Carbimazole


Generic Medicine Info
Indications and Dosage
Oral
Adjunct to radio-iodine therapy, Hyperthyroidism, Preparation for thyroidectomy
Adult: Initially, 15-60 mg daily in 2-3 divided doses, titrate dose against thyroid function until euthyroidism is achieved. Maintenance: 5-15 mg daily (may be given as a single dose), adjust dose as needed to maintain euthyroid state. Blocking-replacement regimen: Initially, 20-60 mg daily 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 (after carbimazole or thiamazole administration). Severe hepatic impairment.
Special Precautions
Patient with intrathoracic goitre. Temporarily stop carbimazole therapy at the time of radio-iodine administration. Renal and mild to moderate hepatic impairment. Children and elderly. Pregnancy and lactation.
Adverse Reactions
Significant: Hypoprothrombinaemia, bleeding; haematologic effects or bone marrow depression (e.g. neutropenia, eosinophilia, leucopenia); acute pancreatitis. Rarely, severe dermatologic reactions (e.g. cutaneous vasculitis, erythema nodosum, dermatomyositis); hepatic reactions (e.g. cholestatic hepatitis, jaundice).
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.
Immune system disorders: Angioedema, multisystem hypersensitivity reactions.
Investigations: Abnormal LFT.
Musculoskeletal and connective tissue disorders: Arthralgia, myopathy.
Nervous system disorders: Headache, neuritis, polyneuropathy.
Skin and subcutaneous tissue disorders: Rash, pruritus, urticaria, hair loss. Rarely, Stevens-Johnson syndrome.
Potentially Fatal: Agranulocytosis.
Monitoring Parameters
Perform confirmatory test for hyperthyroidism prior to initiation of therapy. Monitor CBC with differential, LFT at baseline and when clinically indicated; prothrombin time periodically and prior to surgery; creatine kinase as clinically indicated. Monitor thyroid function 2-6 weeks after initiation of therapy, repeat in 4-6 weeks if dose is adjusted, then every 2-3 months once euthyroid is achieved. Monitor TSH periodically. Assess for signs and symptoms of illness (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 to toxicity. May increase the clearance of prednisolone. May reduce the clearance of erythromycin.
Action
Description: Carbimazole, a prodrug, is metabolised into thiamazole (also known as methimazole) which is responsible for its antithyroid action. It inhibits the organification of iodide and coupling of iodothyronine residues leading to the suppression of thyroid hormone synthesis.
Onset: 12-18 hours (thiamazole).
Duration: 36-72 hours (thiamazole).
Pharmacokinetics:
Absorption: Rapidly absorbed from the gastrointestinal tract. Time to peak plasma concentration: Approx 1-2 hours (thiamazole).
Distribution: Concentrated in the thyroid gland (thiamazole). Crosses the placenta and enters breast milk. Volume of distribution: 0.5 L/kg (thiamazole). Plasma protein binding: Moderately bound (thiamazole).
Metabolism: Rapidly and completely metabolised in the liver into thiamazole (active metabolite); undergoes enterohepatic recirculation.
Excretion: Via urine (approx 90%, as thiamazole or its metabolite); faeces (10%). Elimination half-life: 5.3-5.4 hours (carbimazole); approx 3-6 hours (thiamazole).
Chemical Structure

Chemical Structure Image
Carbimazole

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 31072, Carbimazole. https://pubchem.ncbi.nlm.nih.gov/compound/Carbimazole. Accessed June 28, 2022.

Storage
Store below 25°C. Protect from moisture.
MIMS Class
Antithyroid Agents
ATC Classification
H03BB01 - carbimazole ; Belongs to the class of sulfur-containing imidazole derivative agents. Used in the management of thyroid diseases.
References
AFT Pharmaceuticals Ltd. Carbimazole 5 mg Tablet data sheet 10 December 2020. Medsafe. http://www.medsafe.govt.nz. Accessed 06/04/2022.

Anon. Carbimazole. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 06/04/2022.

Buckingham R (ed). Carbimazole. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 06/04/2022.

Carbimazole 10 mg Tablets (Amdipharm UK Limited). MHRA. https://products.mhra.gov.uk. Accessed 06/04/2022.

Carbimazole Film-coated Tablets 5 mg (Remedica [HK]). MIMS Hongkong. http://www.mims.com/hongkong. Accessed 22/06/2022.

Joint Formulary Committee. Carbimazole. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 06/04/2022.

Neomercazole 20 (Amdipharm UK Limited). MHRA. https://products.mhra.gov.uk. Accessed 06/04/2022.

Neomercazole Tablet (A. Menarini Singapore Pte. Ltd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 22/06/2022.

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 © 2022 MIMS. All rights reserved. Powered by MIMS.com
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