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Methimazole

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Overview

What is Methimazole?

Methimazole (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.

Each tablet contains 5 or 10 mg (43.8 or 87.6 µmol) 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 CHNS. The structural formula is as follows:



What does Methimazole look like?



What are the available doses of Methimazole?

Sorry No records found.

What should I talk to my health care provider before I take Methimazole?

Sorry No records found

How should I use Methimazole?

Methimazole is indicated in the medical treatment of hyperthyroidism. Long-term therapy may lead to remission of the disease.

Methimazole may be used to ameliorate hyperthyroidism in preparation for subtotal thyroidectomy or radioactive iodine therapy.

Methimazole is also used when thyroidectomy is contraindicated or not advisable.

Methimazole is administered orally. It is usually given in 3 equal doses at approximately 8-hour intervals.

Adults

Pediatric


What interacts with Methimazole?

Methimazole is contraindicated in the presence of hypersensitivity to the drug and in nursing mothers because the drug is excreted in milk.



What are the warnings of Methimazole?

After the diagnosis of pseudomembranous colitis has been established, appropriate therapeutic measures should be initiated. Mild cases of pseudomembranous colitis usually respond to drug discontinuation alone. In moderate to severe cases, consideration should be given to management with fluids and electrolytes, protein supplementation, and treatment with an antibacterial drug clinically effective against colitis.

Agranulocytosis is potentially a serious side effect. Patients should be instructed to report to their physicians any symptoms 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, aplastic anemia (pancytopenia), hepatitis, or exfoliative dermatitis. The patient's bone marrow function should be monitored.

Due to the similar hepatic toxicity profiles of methimazole and propylthiouracil, attention is drawn to the severe hepatic reactions which have occurred with both drugs. There have been rare reports of fulminant hepatitis, hepatic necrosis, encephalopathy, and death.

Symptoms suggestive of hepatic dysfunction (anorexia, pruritus, right upper quadrant pain, etc.) should prompt evaluation of liver function. 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.

Methimazole can cause fetal harm when administered to a pregnant woman. Methimazole readily crosses the placental membranes and can induce goiter and even cretinism in the developing fetus. In addition, rare instances of congenital defects: aplasia cutis, as manifested by scalp defects; esophageal atresia with tracheoesophageal fistula; and choanal atresia with absent/hypoplastic nipples, have occurred in infants born to mothers who received methimazole during 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. Since the above congenital defects have been reported in offspring of patients treated with methimazole, it may be appropriate to use other agents in pregnant women requiring treatment for hyperthyroidism.

Postpartum patients receiving methimazole should not nurse their babies.


What are the precautions of Methimazole?

General

Patients who receive methimazole should be under close surveillance and should be cautioned to report immediately any evidence of illness, particularly sore throat, skin eruptions, fever, headache, or general malaise. In such cases, white-blood cell and differential counts should be made to determine whether agranulocytosis has developed. Particular care should be exercised with patients who are receiving additional drugs know to cause agranulocytosis.

Laboratory Tests

Because methimazole may cause hypoprothrombinemia and bleeding, prothrombin time should be monitored during therapy with the drug, especially before surgical procedures (see under PRECAUTIONS).

Periodic monitoring of thyroid function is warranted, and the finding of an elevated TSH warrants a decrease in the dosage of methimazole.

Drug Interactions

Anticoagulants (oral)

ß-adrenergic blocking agents

Digitalis glycosides

Theophylline

Carcinogenesis, Mutagenesis, Impairment of Fertility

In a 2 year study, rats were given methimazole at doses of 0.5, 3, and 18 mg/kg/day. These doses were 0.3, 2, and 12 times the 15 mg/day maximum human maintenance dose (when calculated on the basis of surface area). Thyroid hyperplasia, adenoma, and carcinoma developed in rats at the two higher doses. The clinical significance of these findings is unclear.

Pregnancy

Category D

Nursing Mothers

The drug appears in human breast milk and its use is contraindicated in nursing mothers (see ).

Pediatric Use

(See ).


What are the side effects of Methimazole?

Major adverse reactions (which occur with much less frequency than the minor adverse reactions) include inhibition of myelopoiesis (agranulocytosis, granulocytopenia, and thrombocytopenia), aplastic anemia, drug fever, a lupuslike 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.

