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.
Nausea, headache, arthralgia, fever, jaundice, malaise, mild gastric distress, skin rashes, pruritus, taste disturbance; bone marrow depression including neutropenia, eosinophilia, leucopenia. Rarely, pancytopenia/aplastic anaemia and isolated thrombocytopenia, haemolytic anaemia.
Pregnancy Category D. There is positive evidence of human foetal risk, but the benefits from use in pregnant women may be acceptable despite the risk
Caution should be taken in patients with intrathoracic goitre. Mild to moderate hepatic impairment. Caution also should be taken in children, pregnancy and lactation.
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 If blood dyscrasias occur, the drug should be immediately withdrawn.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.
