Bioequivalence and Bioavailability Forum

Hi nobody,

❝ L-Thyroxine (as an endogenous aminoacid with strong hormonal effects) is somefing very special, as recognized long ago, e.g.: […]

Sure. Dose finding for levothyroxine is a pain in the back (NTID, long half life, large between-subject variability). Hence, most endocrinologists would not switch their patients from one product to another one.
Note that the FDA’s guidance is even less stringent than the EMA’s. In the study of Gottwald-Hostalek et al. the CV_intra of C_max was 17.7%. According to the FDA’s RSABE (assuming CV_wT=CV_wR) that would translate into implied BE-limits of 83.11–120.33%…
I think that neither physicians nor patients were aware of what was going on – that wasn’t a product-switch but a change in the formulation. Both thought to take still the same product of the same manufacturer.