Bioequivalence of L-thyroxine tablets and a liquid L-thyroxine solution in the treatment of hypothyroid patients

摘要

BACKGROUND AND PURPOSE: The therapeutic equivalence of L-thyroxine (T(4)) tablets and a new liquid T(4) solution was investigated in patients with hypothyroidism. PATIENTS AND METHODS: The study was unblinded, multicentric and prospective: 136 patients (with autoimmune thyroiditis, after thyroid surgery and/or after therapy with radioiodine), who had been treated with T(4) tablets, were switched to a treatment with a liquid T(4) solution (containing 5 microg T(4) per drop) in the same dosage. Thyrotropin (TSH) was measured after 1, 2, 3, and 6 months; the dose of the T4 solution was adapted to obtain a midnormal TSH level. RESULTS: The T(4) dose remained constant during the 6 months. Dose adaptations were necessary in 19-23% of patients at the different timepoints, with dose reductions and increases, respectively, becoming equally frequently necessary. The mean TSH level was 0.79 mU/l at the beginning and 0.81 mU/l after 6 months; similarly, the mean levels of free triiodothyronine (fT(3)) and free thyroxine (fT(4)) were equivalent.The liquid T(4) solution was well tolerated: adverse events were noted in three patients (1.8%); one serious adverse event (thyroid carcinoma) showed no correlation to the treatment. CONCLUSION: T(4) tablets and liquid T(4) solution have been proven to be therapeutically equivalent; the use of liquid T(4) solutions will have advantages in the treatment of hypothyroid infants or elderly patients with disturbed swallowing, patients who need a differentiated titration of the T(4) dose, as well as patients with an allergy against inactive ingredients of L-thyroxine tablets.