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Mercazolil® [Tiamazol]

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Clinical Pharmacology

Antithyroid agent. It blocks peroxidase enzyme involved in thyroid hormone iodization of the thyroid gland, which leads to disruption of the synthesis of thyroxin and triiodothyronine.


  • Diffuse toxic goiter;
  • thyrotoxic crisis;
  • mixed toxic goiter (as part of combination therapy with thyroid hormone preparations);
  • as part of combination therapy with radioactive iodine.


Excipients: potato starch, calcium stearate, sucrose, talc.

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Mercazolil® [Tiamazol]

Dosage and Administration

Inside after eating, without chewing, with enough liquid.

The daily dose is prescribed in one step or divided into 2-3 single doses. At the beginning of treatment, single doses are applied during the day at a strictly defined time.

Maintenance dose should be taken in 1 reception after breakfast.

Thyrotoxicosis: depending on the severity of the disease, 20–40 mg / day of Tyrozol for 3–6 weeks. After normalization of thyroid function (usually after 3–8 weeks), they switch to a maintenance dose of 5–20 mg / day. From now on, additional administration of levothyroxine is recommended.

In preparation for the surgical treatment of thyrotoxicosis: prescribed 20-40 mg / day to achieve a euthyroid state. From now on, additional administration of levothyroxine is recommended.

In order to reduce the time required to prepare for the operation, beta-blockers and iodine preparations are additionally prescribed.

In preparation for treatment with radioactive iodine: 20–40 mg / day to achieve a euthyroid state.

Therapy in the latent period of radioactive iodine: depending on the severity of the disease, 5–20 mg before the onset of radioactive iodine (4–6 months).

Prolonged thyreostatic maintenance therapy: 1.25; 2.5; 10 mg / day with an additional small doses of levothyroxine. In the treatment of thyrotoxicosis, the duration of therapy ranges from 1.5 to 2 years.

Prevention of thyrotoxicosis in the appointment of iodine preparations (including cases of use of iodine-containing radiopaque agents) in the presence of latent thyrotoxicosis, autonomous adenomas or thyrotoxicosis in history: 10–20 mg / day of Tyrozol and 1 g of potassium perchlorate per day for 8–10 days before taking iodine-containing products.

Dosage in children. Not recommended for use in children from 0 to 3 years. Children from 3 to 17 years old are prescribed Tyrozol at the initial dose of 0.3–0.5 mg / kg body weight, which is divided into 2-3 equal doses daily; The maximum recommended dose for children weighing more than 80 kg is 40 mg / day.

Maintenance dose is 0.2–0.3 mg / kg, if necessary, additional levothyroxine is prescribed.

Dosage in pregnant women. Pregnant women are prescribed in the lowest possible doses: single dose - 2.5 mg, daily dose - 10 mg.

When liver failure prescribe a minimally effective dose of the drug under close medical supervision.

In preparation for the operation of patients with thyrotoxicosis, treatment with the drug is carried out until the euthyroid state is reached within 3-4 weeks before the scheduled day of the operation (in some cases longer), and ends a day before it.

Adverse reactions

From the circulatory and lymphatic systems: infrequently - agranulocytosis (its symptoms (see “Special Instructions”) can appear even weeks and months after the start of treatment and lead to the need to discontinue the drug); very rarely - generalized lymphadenopathy, thrombocytopenia, pancytopenia.

On the part of the endocrine system: very rarely - insulin autoimmune syndrome with hypoglycemia.

From the nervous system: rarely - reversible change in taste, dizziness; very rarely - neuritis, polyneuropathy.

From the digestive tract: very rarely - an increase in the salivary glands, vomiting.

Liver and biliary tract: very rarely, cholestatic jaundice and toxic hepatitis.

Skin and Subcutaneous Tissues: very often - allergic skin reactions (itching, redness, rash); very rarely - generalized skin rash, alopecia, lupus-like syndrome.

From the musculoskeletal and connective tissues: often - slowly progressive arthralgia without clinical signs of arthritis.

General complications and reactions at the injection site: rarely - fever, weakness, weight gain.

Carefully: should be used in patients with goiter very large sizes, narrowing of the trachea (only short-term treatment during the preparation for surgery), with liver failure.

Drug interactions

In the appointment of thiamazol after the use of iodine-containing radiopaque agents in a high dose, it is possible to weaken the action of thiamazole.

