[Severe adverse effects of low-dose carbimazole treatment in hyperthyroidism. A retrospective study of 476 patients]

A material of 476 hyperthyroid patients treated with carbimazole and 69 patients treated with PTU in the period from 1978 to 1986 were studied retrospectively. The antithyroid treatment was given in low dosage without supplementary thyroxine. The total frequency of adverse effects, defined as symptoms leading to discontinuance of the treatment, was 8.0% for carbimazole and 2.9% for PTU. There were no cases of agranulocytosis in the group treated with carbimazole, and one case in the group treated with PTU. No relationship between age and adverse effects could be demonstrated. The relationship between adverse effects and dosage is discussed, and it is concluded that low dosage treatment with carbimazole has a very low frequency of adverse effects in terms of agranulocytosis and toxic hepatitis.