THYROZOL TABLET 5 mg

MERCK PTE. LTD.

MERCK PTE. LTD.

Therapeutic

Prescription Only

TABLET, FILM COATED

**Posology and method of administration** General dosage recommendations _Dosage in adults_ Inhibition of thyroid hormone production can usually be achieved with daily doses of 25 to 40 mg thiamazole. For mild cases, an initial dose of 20 mg thiamazole daily may be considered. In severe cases of hyperthyroidism an initial dose of 40 mg thiamazole may be required. The dose is individually adjusted depending on the metabolic condition of the patient, as indicated by the development of the thyroid hormone status. For maintenance therapy, one of the following treatment options is recommended: 1. Daily maintenance dose of 5–20 mg thiamazole in combination with levothyroxine, in order to avoid hypothyroidism. 2. Monotherapy with daily doses of 2.5 and 10 mg thiamazole. Iodine-induced hyperthyroidism may possibly require higher dosages. _Dosage in children:_ The initial dose depending on the severity of the disease is 0.3 – 0.5 mg/kg body weight per day. After normalization of the thyroid function, the dose is gradually reduced to a lower maintenance dose of 0.2 – 0.3 mg/kg body weight per day, which depends on the metabolic condition of the patient. Additional treatment with thyroid hormone may be required to avoid hypothyroidism. **Conservative treatment of hyperthyroidism:** In conservative treatment of hyperthyroidism, therapy is usually continued over a period of 6 months to 2 years (1 year on average). Statistically, the probability of remission increases with the duration of therapy. In cases where remission of the disease cannot be achieved and definite therapeutic measures do not apply or are rejected, thiamazole may be used as long-term anti-thyroid therapy in as low a dosage as possible without addition or in combination with a low dose of levothyroxine. Patients with large goiters and constriction of the trachea should, if at all, only undergo short-term treatment with thiamazole since long-term administration can result in goitre growth. It may be necessary to monitor therapy particularly thoroughly (TSH level, tracheal lumen). The treatment is preferably combined with thyroid hormones. **Pre-operative therapy** Temporary pre-treatment, (for about 3 to 4 weeks or longer, if individually needed), may serve to achieve a euthyroid metabolic condition thus reducing surgery-related risks. Surgery should be performed as soon as the patient is euthyroid, as otherwise, supplementary thyroid hormones must be administered. Treatment may be terminated the day before surgery. The thiamazole-induced increased brittleness and bleeding tendency of thyroid tissues may be compensated by additional pre-operative administration of high-dose iodine during the ten days preceding surgery (Plummer’s iodine therapy). **Treatment prior to radioiodine therapy:** Achievement of a euthyroid metabolism, before initiation of radioiodine therapy is important particularly in severe hyperthyroidism, as post-therapeutic thyrotoxic crisis has occurred in individual cases after such therapy without pre-treatment. Note: Thiourea derivatives may reduce the radiosensitivity of the thyroid tissue. In scheduled radioiodine therapy of autonomous adenoma, activation of paranodular tissue by means of pre-treatment must be prevented. **Intermittent antithyroid therapy after treatment with radioiodine** The duration and dose of treatment must be defined individually depending on the severity of the clinical picture and the estimated period until radioiodine therapy starts to be effective (approximately 4–6 months). **Long-term antithyroid therapy in cases where remission of the disease cannot be achieved and definite therapeutic measures do not apply or are rejected:** Thiamazole in as low a dose as possible (2.5–10 mg per day) without additional or together with a small amount of thyroid hormone. **Prophylactic treatment in patients with a history of hyperthyroidism and autonomous adenomas in whom iodine exposure is indispensable** In general, daily doses of 10 to 20mg thiamazole and/or 1g perchlorate are administered for approx. 10 days (e.g. for renally excreted contrast media). The duration of treatment depends on the period of time for which the iodine-containing substance is retained in the body. Special populations In patients with hepatic impairment, the plasma clearance of thiamazole is reduced. Therefore, the dose should be kept as low as possible and patients should be closely monitored. Due to the lack of pharmacokinetic data for thiamazole in patients with renal impairment, careful individual dose adjustment under close monitoring is recommended. The dose should be as low as possible. Although no accumulation is expected in elderly patients, careful individual dose adjustment with close monitoring is recommended. Administration The tablets are to be swallowed whole with sufficient liquid after meals. During high-dose initial therapy of hyperthyroidism, the above stated single doses can be subdivided and taken at regular intervals over the day. The maintenance dose can be taken all at once in the morning during or after breakfast.