for severe hyperthyroidism, divided into 3 doses at 8-hour intervals. The maintenance dosage is 5 to 15 mg daily. Pediatric - Initially, the daily dosage is 0.4 mg/kg of body weight divided into 3 doses and given at 8-hour intervals. The maintenance dosage is approximately ½ of the initial dose.
Side effects
Major adverse reactions (which occur with much less frequency than the minor adverse reactions) include inhibition of myelopoiesis (agranulocytosis, granulocytopenia, thrombocytopenia, and aplastic anemia), drug fever, a lupus-like syndrome, insulin autoimmune syndrome (which can result in hypoglycemic coma), hepatitis (jaundice may persist for several weeks after discontinuation of the drug), periarteritis, and hypoprothrombinemia. Nephritis occurs very rarely. There have been postmarketing case reports of acute pancreatitis. There are reports of a vasculitis, often associated with the presence of anti-neutrophilic cytoplasmic antibodies (ANCA), resulting in severe complications [see WARNINGS ] . Minor adverse reactions include skin rash, urticaria, nausea, vomiting, epigastric distress, arthralgia, paresthesia, loss of taste, abnormal loss of hair, myalgia, headache, pruritus, drowsiness, neuritis, edema, vertigo, skin pigmentation, jaundice, sialadenopathy, and lymphadenopathy. To report SUSPECTED ADVERSE REACTIONS, contact AiPing Pharmaceutical, Inc. at 1-844-374-0016 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
Warnings
Important safety information
First Trimester Use of Methimazole and Congenital Malformations Methimazole crosses the placental membranes and can cause fetal harm, when administered in the first trimester of pregnancy. Rare instances of congenital defects, including aplasia cutis, craniofacial malformations (facial dysmorphism; choanal atresia), gastrointestinal malformations (esophageal atresia with or without tracheoesophageal fistula), omphalocele and abnormalities of the omphalomesenteric duct have occurred in infants born to mothers who received methimazole in the first trimester of pregnancy. If methimazole is used during pregnancy or if the patient becomes pregnant while taking this drug, the patient should be warned of the potential hazard to the fetus. Because of the risk for congenital malformations associated with use of methimazole in the first trimester of pregnancy, it may be appropriate to use other agents in pregnant women requiring treatment for hyperthyroidism. If methimazole is used, the lowest possible dose to control the maternal disease should be given. Agranulocytosis Agranulocytosis is potentially a life-threatening adverse reaction of methimazole therapy. Patients should be instructed to immediately report to their physicians any symptoms suggestive of agranulocytosis, such as fever or sore throat. Leukopenia, thrombocytopenia, and aplastic anemia (pancytopenia) may also occur. The drug should be discontinued in the presence of agranulocytosis or aplastic anemia (pancytopenia), and the patient’s bone marrow indices should be monitored. Liver Toxicity Although there have been reports of hepatotoxicity (including acute liver failure) associated with methimazole, the risk of hepatotoxicity appears to be less with methimazole than with propylthiouracil, especially in the pediatric population. Symptoms suggestive of hepatic dysfunction (anorexia, pruritus, right upper quadrant pain, etc.) should prompt evaluation of liver function (bilirubin, alkaline phosphatase) and hepatocellular integrity (ALT, AST). Drug treatment should be discontinued promptly in the event of clinically significant evidence of liver abnormality including hepatic transaminase values exceeding 3 times the upper limit of normal. Hypothyroidism Methimazole can cause hypothyroidism necessitating routine monitoring of TSH and free T4 levels with adjustments in dosing to maintain a euthyroid state. Because the drug readily crosses placental membranes, methimazole can cause fetal goiter and cretinism when administered to a pregnant woman. For this reason, it is important that a sufficient, but not excessive, dose be given during pregnancy [see PRECAUTIONS, Pregnancy ] . Vasculitis Cases of vasculitis resulting in severe complications have been reported in patients receiving methimazole therapy. These cases of vasculitis include: leukocytoclastic cutaneous vasculitis, acute kidney injury and glomerulonephritis, alveolar/pulmonary hemorrhage, CNS vasculitis, and neuropathy. Most cases were associated with anti-neutrophilic cytoplasmic antibodies (ANCA)-positive vasculitis. In some cases, vasculitis resolved/improved with drug discontinuation; however, more severe cases required treatment with additional measures including corticosteroids, immunosuppressant therapy, and plasmapheresis. If vasculitis is suspected, discontinue therapy and initiate appropriate intervention.
Who should not take Methimazole
Methimazole tablets are contraindicated in the presence of hypersensitivity to the drug or any of the other product components.
