Thiamazole - Methimazole

In a study using a competitive radiobinding assay, as many as 43% of patients with rheumatoid arthritis using penicillamine had autoantibodies against insulin (132). These antibodies did not appear to affect pancreatic beta-cells, as the response to intravenous glucose was normal and there were no episodes of hypoglycemia. Other sulfhydryl compounds that have occasionally been reported to cause autoimmune hypoglycemia are tio-pronin, pyritinol, and thiamazole (methimazole) (133). 

The patient usually starts with 20 mg of thiamazole (methimazole), unless iodine-induced or severe hyperthyroidism exists, necessitating a higher starting dose (Table 81.2). Doses of thionamide drugs are lower in the case of iodine deficiency because the drugs act as competitive inhibitors of thyroid peroxidase and are antagonized by iodine. The doses have to be adjusted individually and, after restoration of euthyroidism, should be reduced to a lower maintenance dose (2.5—10 mg of thiamazole). 

The serum theophylline level of an asthmatic patient was found to have doubled, from 15.2 to 30.9 mg/L, accompanied by toxicity, 3 months after treatment for hyperthyroidism with radioactive iodine ( I). At this point the patient was hypothyroid, and after treatment with levothyroxine was started, his serum theophylline returned to approximately the same level as before radioactive iodine treatment (13.9 mg/L). Another patient with Graves disease treated with a combination of thiamazole (methimazole)... 

A solution containing 10-60 ug thiamazole was buffered at pH 5.6, treated with NaN3 and then with 0.02 M iodine solution, left 10 minutes and titrated for unchanged iodine with 0.02 M Na3As03. The method was useful in determining methimazole in compound drugs provided they... 

In this method the reaction of diphenylpicrylhydra-sine with methimazole (thiamazole) was sufficiently rapid for its use in a spectrophotometric assay. 

Methimazole also directly disrupts thyroxine and triiodothyronin sysnthesis in the thyroid gland, and it is used for the same indications as propylthiouracil and methylthiouracil to treat hyperfunctioning thyroid glands in patients with Basedow s disease. Synonyms of this drug are merazolil, thiamazole, metothyrin, timidazol, and others. 

The available agents with antithyroid activity are the thioamides propylthiouracil, carbimazole and methimazole also known as thiamazole. Their thio-carbamide group is indispensable for antithyroid activity. The mechanism of action is complex. The most important action is the prevention of hormone synthesis by an inhibition of the thyroid peroxidase-catalyzed reactions involved in iodine organification. These agents also block the coupling of the iodoty-rosines. 

Additional cases of aplasia cutis congenita in thiona-mide-exposed infants associated with other congenital abnormalities, such as choanal atresia, esophageal atresia, imperforate anus, and cardiovascular defects, were also reviewed. This pattern of abnormalities has previously led to the term methimazole [thiamazole] embryopathy (95). 

Common Name Mercazolyl(um) Methimazole Methymazole Thiamazole Tiamazol... 

Some changes in nomenclature follow from WHO s Intematioml Nonproprietaiy Names for Pharmaceutical Substances (1982). Adrenaline, oestrone, and sulphanila-mide have become epinephrine, estrone, and sulfanilamide, respectively. American readers will note the following changes in that list (the internationally agreed name is in parentheses) acetaminophen (paracetamol), albuterol (salbutamol), chlorpheniramine (chlorphenamine), dibucaine (cinchocaine), isoproterenol (isoprenaline), mechlorethamine (chlormethine), melphalan (sarcolysin), meperidine (pethidine), metaproterenol (orciprenaline), pyril-amine (mepyramine), methimazole (thiamazole) and rifampin (rifampicin). 

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