Management of hyperthyroidism, thyrotoxicosis (including thyroid storm), & also for the preparation of patients for thyroidectomy. It can also be used in combination with radioactive ablative therapy.
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.
Adults: The initial dose: 20 - 60 mg, in 2-3 divided doses until the patient is euthyroid. Daily dosage should be divided. Maintenance regimen: Dose is gradually reduced to maintain a euthyroid state. Final dosage is usually in the range of 5 - 15 mg/day which may be taken as a single daily dose. Neonates & Children below 12 years: The usual initial dose is 250 mcg /Kg/day in divided doses. Duration of treatment: 18 to 24 months
Carbimazole may interact adversely with other medicines. Iodine or iodine excess may decrease the response to Carbimazole, requiring an increase in dosage or longer duration of therapy with antithyroid agents. As thyroid and metabolic status of patient decreases toward normal, response to oral anticoagulants may decrease, however, if thioamide-induced hypoprothrombinemia occurs, anticoagulant effects 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.
Patients with known hypersensitivity to Carbimazole or other thiourea antithyroid agents.
Mild leucopaenia, sore throat, mouth ulcers, fever, bruising, malaise; rarely cholestatic jaundice; nephrotic syndrome. Nausea, loss of taste, headache, arthralgia, alopoecia. Agranulocytosis, aplastic anaemia, hypoprothrombinaemia, neutropaenia; hypothyroidism & goitre.
Recommended but the smallest effective dose should be used least overdosage adversely affects the foetus.
Overdose 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.
Keep below 30°C temperature, away from light & moisture. Keep out of the reach of children.
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