Overdose — what happens if you take too much
Signs and Symptoms Symptoms may include nausea, vomiting, epigastric distress, headache, fever, joint pain, pruritus, and edema. Aplastic anemia (pancytopenia) or agranulocytosis may be manifested in hours to days. Less frequent events are hepatitis, nephrotic syndrome, exfoliative dermatitis, neuropathies, and CNS stimulation or depression. No information is available on the median lethal dose of the drug or the concentration of methimazole in biologic fluids associated with toxicity and/or death. Treatment To obtain up-to-date information about the treatment of overdose, a good resource is your certified Regional Poison Control Center. In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in the patient. In the event of an overdose, appropriate supportive treatment should be initiated as dictated by the patient’s medical status.
U.S. Poison Control: call or text 1-800-222-1222 (free, 24/7). In an emergency call 911. From the FDA label; not medical advice.
Interactions
Anticoagulants (oral): Due to potential inhibition of vitamin K activity by methimazole, the activity of oral anticoagulants (e.g., warfarin) may be increased; additional monitoring of PT/INR should be considered, especially before surgical procedures. ß-adrenergic blocking agents: Hyperthyroidism may cause an increased clearance of beta blockers with a high extraction ratio. A dose reduction of beta-adrenergic blockers may be needed when a hyperthyroid patient becomes euthyroid. Digitalis glycosides: Serum digitalis levels may be increased when hyperthyroid patients on a stable digitalis glycoside regimen become euthyroid; a reduced dosage of digitalis glycosides may be needed. Theophylline: Theophylline clearance may decrease when hyperthyroid patients on a stable theophylline regimen become euthyroid; a reduced dose of theophylline may be needed.
Drug class
May treat (source: NIH RxClass)
Dosage forms
Tablet
The forms currently marketed in the U.S., per the FDA National Drug Code Directory.
Ways to save
Ask for the generic
Same active ingredient, far cheaper. Is there a generic? →
Request a 90-day supply
Bulk fills usually lower the per-dose price vs monthly refills.
Use copay cards
Manufacturer copay cards & patient-assistance programs — especially for brand drugs.
Compare alternatives
A same-class option may cost less. See alternatives →
Frequently asked questions
- What does Methimazole treat?
- Methimazole (Methimazole) may be used to treat goiter, thyroid crisis, based on NIH RxClass drug-classification data (conditions a drug may treat — not a verbatim copy of the FDA-approved label). This is general reference, not medical advice.
- How much does Methimazole cost?
- Nobody can tell you what you will pay — your price is set by your insurer's formulary, your deductible and the pharmacy's markup, and none of those are published. What IS published is what the pharmacy paid to acquire it: about $2.28 for 30, per the CMS NADAC survey. Treat that as the floor, not the quote — ask the pharmacist for the cash price as well as your copay, because for cheap generics the cash price often wins. Pharmacies pay less for a same-class option, Synthroid — about $1.83 on the same basis.
- Is there a coupon or discount for Methimazole?
- pharmaranks is an independent ratings site, not a pharmacy — we don't issue coupons or sell Methimazole. To pay less, Methimazole is already a generic — usually the lowest-cost version — so the main levers are comparing cash prices between pharmacies and using a pharmacy discount-card service. Prices vary by pharmacy, insurance, and location, so always confirm at the counter. This is general reference, not medical or financial advice.
- Who makes Methimazole?
- Methimazole is marketed by Aiping Pharm Inc. You can see Aiping Pharm Inc's full profile, rating, and other products on pharmaranks.
- Is Methimazole a brand-name or generic drug?
- Methimazole is a generic medication; its active ingredient is Methimazole. Generics contain the same active ingredient as the brand-name original and are usually lower cost.
- Is Methimazole available over the counter?
- No. Methimazole is a prescription (Rx) medication in the US — you need a prescription from a licensed clinician (in person or via telehealth); it isn't sold over the counter. For some conditions there are OTC alternatives — ask your pharmacist.
- What forms does Methimazole come in?
- Methimazole is currently marketed as tablet, per the FDA's National Drug Code Directory.
- What class of drug is Methimazole?
- Methimazole is classified as thyroid hormone synthesis inhibitor, per the FDA's Established Pharmacologic Class.
- Is Methimazole FDA-registered?
- Methimazole is on record with the U.S. FDA under application number ANDA040547. You can verify this on its official FDA label.
- Is Methimazole safe?
- There's no single safe-or-not verdict, and we don't yet have a composite recall-safety score for Methimazole. Review its FDA-label side effects and warnings below, and always consult a licensed professional.
- What are the side effects of Methimazole?
- Methimazole's side effects are taken directly from its FDA label. From the label: Major adverse reactions (which occur with much less frequency than the minor adverse reactions) include inhibition of myelopoiesis (agranulocytosis, granulocytopenia, thrombocytopenia, and aplastic anemia), drug fever, a lupus-like syndrome,… Both common and serious reactions are documented in full on this page. This is general reference from the FDA, not medical advice — always consult a professional.
Clinical content sourced from the FDA label via openFDA (U.S. FDA). View the FDA label on DailyMed → Provided for general reference only — not medical advice. Always consult a licensed professional and the current prescribing information.
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