[Accidents attributable to carbimazole in the treatment of Basedow's disease]

A series of 365 patients (330 women, 35 men) followed up for 9 years during treatment with 20 to 70 mg/day of carbimazole for an average duration of 18 months (range: 2 months to 6 years) was analyzed to evaluate frequency and type of accidents imputable to this synthetic antithyroid agent. Etiopathogenicity of these incidents is reviewed based on reports in the published literature. The product was extremely well tolerated by 349 patients. Minor side effects (hematologic in 0,8%, cutaneous in 1,4% and digestive in 1,6% of cases) were reported in 14 cases (3,8% of cases) and interruption of carbimazole treatment was necessary in 7 of these patients. Major accidents of favorable outcome (Lyell's syndrome, agranulocytosis) were observed in 2 patients (0,6% of cases). Two hypotheses can be evoked to explain their origin: a toxic cause mainly for the hematologic complication or an immuno-allergic mechanism suggested by the rapid onset of complications after beginning treatment. Carbimazole should not, therefore, be considered as a product lacking risks and the accidents observed strongly suggest the need for biological and particularly strict clinical surveillance of patients treated, the appearance of any sign of infection necessitating immediate full and differential blood counts and discontinuation of all therapy.