Lack of iodine increases the action of thiamazole.

In patients taking thiamazol for the treatment of thyrotoxicosis, after reaching a euthyroid state, i.e. normalization of serum thyroid hormones, it may be necessary to reduce the received doses of cardiac glycosides (digoxin and digitoxin), aminophylline, as well as increase the doses of warfarin and other anticoagulants derived from coumarin and indandion (pharmacodynamic interaction).

Lithium preparations, beta-blockers, reserpine, amiodarone increase the effect of thiamazole (dose adjustment is required).

With simultaneous use of sulfonamides, metamizole sodium and myelotoxic drugs increases the risk of leukopenia.

Leucogen and folic acid with simultaneous use with tiamazol reduce the risk of leukopenia.

Gentamicin enhances the antithyroid effect of thiamazole.

There is no data on the effect of other drugs on the pharmacokinetics and pharmacodynamics of the drug. However, it should be borne in mind that with thyrotoxicosis, metabolism and elimination of substances is accelerated. Therefore, in some cases it is necessary to adjust the dose of other drugs.

Pregnancy and Lactation

Lack of treatment for hyperthyroidism during pregnancy can lead to serious complications such as premature birth, fetal malformations. Tiamazole penetrates the placental barrier and in the fetal blood can reach the same concentration as that of the mother. Due to the fact that the effect of thiamazol on the fetus cannot be completely excluded, during pregnancy the drug should be administered after a full assessment of the benefits and risks of its use in the minimum effective dose without additional administration of levothyroxine.

Doses of thiamazole, much higher than the recommended, can cause goiter and hypothyroidism in the fetus, as well as reduced birth weight.
During lactation, the treatment of thyrotoxicosis with Tyrozol can be continued if necessary. Since tiamazol penetrates into breast milk and can reach a concentration in it that corresponds to its level in the mother’s blood, hypothyroidism may develop in the newborn. Therefore, if it is necessary to continue the treatment of thyrotoxicosis during breastfeeding, tyrosol should be taken in low doses (up to 10 mg / day) without additional administration of levothyroxine.

Special instructions

Patients with a significant enlargement of the thyroid gland, which narrows the lumen of the trachea, Tyrozol is administered briefly in combination with levothyroxine sodium, because With prolonged use, an increase in goiter and even more tracheal compression is possible. It is necessary to conduct careful monitoring of the patient (monitoring the level of TSH, tracheal lumen). During the period of drug treatment requires regular monitoring of the pattern of peripheral blood.

Thiamazole and thiourea derivatives can reduce the sensitivity of thyroid tissue to radiation therapy. If during treatment with a drug suddenly there is pain in the throat, difficulty swallowing, fever, signs of stomatitis or furunculosis (possible symptoms of agranulocytosis), you should stop taking the drug and consult a doctor immediately.

When subcutaneous hemorrhages or bleeding of unclear genesis, generalized skin rash and itching, persistent nausea or vomiting, jaundice, severe epigastric pain and severe weakness, the drug should be removed during treatment. In case of early termination of treatment, a relapse of the disease is possible.The appearance or worsening of the course of endocrine ophthalmopathy is not a side effect of treatment with the drug Tyrozol, carried out properly. In rare cases, after the end of treatment, late hypothyroidism may occur, which is not a side effect of the drug, but is associated with inflammatory and destructive processes in the thyroid tissue, occurring within the framework of the underlying disease.

Impact on the ability to drive vehicles and mechanisms. Tiamazol does not affect the ability to drive vehicles and mechanisms.


With prolonged high doses of the drug may develop subclinical and clinical hypothyroidism, as well as an increase in the size of the thyroid gland due to increased levels of TSH. This can be avoided by lowering the dose of the drug to achieve a state of euthyroidism or, if necessary, by the additional prescription of levothyroxine sodium. As a rule, after discontinuation of the drug Tyrosol, a spontaneous restoration of thyroid function is observed. Taking very high doses of thiamazole (about 120 mg per day) can lead to the development of myelotoxic effects. Such doses of the drug should be used only for special indications (severe forms of the disease, thyrotoxic crisis).

Treatment: drug withdrawal, gastric lavage, symptomatic therapy, if necessary - transfer to an antithyroid drug of another group.

  • Brand name: Mercazolil
  • Active ingredient: Tiamazol

Studies and clinical trials of Tiamazol (Click to expand)

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