One can could* purchase amoxicillin without a prescription, AFAIK, as well as many other medications not considered controlled drugs or narcotics. The latter are more difficult to purchase - even Clarityn "D" is more controlled.

In some large "first class" pharmacies, you might even find a physician who will write prescriptions and administer injectable drugs. A friend gets his drugs from Mexico- made in Sweden, $600 a month's dosage in the USA, $50 in Mexico. And he's on Medicare , but his meds fall into a category that doesn't help him with the costs.

Deal with established "Farmacia de 1a Clase" establishments; for some drugs, they may have to order them from their jobbers if they're not on hand; this could take a day or even two.

*See sw3 below.