[Effect of intravenous methimazole on serum levels of thyroid hormones in patients with hyperthyroidism resistant to oral thyrostatic drugs].

The effectiveness of therapy involving intravenous administration of methimazole applied in patients with hyperthyroidism resistant to oral thyrostatic drugs has been investigated. Methimazole (Favistan, Asta) was administered intravenously to 3 patients (two women and one man, of ages 21, 24 and 67 years, respectively) in whom there was no remission of the disease after oral methimazole therapy lasting at least two months. Blood serum concentrations of thyroxine (T4), triiodothyronine (T3), reverse++ triiodothyronine (rT3) and triiodothyronine binding index (T3I) have been measured and free thyroxine index (FT4I) calculated before the treatment and on the 4-th, 7-th, 11-th, 14-th and 17-th day of the treatment. The mean value of T4 concentration decreased from 17.0 micrograms/dl before the treatment to 9.7 micrograms/dl after the treatment. T3 from 352 to 177 ng/dl, rT3 from 114 to 103ng/dl the value of T3I from 183 to 161%, and that of FT4I from 30 to 17, respectively. A significant fall of T3 level was observed on the 11-th day of the therapy, that of rT3 on the 14-th day, and that of FT4I on the seventh day. It was concluded that the resistance of some patients with hyperthyroidism to the oral thyreostatic therapy may be caused by the defective absorption of these drugs from the intestinal tract.