FDA's decision to leave Avandia rosiglitazone on the market with extraordinary restrictions on its use, a pathway for obtaining data that could lead to an easing of the restrictions, and a commitment from GlaxoSmithKline plc to cease promoting the diabetes drug, serves as a model for how critical elements of an adaptive approval system could work.

The steps announced last week are the most vivid example of how the regulatory flexibility created by the FDA Amendments Act of 2007 allows the agency to move from a black-and-white stance in which investigational drugs are considered dangerous and approved drugs are treated as safe to a nuanced position in which access and use restrictions can be adjusted. As such, they could provide insight into how FDA might deal with similar situations in the future.