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.

It should be noted that about 10% of patients with untreated hyperthyroidism have leukopenia (white-blood cell count of less than 4,000/mm ), often with relative granulopenia.


What should I look out for while using Methimazole?

Methimazole is contraindicated in the presence of hypersensitivity to the drug and in nursing mothers because the drug is excreted in milk.

Agranulocytosis is potentially a serious side effect. Patients should be instructed to report to their physicians any symptoms 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, aplastic anemia (pancytopenia), hepatitis, or exfoliative dermatitis. The patient's bone marrow function should be monitored.

Due to the similar hepatic toxicity profiles of methimazole and propylthiouracil, attention is drawn to the severe hepatic reactions which have occurred with both drugs. There have been rare reports of fulminant hepatitis, hepatic necrosis, encephalopathy, and death.

Symptoms suggestive of hepatic dysfunction (anorexia, pruritus, right upper quadrant pain, etc.) should prompt evaluation of liver function. 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.

Methimazole can cause fetal harm when administered to a pregnant woman. Methimazole readily crosses the placental membranes and can induce goiter and even cretinism in the developing fetus. In addition, rare instances of congenital defects: aplasia cutis, as manifested by scalp defects; esophageal atresia with tracheoesophageal fistula; and choanal atresia with absent/hypoplastic nipples, have occurred in infants born to mothers who received methimazole during 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. Since the above congenital defects have been reported in offspring of patients treated with methimazole, it may be appropriate to use other agents in pregnant women requiring treatment for hyperthyroidism.

Postpartum patients receiving methimazole should not nurse their babies.


What might happen if I take too much Methimazole?

Signs and Symptoms

Treatment

Protect the patient's airway and support ventilation and perfusion. Meticulously monitor and maintain, within acceptable limits, the patient's vital signs, blood gases, serum electrolytes, etc. The patient's bone marrow function should be monitored. Absorption of drugs from the gastrointestinal tract may be decreased by giving activated charcoal, which, in many cases, is more effective than emesis or lavage; consider charcoal instead of or in addition to gastric emptying. Repeated doses of charcoal over time may hasten elimination of some drugs that have been absorbed. Safeguard the patient's airway when employing gastric emptying or charcoal.

Forced diuresis, peritoneal dialysis, hemodialysis, or charcoal hemoperfusion have not been established as beneficial for an overdose of methimazole.


How should I store and handle Methimazole?

Store at controlled room temperature 20° to 25°C (68° to 77°F)Rx onlyManufactured by:Yung Shin Pharmaceutical Industrial Co., Ltd.Tachia, TaichungTaiwan, ROCRevision: April 2007Store at controlled room temperature 20° to 25°C (68° to 77°F)Rx onlyManufactured by:Yung Shin Pharmaceutical Industrial Co., Ltd.Tachia, TaichungTaiwan, ROCRevision: April 2007Store at controlled room temperature 20° to 25°C (68° to 77°F)Rx onlyManufactured by:Yung Shin Pharmaceutical Industrial Co., Ltd.Tachia, TaichungTaiwan, ROCRevision: April 2007Store at controlled room temperature 20° to 25°C (68° to 77°F)Rx onlyManufactured by:Yung Shin Pharmaceutical Industrial Co., Ltd.Tachia, TaichungTaiwan, ROCRevision: April 2007Store at controlled room temperature 20° to 25°C (68° to 77°F)Rx onlyManufactured by:Yung Shin Pharmaceutical Industrial Co., Ltd.Tachia, TaichungTaiwan, ROCRevision: April 2007Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01Methimazole Tablets, USP 5 mg white, round, flat-faced, bevelled-edged tablets with “VM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1945-01Methimazole Tablets, USP 10 mg white, round, flat-faced, bevelled-edged tablets with “XM” on one side and scored on the other.They are available in:Bottles of 100 NDC 0677-1946-01Store at controlled room temperature, 20°- 25°C (68°- 77°F).Dispense in tight, light-resistant container.DISTRIBUTED BY:UNITED RESEARCH LABORATORIES, INC.Philadelphia, PA 191240677-1946-01


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Clinical Information

Chemical Structure

No Image found
Clinical Pharmacology

Methimazole inhibits the synthesis of thyroid hormones and thus is effective in the treatment of hyperthyroidism. The drug does not inactivate existing thyroxine and triiodothyronine that are stored in the thyroid or circulating in the blood nor does it interfere with the effectiveness of thyroid hormones given by mouth or by injection.

