Thiamazole

Uses of Methimazole or Thiamazole

Methimazole is used to treat hyperthyroidism.

Mechanism of action

Inhibition of thyroid hormone synthesis (by inhibition of iodine oxidation in the thyroid gland)
Inhibition of the synthesis of thyroxine (T4) and triiodothyronine (T3)
No effect on T4 and T3 circulation

Pharmacokinetics of Methimazole

Absorption: Almost complete
Onset of action: anti-thyroid 18-12 hours
Effect length: 72-36 hours
Plasma peak: 2-1 hours
Protein binding: zero
Metabolism: Hepatic
Half-life: 6-4 hours
Urination

Side effects of Methimazole

Cardiovascular: edema, periarthritis
Central nervous system: drowsiness, drug fever, headache, neuritis, limb drowsiness, dizziness
Skin: Hair loss, itching, skin pigmentation, skin rash, urticaria
Endocrinology and metabolism: coma due to hypoglycemia, hypothyroidism, autoimmune insulin syndrome
Gastrointestinal: Lack of taste, enlarged salivary glands, epigastric pain (headache), nausea, vomiting
Hematology and oncology: agranulocytosis, aplastic anemia, granulocytopenia, prothrombin decline, leukopenia, lymphadenopathy, thrombocytopenia
Liver: Hepatitis, jaundice
Nervous, musculoskeletal: joint pain, lupus-like syndrome, muscle pain
Kidney: Nephritis

Drug Interactions Methimazole

Category X Interactions (Avoidance)

BCG (intravesical), cladribine, dipyrone, sodium iodide I131

Reducing the effects of drugs with Methimazole:

BCG (intravesical), prednisolone (systemic), sodium iodide I131, vitamin K antagonists

Reducing the effects of Methimazole by drugs:

No significant interference has been identified.

Enhance the effects of drugs with Methimazole:

Cardiac glycosides, clozapine, deferiprone, theophylline derivatives

Increased effects of methimazole by drugs:

Chloramphenicol (ophthalmic), cladribine, dipyrone, mesalamine, promazine

Warnings Methimazole

  1. The patient should be monitored for symptoms (such as fever, sore throat, skin lesions, and general malaise).
  2. Differential blood cell count (CBC with diff) is monitored at the beginning of treatment and in case of pharyngitis or febrile illness.
  3. Evaluate prothrombin time (PT) especially before surgery.
  4. Functional (bilirubin, alkaline phosphatase, alanine aminotransferase and aspartate aminotransferase) are monitored in the initial treatment and in case of symptoms of disease damage.
  5. Total FT4 and T3 levels should be assessed every 4-6 weeks during the dose adjustment period and then every 2-3 months after achieving the appropriate level of thyroid hormones. (In cases of prolonged use (for example, more than 18 months), the monitoring period may be extended to every 4-6 months.)
  6. TSH levels should be monitored periodically during treatment (TSH monitoring is not appropriate to assess the initial response to treatment, as levels may remain low for several months after starting treatment).
  7. If the TRAb test is negative in Graves’ disease, a thyroid function test should be performed every 2-3 months for the first 6 months after stopping the drug. In the second 6 months after cessation, be monitored every 4-6 months and then every 6-12 months.
  8. Monitor TRAb levels before stopping the drug. Increasing its level at the end of the treatment period reduces the likelihood of disease recurrence.
  9. It is necessary to check other medications used by the patient to adjust the dose or alternative therapy if needed.
  10. It is necessary to monitor the patient for signs of exacerbation of hyperthyroidism, rash, gastrointestinal upset, leukopenia, anemia and in the joints during the treatment period.
  11. Live vaccines (such as influenza, measles-mumps-rubella, mumps) are prohibited during treatment; Because there is a possibility of reducing the number of blood cells and increasing the risk of infection.
  12. In liver disease, blood cell disorders or bone marrow suppression should be prescribed with caution.
  13. Prolonged use of the drug may lead to hypothyroidism.

Methimazole drug recommendations

The drug should be taken at a specific time each day.

 

 

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