a manufacturing overage. It's a very important distinction because a stability overage is intended to extend the shelf life of the product and we saw a lot of that and that's not acceptable to the agency, whereas a manufacturing overage is sometimes necessary to account for some of the loss during the manufacturing process itself.
In 1987, Fish described overages in levothyroxine products as high as 9 percent. The FDA actually has internal documentation that would suggest that in some cases, these stability overages were actually as high as 15 percent.
The FDA also has evidence that significant changes were being made to the product formulations in an attempt to improve product stability, and these changes were to both the amounts of the active drug and also to the amounts of the product components.
There was also evidence from case reports in the literature that suggested that therapeutic failures had occurred when patients had received a refill of the same product for which they had been previously stable. Of the 58 cases of therapeutic failure reported to the FDA