a couple of points (I used to moonlight retail - but predominately hospital career)
1. DO NOT send them to my ER because they ran out of medications unless it is an absolutely last resort. They can call their MD - somebody should be oncall for them, if that fails, go to URGENT care first, it is MUCH cheaper and MUCH more appropriate.
2. There are two types of people that this happens to - those they are just ignorant and have the ability to take care of themselves, and those that for whatever reason don't (elderly, demented, etc)
3. If you don't have a record of rx's for them (meaning they are not your patient) you do have the potential for liability. There was a sting once where members of the board of pharmacy went around with emtpy rx bottles begging for a refill using this story and then proceeded to file charges if they filled it - complete BS - but it can happen
4. They have the ability to get a RX - charge them cash if it is a cheap med, it is an expensive med, offer them cash, or process with ins with override