I've not a clue.
The fact that the FDA unapproved the drug is a verifiable fact. The statement that hospitals use it daily is a verifiable anecdote.
This fact, though, instantly shut down the doctor whom I was arguing with while my wife lay there in labor. My wife wouldn't let anyone into the delivery room but me-- certainly not our attorney, if we had had one.
;-)
It's termed an "off-list" use. Puppy breeders quit using it a long time ago because there were too many damaged puppies.