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Indications & Uses
Tapazol is indicated for:
Pharmacology
Methimazole works by stopping the thyroid from making new thyroid hormones, and that is why it helps in hyperthyroidism. It has no effect on the thyroxine and triiodothyronine already stored in the thyroid or circulating in the blood. It also doesn't interfere with thyroid hormones given by mouth or by injection, which keep working as they normally would.
The body takes up methimazole readily from the gastrointestinal tract. The liver metabolizes it, and it leaves the body in the urine.
Dosage Reference
Reference Information Only
Dosages shown are general references from official sources. Always consult your doctor or pharmacist for personalized dosing.
Adults:
Methimazole is taken by mouth. The total daily dose is usually split into 3 doses, given about 8 hours apart.
Adults: The starting daily dose is 15 mg for mild hyperthyroidism, 30 to 40 mg for moderately severe hyperthyroidism, and 60 mg for severe hyperthyroidism. Each of these is divided into 3 doses at 8 hour intervals. The maintenance dose is 5 to 15 mg daily.
Children: The starting daily dose is 0.4 mg/kg of body weight, divided into 3 doses and given at 8 hour intervals. The maintenance dose is about 1/2 of the starting dose.
Use in children and adolescents: Severe liver injury has been reported after marketing in pediatric patients treated with propylthiouracil. For this reason, Methimazole is the preferred choice when a child or adolescent needs an antithyroid drug.
Side Effects
Common side effects of methimazole are 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. Rare side effects include agranulocytosis, granulocytopenia, thrombocytopenia and aplastic anemia, drug fever, a lupus-like syndrome, and insulin autoimmune syndrome (which can result in hypoglycemic coma). Hepatitis can also occur, and jaundice may persist for several weeks after methimazole is stopped. Periarteritis and hypoprothrombinemia are among the rare effects too. Nephritis occurs very rarely.
Cautions & Contraindications
Warnings & Precautions
Congenital Malformations Methimazole crosses the placenta easily and can harm the baby, especially when it is taken in the first trimester of pregnancy. If a woman uses it during pregnancy, or becomes pregnant while taking it, she should be warned about the possible risk to the baby. Some birth defects have been reported in children of patients treated with Methimazole, so other medicines may be more suitable for pregnant women who need treatment for hyperthyroidism, particularly in the first trimester. If Methimazole is used, the dose should be the lowest one that controls the disease. Agranulocytosis Agranulocytosis can be a life-threatening reaction to Methimazole treatment. Patients should be told to report to their doctor immediately if they get symptoms that may point to it, such as fever or sore throat. Leukopenia, thrombocytopenia and aplastic anemia (pancytopenia) may also occur. The medicine should be stopped if agranulocytosis, aplastic anemia (pancytopenia), ANCA-positive vasculitis, hepatitis or exfoliative dermatitis is present, and the patient's bone marrow indices should be monitored. Liver Toxicity Liver toxicity has been reported with Methimazole. The risk seems lower than with propylthiouracil, though, especially in children. Treatment should be stopped promptly if there is clinically significant evidence of a liver abnormality, including hepatic transaminase values above 3 times the upper limit of normal. Hypothyroidism Methimazole can cause hypothyroidism, so TSH and free T4 levels need routine monitoring, and the dose should be adjusted to keep the patient euthyroid. Because the drug crosses the placenta easily, it can cause fetal goiter and cretinism when given to a pregnant woman. For this reason, the dose during pregnancy should be enough to control the disease but not more than that. The medicine may also cause hypoprothrombinemia and bleeding, so prothrombin time should be monitored during treatment, especially before surgical procedures. Thyroid function tests should be checked periodically as well. Once the clinical signs of hyperthyroidism have settled, a rising serum TSH means a lower maintenance dose should be used.
Contraindications
Don't give Methimazole to anyone who is hypersensitive (allergic) to the medicine itself or to any of the other ingredients in the product.
Pregnancy & Breastfeeding
Methimazole is Pregnancy Category D. Congenital malformations linked to its use are rare, but because of them other medicines may be the better choice for pregnant women who need treatment for hyperthyroidism, particularly in the first trimester.
Methimazole passes into breast milk. Even so, several studies found no effect on the clinical status of nursing infants whose mothers were taking it, especially when the infant's thyroid function was checked often (weekly or biweekly).
⚠️ Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.
Overdose
An overdose of methimazole can cause nausea, vomiting, discomfort in the upper stomach (epigastric distress), headache, fever, joint pain, itching and swelling (edema). Aplastic anemia or agranulocytosis may show up within hours to days. Less often, people develop hepatitis, nephrotic syndrome, exfoliative dermatitis, neuropathies, or either stimulation or depression of the CNS. If an overdose happens, start supportive treatment suited to the patient's medical condition.
⚠️ In an emergency call 999 or go to the nearest hospital emergency department.
Storage
Keep Methimazole in a cool, dry place below 30°C, away from light and out of children's reach.
Drug Interactions
Common questions about Tapazol 5 mg
What is Tapazol 5 mg Tablet?
Tapazol 5 mg Tablet is a medicine that contains Methimazole. It is made by Renata PLC. It belongs to the Anti-thyroid drugs group of medicines.
What is Tapazol used for?
Tapazol is used for: Hyperthyroidism.
What are the side effects of Tapazol?
Common side effects of methimazole are 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. Rare side effects include agranulocytosis, granulocytopenia, thrombocytopenia and aplastic anemia, drug fever, a lupus-like syndrome, and insulin autoimmune syndrome (which can result in hypoglycemic coma).
Can I take Tapazol during pregnancy or while breastfeeding?
Methimazole is Pregnancy Category D. Congenital malformations linked to its use are rare, but because of them other medicines may be the better choice for pregnant women who need treatment for hyperthyroidism, particularly in the first trimester. Talk to your doctor before taking any medicine during pregnancy or while breastfeeding.
What happens if I take too much Tapazol?
An overdose of methimazole can cause nausea, vomiting, discomfort in the upper stomach (epigastric distress), headache, fever, joint pain, itching and swelling (edema). Aplastic anemia or agranulocytosis may show up within hours to days. In an emergency call 999 or go to the nearest hospital emergency department.
How should I store Tapazol?
Keep Methimazole in a cool, dry place below 30°C, away from light and out of children's reach.
Can I take other medicines with Tapazol?
Some medicines can interact with Methimazole, for example: Theophylline, Warfarin Sodium. Tell your doctor or pharmacist about every medicine you take.
Is there a cheaper medicine with the same ingredient?
Tapazol is already among the lowest-priced brands of Methimazole at this strength.
Do I need a prescription for Tapazol?
Tapazol is a prescription (Rx) medicine. Take it as your doctor advises.