active ingredient and that's where T4 fits in. TSH, on the other hand, would be relegated to the third or fourth category.
As was made very clear in the previous presentation, using total thyroxine without a baseline correction is insensitive for conducting bioequivalence studies with levothyroxine sodium tablets and the FDA completely concurs. Rather, a baseline correction method whereby the mean of three pre-dose samples is subtracted from all of the subsequent post-dose samples. This is the preferred method and it is adequately sensitive for evaluating levothyroxine bioequivalence.
Now, when the agency decided to adopt a baseline correction method for bioequivalence, we went back to data from the six original NDA applications. Dosage from proportionality studies from four the six NDAs were re-evaluated using the baseline correction method and they're presented here.
Let me orient you to this slide. On the left-hand side, we have four products, 1, 2, 3 and 4. The first two columns are AUC and the second two columns are Cmax. This is a three-way crossover study. The dose that