Excellent question!
My BOB medical kit has Amoxicillin 500mg x 40.
Broad spectrum antibiotics are a prescription only medication.
They are also non-habit forming and not prone to abuse (can't get high on antibiotics!).
Therefore, my experience has been that a reasonable MD will write you a prescription if you explain why you want it.
TIP: use the phrase 'emergency preparedness' , not 'survivalist'!
Yes, they do have a limited shelf life, but they are also generic and therefore, cheap!
Also, bear in mind that once a medication, which does not need to be stored under special conditions (e.g. insulin), has reached it's 'Discard By' date, does not mean it becomes worthless. It just means that the potency of the med starts to decrease. Eventually you reach the point where they are useless, but 6 months after the use by date - still of great worth.
So, if the SHTF tomorrow and I needed to use my Amoxicillin which technically expired in October 2010, I would simply increase the dosage according to the amount of time it is past it's use by date.
Another interesting thing about 'human' antibiotics is that they can be used safely on your pet cat should the need arise.
Obviously, you need to decrease the dose mathematically according to body weight - too much will be toxic. But if a vet is not available for your 'kitteh', you can do this with caution.
Don't know about dogs - didn't bother to ask the vet because I hate dogs.
Message me privately if you want more info. Perhaps you can answer some questions or have some tips to share with me.
As per standard practice, don't believe anything you read in a forum - verify all info with your MD / Pharmacist / Veterinarian!
PS: If you find an MD who will write a prescription for pain meds for your BOB, please let me know!