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Methimazole
- indication:For the treatment of hyperthyroidism, goiter, Graves disease and psoriasis.
- pharmacologypharmacology:
- mechanism: Methimazole binds to thyroid peroxidase and thereby inhibits the conversion of iodide to iodine. Thyroid peroxidase normally converts iodide to iodine (via hydrogen peroxide as a cofactor) and also catalyzes the incorporation of the resulting iodide molecule onto both the 3 and/or 5 positions of the phenol rings of tyrosines found in thyroglobulin. Thyroglobulin is degraded to produce thyroxine (T4) and tri-iodothyronine (T3), which are the main hormones produced by the thyroid gland. So methimazole effectively inhibits the production of new thyroid hormones.
- toxicity: Oral LD<sub>50</sub> in rats is 2250 mg/kg. Symptoms of overdose include nausea, vomiting, epigastric distress, headache, fever, joint pain, pruritus, and edema. Aplastic anemia (pancy-topenia) or agranulocytosis may be manifested in hours to days. Less frequent events are hepatitis, nephrotic syndrome, exfoliative dermatitis, neuropathies, and CNS stimulation or depression.
- absorprion: Rapid with an oral bioavailability of 93%.
- halflife: 5-6 hours
- roouteelimination: Methimazole is excreted in the urine.
- volumedistribution:
- clearance: