Antibiotics are prescription only. As for alternatives, it depends on what your problem is as to which alternative you'd use.
You need a physicians prescriptions for antibiotics.
Get some bread, and grow your own.
Yes, in Mexico
Any Farm supply has Amimal grade. I use it cause having Veterans healthcare is like having nothing. I have to treat myself.
You can't get them over the counter in the US. There is nothing that is even close to antibiotics.
The reason that they aren't sold over the counter is that they can potentially be dangerous if used in the wrong manner.