[Bioequivalence of L-thyroxine tablets and a liquid L-thyroxine solution in the treatment of hypothyroid patients].
OBJECTIVE
The therapeutic equivalence of L-thyroxine (T(4)) tablets and a new liquid T(4) solution was investigated in patients with hypothyroidism.


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.


CONCLUSIONS
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.
Grussendorf
Martin
M
Endokrinologie und Diabetologie im Zentrum, Stuttgart. martin@grussendorf.de
Vaupel
Renate
R
Wegscheider
Karl
K
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D016001:Confidence Intervals; D003627:Data Interpretation, Statistical; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012996:Solutions; D013607:Tablets; D013810:Therapeutic Equivalency; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood
D012996:Solutions; D013607:Tablets; D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine