In the past, I have requested prescriptions from my physician when I was going off to some third-world country and I would be a long way away from any first-class medical care or drugs.
I generally request one broad-spectrum antibiotic such as Bactrim/Cipro, one prescription strength painkiller (minimum Tylenol-codeine), and often Diamox for high altitude. I have encountered some resistance from the physician, but not for the reasons you might expect. He was resistant to Diamox because he thought of it only for treatment of some heart disease, and he was not familiar with it for high altitude illnesses. That was way back in 1997, so I will cut him some slack on that one. The other two were no problem, as long as you can explain why you want them and under what circumstances you would take them. Often the physician can suggest a drug somewhat better than what you had in mind. My current physician and I have a good rapport, so I can simply call him and he will send the prescription message to the pharmacy without ever seeing me.
Strangely, I have given away much more Diamox than I have ever consumed, and I gave it away to a mountain guide. Go figure.
Now when I am out solo in the Sierra Nevada, I will carry some old leftovers from these prescriptions, but I would consume them only in a dire emergency. Some of this stuff goes stale quickly.
Flagyl would be another drug to think about.