In Mexico (and probably other countries), Lomotil and antibiotics like Cipro and another which offers a full course in just 3 tablets are sold without a prescription in drugstores. Lomotil is used there by “most people” for Touristas (aka Montezuma’s Revenge, aka the Aztec Two Step). I have brought these items back to the States from there.

Other pharmaceuticals are sold such also; but, I probably would not want to carry some of these across the border without a good reason.