Thiamazole


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : PO Adjunct to radio-iodine therapy; Grave's disease; Hyperthyroidism; Preparation for thyroidectomy; Thyroid storm 15-60 mg/day in 1-3 divided doses. Maintenance: 5-15 mg/day. Usual duration: 1-2 yr. IV Thyroid storm 80-240 mg/day in 3-4 divided doses.
Dosage Details
Intravenous
Thyroid storm
Adult: 80-240 mg daily in 3-4 divided doses.

Oral
Adjunct to radio-iodine therapy, Graves' disease, Hyperthyroidism, Preparation for thyroidectomy, Thyroid storm
Adult: 15-60 mg daily (once daily or in 3 divided doses). Once patient is euthyroid, reduce to a maintenance dose of 5-15 mg daily. Alternatively, may continue at initial doses with supplemental levo-thyroxine. Usually continued for 1-2 yr.
Child: Initially, 400 mcg/kg in 3 divided doses daily. Maintenance: ½ the initial dose.
Administration
Should be taken with food.
Contraindications
Lactation.
Special Precautions
Pregnancy. Higher risk of agranulocytosis if doses >40 mg/day and in patients >40 yr. Monitor for signs and symptoms of agranulocytosis (e.g. sore throat, fever, chills, general malaise) especially during 1st few mth of therapy. Perform leukocyte and differential counts in patients who develop fever or sore throat or other signs or symptoms of illness.
Adverse Reactions
Allergic skin reactions, jaundice, nausea, vomiting, epigastric distress, loss of taste, arthralgia, myalgia, paraesthesia, headache, drowsiness, peripheral neuritis, vertigo, sialodenopathy, lymphadenopathy, drug fever, lupus-like syndrome, periarteritis, hypoprothrombinaemia, hypothyroidism (prolonged therapy).
Potentially Fatal: Blood dyscrasias especially agranulocytosis, hepatitis.
Overdosage
Nausea, vomiting, epigastric distress, headache, fever, pruritus, arthralgia, oedema, pancytopenia, agranulocytosis, exfoliative dermatitis, hepatitis, neuropathy, CNS stimulation or depression. Treatment is symptomatic and supportive. Empty stomach contents by inducing emesis or by gastric lavage. If the patient is comatose, having seizures or lacks the gag reflex, gastric lavage may be performed if an endotracheal tube with cuff inflated is in place to prevent aspiration of gastric contents. If bone marrow depression develops, use anti-infectives, corticosteroids and transfusions of fresh whole blood.
Drug Interactions
Avoid concurrent use with other drugs known to cause agranulocytosis (e.g. clozapine). Dosage of β-blockers, digoxin, warfarin and theophylline may require adjustments according to changes in thyroid status. Concurrent use may increase clearance of prednisolone; increased risk of QT prolongation with macrolides.
Action
Description: Thiamazole, also known as methimazole, acts by blocking the production of thyroid hormones. It inhibits the synthesis of thyroid hormones by blocking the oxidation of iodine and its ability to combine with tyrosine to form thyroxine and triiodothyronine (T3).
Onset: 12-18 hr.
Duration: 36-72 hr.
Pharmacokinetics:
Absorption: Rapidly absorbed from the GI tract. Peak plasma concentrations: 1 hr.
Distribution: Readily crosses the placenta; distributed into breastmilk. Elimination half-life: 5-13 hr.
Metabolism: Hepatic
Excretion: Excreted in urine.
Storage
Oral:
Store between 15-30°C.
MIMS Class
Disclaimer: This information is independently developed by MIMS based on Thiamazole from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2020 MIMS. All rights reserved. Powered by MIMS.com
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