I think it is best to avoid anti-biotics for stomach bugs or diarrhea unless it is extreme or unless you have an actual parasite that will probably not leave on its own accord i.e. the India backpackers favourite - Giardia. Taking powerful anti-biotics kills everything. It really should be a last resort. Likewise, Immodium can cause problems as it undermines your bodies natural defenses, another last resort then.
Exercising caution when choosing places to dine out and implementing some sort of decent water filtration would be wise, as prevention is always the best cure. Also, the worldwide overuse of anti-biotics undermining their effectiveness. I also feel if I can get through a bout of the runs without them that I`m taking one for the team
As for Valium, that is a really useful drug to have around but yes I can attest to it being highly addictive. It is annoying that they are restricted in Europe, for as Ted says, they are fantastic for long-haul flights, and turn an otherwise cramped 14 hour flight into a pretty good party, especially combined with two, three, four or five plus complimentary gin and tonics - after which I find everything makes perfect sense
Iodine liquid is the best anti-septic in my experience, especially for the tropics where cream-based treatments are ineffective. Plus you can purify water with it - great stuff! Only problem is that is it quite hard to find, definitely stock up before you leave.