(and dosage form):
Each tablet contains: Carbimazole 5 mg
A 21.12 Hormone inhibitor.
Carbimazole is an anti-thyroid substance which depresses the formation of thyroid hormone. It reduces the uptake and concentration of inorganic iodine by the thyroid but its main effect is to reduce the formation of di-iodotyrosine and thyroxine. Carbimazole is absorbed rapidly from the gastro-intestinal tract and is widely distributed throughout the body. Carbimazole is completely metabolised to methimazole and it is the metabolite that is responsible for its clinical activity.
Carbimazole readily crosses the placental barrier and also attains a high concentration in the milk of lactating patients.
Excretion in the urine is rapid. The elimination half-life of methimazole may be increased in hepatic and renal impairment.
NeoMercazole tablets are indicated in the management of hyperthyroidism, thyrotoxicosis (including thyroid storm), and also for the preparation of patients for thyroidectomy.
NeoMercazole tablets can also be used in combination with radio-active ablative therapy.
Hypersensitivity to carbimazole or other thiourea antithyroid agents.
Carbimazole should be given with the utmost caution, or not at all, if there is any degree of tracheal obstruction, as high dosages may produce thyroid enlargement and obstructive symptoms may become marked.
DOSAGE AND DIRECTIONS FOR USE:
10 mg to 60 mg daily according to the severity of the disorder. The dose should be gradually reduced to the smallest amount which will control the disease. Daily dosage should be divided.
SIDE-EFFECTS AND SPECIAL PRECAUTIONS:
Carbimazole may be given during pregnancy to a thyrotoxic patient, but the smallest effective dose should be used lest overdosage adversely affects the foetus. Carbimazole crosses the placenta and is excreted into the breast milk. Carbimazole may, therefore, cause foetal or neonatal hypothyroidism and goitre.
Adverse effects occur most frequently during the first 8 weeks of treatment.
Side-effects may include rash, pruritis, skin pigmentation, paraesthesias, urticaria, headache, arthralgia, and gastro-intestinal disturbances (including nausea, vomiting and gastric discomfort), and abnormal hair loss.
Drug fever, a lupus-like syndrome, vasculitis and nephritis, and hepatic disorders, most commonly jaundice, and taste disturbances following carbimazole therapy have been reported.
Bone-marrow depression may occur and mild leucopenia is common. Dose-related agranulocytosis has been reported and patients should be warned to report the incidence of mouth ulcers or sore throat, fever, or rashes as they may precede abnormal findings in the blood by several days.
Treatment should be discontinued if there is any clinical or laboratory evidence of neutropenia. Pancytopenia / aplastic anaemia has been reported infrequently, as has thrombocytopenia and hypoprothrombinaemia.
Cross-sensitivity with other anti-thyroid agents may occur.
Isolated cases of myopathy have been reported. Patients experiencing myalgia after the intake of NeoMercazole should have their creatine phosphokinase levels monitored.
Carbimazole may interact adversely with other medicines. Iodine or iodine excess may decrease the response to NeoMercazole, requiring an increase in dosage or longer duration of therapy with antithyroid agents. Amiodarone contains 37% iodine by weight, and therefore its use significantly increases iodine intake, iodine deficiency may increase response to antithyroid agents, requiring a decrease in dosage or shorter duration of therapy.
As thyroid and metabolic status of patient decreases toward normal, response to oral anticoagulants may decrease, however, if thioamide-induced hypoprothrombinemia occurs, anticoagulant effect may be enhanced. Adjustment of oral anticoagulant dosage on the basis of prothrombin time is recommended. Serum concentrations of digoxin and digitoxin have been reported to increase as the thyroid and metabolic status of patients taking antithyroid agents decreased, reduction in dosage of any digitalis glycoside may be necessary as patients become euthyroid.
Antithyroid agents may decrease thyroidal uptake of sodium iodide I 131, a rebound increase in uptake may occur up to 5 days after sudden withdrawal of NeoMercazole.
Laboratory value alterations:
With diagnostic test results:
NeoMercazole may decrease thyroidal uptake of sodium iodide I 123 or I 131, or pertechnetate, withdrawal of NeoMercazole 5 days or more before radioactive iodine uptake tests is necessary to prevent interference.
With physiology laboratory test values:
Alanine aminotransferase (ALT [SGPT]) serum concentrations, Alkaline phosphatase serum concentrations, Aspartate aminotransferase (AST [SGOT]) serum concentrations, Bilirubin serum concentrations, Lactate dehydrogenase (LDH) serum concentrations and Prothrombin time (PT) may be increased, and may indicate hepatoxicity and be associated with splenomegaly.
KNOWN SYMPTOMS OF OVERDOSAGE AND PARTICULARS OF TREATMENT:
Overdosage or accidental poisoning may result in hypothyroidism and goitre. If blood dyscrasias occur, the drug should be immediately withdrawn. Further treatment is symptomatic and supportive.
Pale pink, circular, biconvex, mottled tablet, engraved "Neo/5" on one side. When broken into two it contains a white inner core which is centrally placed.
Containers of 100 tablets.
Store in a cool place below 25°C.
Keep tightly closed. Store in the original container.
KEEP OUT OF REACH OF CHILDREN.
G.3021 (Act 101/1965)
NAME AND BUSINESS ADDRESS OF THE APPLICANT:
DATE OF PUBLICATION OF THIS PACKAGE INSERT:
29 June 1988
Updated on this site: October 2004
Source: Community Pharmacy
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