I have no idea what the US laws are like. In terms of my Professional Hunters License I can carry two ampules of Morphine (or Pethedine) and any antibiotics I like. I can also write a script for any client for bilhazia or malaria treatment. That said, Most clients seem to be able to get their GP's two write them up for some serious (modern) pain killers - like endocet and a months supply of suitable antibiotics.
But- as part of the process to get A PH license you have to do an advanced first aid course and keep it current (which means a weeks refresher every 3 years). In terms of long term survival, a good, practical nurse is probably more important than a family doctor who only prescribes drugs...for short term, a trauma first aid man who can get a drip into a vein that has collapsed is the man you want around.