My presentation this afternoon will cover two primary topics. The first is a background or a description of why levothyroxine sodium was declared a new drug in 1997. I'll discuss specific aspects of the guidance for industry for this product. The second part of the presentation will focus on the FDA's current recommendation for evaluating bioequivalence between these levothyroxine products, and at that time, when I discuss that section, I'll talk about the recommended study design and on the bioequivalence analysis itself.
Well, prior to August of 2000, levothyroxine sodium was an unapproved marketed drug. It had actually been grandfathered in. It was introduced in the 1950s as a more pure synthetic form of thyroid, USP, and in 1997, it was estimated that there were at least 37 manufacturers or repackagers of levothyroxine sodium tablets.
However, despite the fact that we had more than 40 years of clinical experience with this particular product, there was still a high degree of uncertainty about the products themselves and the uncertainty existed with all of the products that were currently on the