The actions and use of methimazole are similar to those of propylthiouracil. On a weight basis, the drug is at least 10 times as potent as propylthiouracil, but methimazole may be less consistent in action.

Methimazole is readily absorbed from the gastrointestinal tract. It is metabolized rapidly and requires frequent administration.

Methimazole is excreted in the urine.

In laboratory animals, various regimens that continuously suppress thyroid function and thereby increase TSH secretion result in thyroid tissue hypertrophy. Under such conditions, the appearance of thyroid and pituitary neoplasms has also been reported. Regimens that have been studied in this regard include antithyroid agents as well as dietary iodine deficiency, subtotal thyroidectomy, implantation of autonomous thyrotropic hormone-secreting pituitary tumors, and administration of chemical goitrogens.

Non-Clinical Toxicology
Methimazole is contraindicated in the presence of hypersensitivity to the drug and in nursing mothers because the drug is excreted in milk.

Agranulocytosis is potentially a serious side effect. Patients should be instructed to report to their physicians any symptoms 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, aplastic anemia (pancytopenia), hepatitis, or exfoliative dermatitis. The patient's bone marrow function should be monitored.

Due to the similar hepatic toxicity profiles of methimazole and propylthiouracil, attention is drawn to the severe hepatic reactions which have occurred with both drugs. There have been rare reports of fulminant hepatitis, hepatic necrosis, encephalopathy, and death.

Symptoms suggestive of hepatic dysfunction (anorexia, pruritus, right upper quadrant pain, etc.) should prompt evaluation of liver function. 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.

Methimazole can cause fetal harm when administered to a pregnant woman. Methimazole readily crosses the placental membranes and can induce goiter and even cretinism in the developing fetus. In addition, rare instances of congenital defects: aplasia cutis, as manifested by scalp defects; esophageal atresia with tracheoesophageal fistula; and choanal atresia with absent/hypoplastic nipples, have occurred in infants born to mothers who received methimazole during 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. Since the above congenital defects have been reported in offspring of patients treated with methimazole, it may be appropriate to use other agents in pregnant women requiring treatment for hyperthyroidism.

Postpartum patients receiving methimazole should not nurse their babies.

Anticoagulants (oral)

ß-adrenergic blocking agents

Digitalis glycosides

Theophylline

Patients who receive methimazole should be under close surveillance and should be cautioned to report immediately any evidence of illness, particularly sore throat, skin eruptions, fever, headache, or general malaise. In such cases, white-blood cell and differential counts should be made to determine whether agranulocytosis has developed. Particular care should be exercised with patients who are receiving additional drugs know to cause agranulocytosis.

Major adverse reactions (which occur with much less frequency than the minor adverse reactions) include inhibition of myelopoiesis (agranulocytosis, granulocytopenia, and thrombocytopenia), aplastic anemia, drug fever, a lupuslike 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.

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.

It should be noted that about 10% of patients with untreated hyperthyroidism have leukopenia (white-blood cell count of less than 4,000/mm ), often with relative granulopenia.

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Reference

This information is obtained from the National Institute of Health's Standard Packaging Label drug database.
"https://dailymed.nlm.nih.gov/dailymed/"

While we update our database periodically, we cannot guarantee it is always updated to the latest version.

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Professional

Clonazepam Description Each single-scored tablet, for oral administration, contains 0.5 mg, 1 mg, or 2 mg Clonazepam, USP, a benzodiazepine. Each tablet also contains corn starch, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and povidone. Clonazepam tablets USP 0.5 mg contain Yellow D&C No. 10 Aluminum Lake. Clonazepam tablets USP 1 mg contain Yellow D&C No. 10 Aluminum Lake, as well as FD&C Blue No. 1 Aluminum Lake. Chemically, Clonazepam, USP is 5-(o-chlorophenyl)-1,3-dihydro-7-nitro-2H-1,4-benzodiazepin-2-one. It is a light yellow crystalline powder. It has the following structural formula: C15H10ClN3O3 M.W. 315.72
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Tips

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Interactions

Interactions

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