Carbimazole (antithyroid agent)

Carbimazole is an antithyroid drug. It treats hyperthyroidism or an overactive thyroid gland. An overactive thyroid can grow larger, forming a goiter.

Know the basics

What is carbimazole used for?

• Controlling hyperthyroidism
• Reducing the size of the thyroid prior to surgery

How should I take carbimazole?

Carbimazole is available as an oral tablet. The oral tablet should be taken by mouth without chewing or crushing it. The tablets can be taken with each meal, for your convenience.

How do I store carbimazole?

This product is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer. 

There may be different brands of this drug that may have different storage needs. So, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush this product down the toilet or pour them into a drain unless instructed to do so. Additionally, it is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Know the precautions & warnings

What should I know before using carbimazole?

Before using this drug, tell your doctor if you are/have:

Is it safe to take carbimazole during pregnancy or breast-feeding?

Carbimazole is a pregnancy category D drug and should not be given to pregnant women unless the benefits outweigh the risks. There is positive evidence it causes fetal defects.

It passes into the placenta and breast milk. Breastfeeding is safe when the mother’s dose is low. At higher doses, breastfeeding should be stopped.

Side effects and interactions

What side effects can occur when using carbimazole?

Like all drugs, this product may have side effects. If they occur, side effects are generally mild and resolve once treatment is finished or the dose is lowered. Some reported side effects include:

Seek medical attention immediately if you experience any of these serious, potentially fatal drug reactions:

• Bone marrow depression
• Agranulocytosis
• Pancreatitis
• Hemolytic anemia
• Thrombocytopenia
• Stevens-Johnson syndrome (SJS)

However, not everyone experiences these side effects. In addition, some people may experience other side effects. So, if you have any concerns about a side effect, please consult your doctor or pharmacist.

Interactions

What drugs may interact with carbimazole?

This medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. 

To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. 

Drugs with known interactions:

• Propylthiouracil (PTU)
• Thiamazole
• Anticoagulants
• Theophylline
• Prednisolone
• Erythromycin
• Digitalis
• Beta-blockers

If you experience an adverse drug interaction, inform your doctor immediately to reevaluate your treatment plan. Approaches include dose adjustment, drug substitution, or ending therapy.

Does food or alcohol interact with carbimazole?

This drug may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Do not drink alcohol while taking this drug. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with carbimazole?

This drug may interact with underlying conditions. This interaction may worsen your health condition or alter the way the drug works. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

• Pre-existing blood disorders
• Acute pancreatitis
• Hepatic impairment
• Tracheal obstruction
• Require radio-iodine imaging
• Intrathoracic goiter

Dosage

The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

What is the dose for an adult?

Hyperthyroidism

• Initially take 15-60 mg per day in 2-3 divided doses. Reduce the dose gradually once thyroid levels are normalized.
• Maintenance dose: 5-15 mg per day as a single dose.
• Blocking replacement: give 20-60 mg in 2-3 divided doses in combination with levothyroxine.
• Treatment duration: 6 to 18 months

What is the dose for a child?

Hyperthyroidism

• Ages 3 to 17 years: initially give 15 mg per day and adjust according to the response.

How is carbimazole available?

This drug is available in the following brands, dosage forms, and strengths:

• Carbinom 5 mg and 10 mg tablets
• NeoMercazole 5mg and 20 mg tablets
• Neomerdin 5mg and 20 mg tablets
• Neotrox 5 mg and 20 mg tablets

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

What should I do if I miss a dose?

If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.