I know that on most Domestic US flights, doctors, nurses, and paramedics are not permitted to open the medical bag unless their identity (and license) are confirmed by a flight medical group, and even at that, in situations where there is no doctor on the flight (but a paramedic or RN is), they will act upon the authority of a ground based doctor who approves all medication use.

In 2004, I was on a flight from CMH -> SJC and there was a medical emergency. At the time, I was a licensed paramedic, and pressed my call button when there was a page for 'medical personnel on the flight' after some delay when nobody else pressed their button. A flight attendant came up, asked me what my training was, and went to the front to call somewhere. A few minutes later, she brought a bag and took me to the back galley and handed me an airphone with a doctor on the other end, who confirmed with me the proper dosing and timing of ACLS drugs as we worked together to stabilize a patient. The process itself was like riding around with a doctor in the back of an ambulance -- he was very methodical about asking questions and quickly approved medication within reason at my discretion.

Ultimately, the flight was diverted, the patient was (very quickly) offboarded from the back galley and after some fuel for the plane, we were back on our way to SJC.

US Airways gave me a fair amount of miles (50K? 100K? I don't remember the exact number), upgraded the rest of my flight to first class, and provided me Platinum status for the rest of the year, along with a few other trinkets/swag pieces.