Adult: In patients with Graves' disease or toxic multinodular goitre whom surgery or radioactive iodine therapy is inappropriate; to ameliorate hyperthyroid symptoms in preparation for radioactive iodine therapy or thyroidectomy: Mild cases: Initially, 15 mg daily. Moderately severe cases: Initially, 30-40 mg daily. Severe cases: Initially, 60 mg daily. All doses are given in 3 divided doses at 8-hour intervals. Maintenance dose: 5-15 mg daily. Dosage and treatment recommendations may vary among individual products and between countries (refer to specific product guidelines). Child: Initially, 0.4 mg/kg daily given in 3 divided doses at 8-hour intervals. Maintenance dose: 0.2 mg/kg daily. Dosage and treatment recommendations may vary among individual products and between countries (refer to specific product guidelines).
What are the brands available for Thiamazole in Philippines?
History of acute pancreatitis (after administration of thiamazole or carbimazole).
Special Precautions
Patient with or at risk for bone marrow suppression. Renal and hepatic impairment. Children. Pregnancy (particularly during the 1st trimester) and lactation.
Adverse Reactions
Significant: Severe dermatologic reactions, unexplained fever, hypothyroidism (prolonged use); leucopenia, thrombocytopenia, pancytopenia, aplastic anaemia; hypoprothrombinaemia, bleeding; vasculitis. Rarely, congenital anomalies (e.g. fetal goitre, cretinism, choanal atresia, aplasia cutis, facial dysmorphism). Blood and lymphatic system disorders: Lymphadenopathy. Gastrointestinal disorders: Nausea, vomiting, epigastric distress, loss of taste. General disorders and administration site conditions: Oedema. Hepatobiliary disorders: Jaundice. Musculoskeletal and connective tissue disorders: Myalgia, arthralgia. Nervous system disorders: Paraesthesia, drowsiness, headache, neuritis, vertigo. Skin and subcutaneous tissue disorders: Rash, pruritus, urticaria, alopecia, skin pigmentation. Potentially Fatal: Agranulocytosis, lupus-like syndrome, acute pancreatitis. Rarely, hepatotoxicity, including acute liver failure, fulminant hepatitis, hepatic necrosis, and hepatic encephalopathy.
May enhance the anticoagulant effect of oral anticoagulants (e.g. warfarin). May increase serum concentration of cardiac glycosides and theophylline derivatives.
Action
Description: Mechanism of Action: Thiamazole is a thioimidazole-derivative antithyroid drug which inhibits the production of thyroid hormones by blocking the oxidation of iodine in the thyroid glands. It also blocks the synthesis of thyroxine (T4) and triiodothyroxine (T3) but does not inactivate circulating T4 and T3. Synonym(s): Methimazole. Onset: 12-18 hours. Duration: 36-72 hours. Pharmacokinetics: Absorption: Readily and almost completely absorbed from the gastrointestinal tract. Bioavailability: Approx 93%. Time to peak plasma concentration: 1-2 hours. Distribution: Concentrated in the thyroid gland. Crosses the placenta and enters breastmilk. Volume of distribution: 0.66 L/kg. Metabolism: Metabolised in the liver. Excretion: Via urine (<10% as unchanged drug). Elimination half-life: 4-6 hours.
Chemical Structure
Thiamazole Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 1349907, Methimazole. https://pubchem.ncbi.nlm.nih.gov/compound/Methimazole. Accessed July 28, 2025.
H03BB02 - thiamazole ; Belongs to the class of sulfur-containing imidazole derivative agents. Used in the management of thyroid diseases.
References
Brayfield A, Cadart C (eds). Thiamazole. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 02/07/2025.Methimazole Tablet (Chartwell RX, LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 02/07/2025.Methimazole. Gold Standard Drug Database in ClinicalKey [online]. Elsevier Inc. https://www.clinicalkey.com. Accessed 23/07/2025.Methimazole. UpToDate Lexidrug, AHFS DI (Adult and Pediatric) Online. American Society of Health-System Pharmacists, Inc. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 02/07/2025.Methimazole. UpToDate Lexidrug, Pediatric and Neonatal Lexi-Drugs Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 02/07/2025.Thiamazole [Methimazole]. UpToDate Lexidrug, Lexi-Drugs Multinational Online. Waltham, MA. UpToDate, Inc. https://online.lexi.com. Accessed 02/07/2025.Timazol Tablet 5 mg (Imeks Pharma Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 02/07/2025.
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