That's not actually true Taz. As I posted in a different thread, compounding pharmacies exist, and they do make up compounds from otherwise legally available pharmaceutical raw materials, precisely in circumstances where the patient's needs can not be met by FDA approved and commercially available drugs. So long as they follow the specific federal regs governing compounding pharmacies, they are
exempt from the FDA "new drug" approval process. (See,
Medical Ctr Pharmacy vs. Mukasey (5th Cir. , July 18, 2008). Medical Ctr Pharmacy vs. Mukasey - U.S. Court of Appeals for the 5th Cir. - July 18, 2008, Federal Circuits, Docket 06-51583 - vLex
And doctors do write prescriptions for compounded medications in cases where there are no appropriate FDA approved drugs for a particular patient and/or circumstance.
I'm not saying that a doctor would write a prescription for something to be imported, as the OP was referring to, but I do know that they will write scripts for "unapproved" specially compounded medications.