Pain medicine is very much like medicine as it was practiced in Rome from 300 BC-200 AD....anyone could be a doctor at that time with no training at all. Undertakers were hanging out shingles as physicians, there was no apprenticeship required, there was no formal training required. It wasn't until the 3rd century AD when medical school training was required, then that requirement went away after the fall of the Roman Empire and was not revived again until the medical school was established at Salerno in Italy in 1077 AD. Then only intermittently was medical school required in Europe and the US until the 19th century. Today we have no formal training requirements for interventional pain medicine. Nurses, without any training at all in school are doing it. FPs without formal training are doing fluoro procedures in their offices. Over half the ABMS board certified pain physicians had no formal training at all....they were given the certificate for passing a written test, thereby rendering the designation as "board certified" as meaningless. That being said, if you decide to do interventional pain procedures in your office or otherwise without any formal training and screw up, especially if you are a family practitioner or nurse, then you will find little sympathy in the expert witnesses that will line up to testify against you in court.
