Brand name Neo-Mercazole
Used in the following combined preparations None
GENERAL INFORMATION
Carbimazole is an antithyroid drug used to suppress the formation of thyroid hormones in people with an overactive thyroid gland (hyperthyroidism). In some people, particularly those with Graves’ disease (the most common form of
hyperthyroidism), drug treatment alone may relieve the disorder.
Carbimazole is also used in more serious cases, for example, to restore the normal function of the thyroid gland before its partial removal by surgery, or to intensify the absorption of radioactive iodine when that cell-destroying drug is used. Carbimazole also prevents the harmful release of thyroid hormone that can sometimes follow the use of radioactive iodine. Because the full benefits of this medication are not felt for several weeks, beta blockers may be given during this period to help control symptoms. Maintenance treatment may be continued for as long as 18 months unless surgery or radioactive iodine is used.
Occasionally the carbimazole dose is kept high and thyroxine is also prescribed in order to prevent a goitre from developing.
INFORMATION FOR USERS
Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.
How taken
Tablets.
Frequency and timing of doses
2-3 x daily.
Adult dosage range
Usually 30mg daily; in severe cases this may have to be increased to 60mg. Once control is achieved, dosage is reduced gradually to a maintenance dose of 5-15mg.
Onset of effect
Some improvement is usually felt within 1-3 weeks. Full beneficial effects usually take 4-8 weeks.
Duration of action
12-24 hours.
Diet advice
Your doctor may advise you to avoid foods that are high in iodine.
Storage
Keep in a closed container in a cool, dry place out of the reach of children.
Missed dose
Take as soon as you remember. If your next dose is due, take both doses together.
Stopping the drug
Do not stop the drug without consulting your doctor; symptoms may recur.
Exceeding the dose
An occasional unintentional extra dose is unlikely to cause problems. Large overdoses may cause nausea, vomiting, and headache. Notify your doctor.
POSSIBLE ADVERSE EFFECTS
Serious side effects are rare. A sore throat or mouth ulcers may indicate adverse effects on the blood and require prompt medical attention.
INTERACTIONS
None.
QUICK REFERENCE
Drug group Antithyroid drug
Overdose danger rating Medium
Dependence rating Low
Prescription needed Yes
Available as generic No
SPECIAL PRECAUTIONS
Be sure to tell your doctor if:
You have long-term liver or kidney problems. You are taking other medications.
Pregnancy
May be associated with defects in the baby. However, the risk to the baby of untreated hyperthyroidism is higher. Discuss with your doctor.
Breast-feeding
The drug passes into the breast milk, but mothers may breast-feed as long as the lowest effective dose is used and the baby is carefully monitored. Discuss with your doctor.
Infants and children
Reduced dose necessary.
Over 60
No special problems.
Driving and hazardous work
Avoid such activities until you have learned how carbimazole affects you because the drug may cause dizziness.
Alcohol
No known problems.
PROLONGED USE
High doses over a prolonged period may reduce the production of blood cells by the bone marrow.
Monitoring Blood cell counts are carried out, and periodic tests of thyroid function are usually required.
