Carbimazole


Concise Prescribing Info
Indications/Uses
Listed in Dosage.
Dosage/Direction for Use
Adult : PO Hyperthyroidism; Adjunct to radio-iodine therapy; Preparation for thyroidectomy Initial: 15-60 mg/day in 2-3 divided doses, reduced gradually once euthyroidism is achieved. Maintenance: 5-15 mg/day as a single dose. Blocking replacement regimen: Initial: 20-60 mg in 2-3 divided doses in combination with levothyroxine. Treatment duration: 6-18 months.
Dosage Details
Oral
Adjunct to radio-iodine therapy, Hyperthyroidism, Preparation for thyroidectomy
Adult: Initially, 15-60 mg daily in 2-3 divided doses, reduced gradually once euthyroidism is achieved. Maintenance: 5-15 mg daily (may be taken as a single dose). Blocking replacement regimen: Initially, 20-60 mg in 2-3 divided doses in combination with levothyroxine. Treatment duration: 6-18 months.
Child: 3-17 years Initially, 15 mg daily adjusted according to response.
Hepatic Impairment
Severe: Contraindicated.
Administration
May be taken with or without food. Take consistently w/ or w/o meals.
Contraindications
Serious, pre-existing haematological conditions. History of acute pancreatitis. Severe hepatic impairment.
Special Precautions
Patient with intrathoracic goitre, any degree of tracheal obstruction. Stop carbimazole temporarily at the time of radio-iodine administration. Mild to moderate hepatic impairment. Children. Pregnancy and lactation.
Adverse Reactions
Significant: Bone marrow depression (e.g. neutropenia, eosinophilia, leucopenia), acute pancreatitis.
Blood and lymphatic system disorders: Rarely, pancytopenia, aplastic anaemia, haemolytic anaemia, thrombocytopenia.
Endocrine disorders: Insulin autoimmune syndrome.
Gastrointestinal disorders: Nausea, mild gastrointestinal disturbance, loss of sense of taste, acute salivary gland swelling.
General disorders and administration site conditions: Fever, malaise.
Hepatobiliary disorders: Abnormal LFT, jaundice, hepatitis, cholestatic hepatitis, cholestatic jaundice.
Immune system disorders: Angioedema, hypersensitivity reactions (e.g. cutaneous vasculitis, liver, lung and renal effects).
Musculoskeletal and connective tissue disorders: Arthralgia.
Nervous system disorders: Headache, neuritis, polyneuropathy.
Skin and subcutaneous tissue disorders: Rash, pruritus, urticaria, hair loss. Rarely, Stevens-Johnson syndrome.
Vascular disorders: Bleeding.
Potentially Fatal: Agranulocytosis.
MonitoringParameters
Perform confirmatory test for hyperthyroidism prior to initiation of therapy. Perform regular FBC checks in patients who may be confused or have poor memory. Monitor for possible symptoms of agranulocytosis (e.g. sore throat, bruising or bleeding, mouth ulcers, fever, malaise).
Drug Interactions
May have cross-sensitivity with propylthiouracil (PTU) or thiamazole. May enhance the effect of anticoagulants. May increase the serum levels of theophylline which may result in toxicity. May increase the clearance of prednisolone. May reduce the clearance of erythromycin. Hyperparathyroid patients who become euthyroid may have increased serum concentration of digitalis and increased clearance of β-blockers.
Action
Description: Carbimazole is completely metabolised to thiamazole which is responsible for its antithyroid action. It blocks the production of thyroid hormones through inhibition of the organification of iodide and the coupling of iodothyronine residues.
Pharmacokinetics:
Absorption: Rapidly absorbed from the gastrointestinal tract. Time to peak plasma concentration: Approx 1-2 hours (as thiamazole).
Distribution: Concentrated in the thyroid gland (as thiamazole). Crosses the placenta and enters breast milk (as thiamazole). Volume of distribution: 0.5 L/kg. Plasma protein binding: Moderately bound (as thiamazole).
Metabolism: Rapidly and completely metabolised to thiamazole.
Excretion: Via urine (approx >90%, as thiamazole or its metabolites). Elimination half-life: Approx 5.3-5.4 hours.
Chemical Structure

Chemical Structure Image
Carbimazole

Source: National Center for Biotechnology Information. PubChem Database. Carbimazole, CID=31072, https://pubchem.ncbi.nlm.nih.gov/compound/Carbimazole (accessed on Jan. 21, 2020)

Storage
Store below 25°C. Protect from moisture.
MIMS Class
ATC Classification
H03BB01 - carbimazole ; Belongs to the class of sulfur-containing imidazole derivative agents. Used in the management of thyroid diseases.
References
Anon. Carbimazole. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 20/08/2019.

Buckingham R (ed). Carbimazole. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 20/08/2019.

Joint Formulary Committee. Carbimazole. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 20/08/2019.

NeoMercazole Tablet (A. Menarini Singapore Pte. Ltd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my/. Accessed 20/08/2019.

Disclaimer: This information is independently developed by MIMS based on Carbimazole 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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