More often that not the reason it would not be FDA approved is because the company had no interest in doing a clinical trial to determine the meat withdraw time, or how long any of the chemical derivatives would persist in the meat. The cost of this kind of research is very high.
In vet medicine, just about every medication or treatment that is approved for use in food animals has a meat or milk withdraw time, where the animal can not be harvested until that period has passed.
