It all depends on what medication you're needing. I would call around to US companies such as Medco, but also don't leave your your local grocery store, warehouse club or
walmart. They have many generics for only $4 a month.
I would strongly caution against ordering out of the country, although if you must Canada might be the safest choice, but I would wonder if you would save that much once shipping is figured in. I would stay far away from Mexico, India and any other country that would allow you to self diagnose by the means of Dr. Google.
Personally I'd like to thank those that decide what kind of infection they have, that it is really an infection that requires antibiotics and then decides after hours of Web MD what antibiotic would be best. This among other things has helped create these "super" bugs that are resistant to the more mild antibiotics.
I know that's probably not what you were asking, but just in case, please spend the $40 at Walgreens for the nurse there to decide if you even need an antibiotic. You don't have to fill the script there if you get one, they don't have $4 generics. You can ask for a printed script and take it to the pharmacy of your choice.