Thyrozol

Thyrozol Mechanism of Action

thiamazole

Manufacturer:

PT. Merck Tbk
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Full Prescribing Info
Action
Pharmacology: Mode of Action: Thiamazole inhibits dose-dependently the incorporation of iodine into tyrosine and thereby the neosynthesis of thyroid hormones. This property permits symptomatic therapy of hyperthyroidism regardless of its cause. Whether thiamazole furthermore affects the "natural course" taken by the immunologically-induced type of hyperthyroidism (Graves' disease) ie, whether it suppresses the underlying immunopathogenetic process, can presently not be decided with certainty. The release of previously synthesised thyroid hormones from the thyroid is not affected. This explains why the length of the latency period until normalisation of the serum concentrations of thyroxine and triiodothyronine, and thus to clinical improvement, differs in individual cases. Hyperthyroidism is also unaffected by the release of hormones after destruction of the thyroid cells eg, after radioiodine therapy or in thyroiditis.
Nonclinical Safety Data: Preclinical safety studies are available to a limited extent only. Single-dose toxicity data show that the acute toxicity of thiamazole is low. In repeated-dose studies, bone marrow depression was seen at dose levels, which were considerably higher than the therapeutic dose levels.
Mutagenicity studies did not reveal any evidence of mutagenic or clastogenic effects. In a 2-year chronic toxicity study in rats, no relevant findings other than pharmacologically mediated effects on the thyroid were observed. In a 2-year chronic toxicity study in mice, a higher incidence of hepatomas, which did not reach the level of statistical significance, was seen when thiamazole was administered at a concentration of 500 mg/L in drinking water. The relevance of the latter finding is questionable and thiamazole is not classified as a carcinogenic substance according to the International Agency for Research of Cancer (IARC) or National Toxicology Program (NTP) criteria.
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