estrogen products. The study would have to be a multiple dosing. It would have to be steady state, and you would really like to validate it with known differences.
Now, what marker to use? Well, physicians use free T4. They also use TSH. If we were to use those, though, you would have to define the maximally accepted changes in TSH are to ensure the physicians of their therapeutic equivalence.
So to conclude, small differences matter. Products that differ by 12.5 percent cannot be detected with the current criteria, and we fully believe that we should bring all the scientific prowess in academia, FDA, endocrine societies, and industry to consider the issues of how to construct proper evaluation of bioequivalence in these T4 products.
That concludes my presentation.
DR. JOHNSON: Well, this part of the presentation will now focus on the FDA's current recommendation for evaluating levothyroxine sodium bioequivalence. However, before I begin, I want to make a couple of comments with regard to some of the slides that we just saw from Abbott Laboratories.