Adverse reactions usually occur in the first eight weeks of treatment. The most frequently occurring reactions are nausea, headache, arthralgia, mild gastric distress, skin rashes and pruritus. These reactions are usually self-limiting and may not require withdrawal of the drug.
The undesirable effects are listed below by system organ class and the following frequency convention: Not known (cannot be estimated from the available data). Blood and lymphatic system disorders Bone marrow depression including neutropenia, eosinophilia, leucopenia and agranulocytosis has been reported.
Fatalities with carbimazole-induced agranulocytosis have been reported. Rare cases of pancytopenia/aplastic anaemia and isolated thrombocytopenia have also been reported. Additionally, very rare cases of haemolytic anaemia have been reported.
Patients should always be warned about the onset of sore throats, bruising or bleeding, mouth ulcers, fever and malaise and should be instructed to stop the drug and to seek medical advice immediately. In such patients, white blood cell counts should be performed immediately, particularly where there is any clinical evidence of infection.
Generalised lymphadenopathy. Immune system disorders Angioedema and multi-system hypersensitivity reactions such as cutaneous vasculitis, liver, lung and renal effects occur. Endocrine disorders Insulin autoimmune syndrome (with pronounced decline in blood glucose level).
Nervous system disorders Headache, neuritis, polyneuropathy. Vascular disorders Bleeding Gastrointestinal disorders Nausea, mild gastrointestinal disturbance. Loss of sense of taste has been observed. Acute salivary gland swelling. Acute pancreatitis.
Hepatobiliary disorders Hepatic disorders, including abnormal liver function tests, hepatitis, cholestatic hepatitis, cholestatic jaundice and most commonly jaundice, have been reported; in these cases, carbimazole tablets should be withdrawn.
Skin and subcutaneous tissue disorders Skin rashes, pruritus, urticaria. Hair loss has been occasionally reported. Severe cutaneous hypersensitivity reactions have been reported in both adult and paediatric patients, including Stevens-Johnson syndrome (very rare including isolated reports: severe forms, including generalised dermatitis, have only been described in isolated cases).
Musculoskeletal and connective tissue disorders Isolated cases of myopathy have been reported. Patients experiencing myalgia after the intake of carbimazole should have their creatine phosphokinase levels monitored. General disorders and administration site conditions Fever, malaise.
Injury, poisoning and procedural complications Bruising Paediatric population Frequency, type and severity of adverse reactions in children appear to be comparable with those in adults. Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important.
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