Food and Drug Administration official Dr. Lester Crawford quit his position just two months after he won Senate confirmation. It is still not clear why Crawford resigned. In his email to the FDA stuff he wrote that at the age of 67 he feels the time has come for him to step aside. He has been acting as deputy commissioner, acting commissioner and, as commissioner, for three and a half years at the FDA.
There are speculations that his resign has to do with problems regarding the safety of Vioxx and similar arthritis drugs and the FDA's ability to monitor the safety of medications already on the market and inability to make right decision about the emergency contraceptive plan B.

President George W. Bush quickly appointed an acting commissioner who will also continue in his current job as director of the National Cancer Institute.
The thing is that FDA does not need acting commissioners but full-time commissioner who will ensure that decisions about the safety and effectiveness of drugs available to the public will be based on credible science, and not influenced by political agendas.