Although I have no direct experience with purchasing, I am a Canadian, and it is a VERY big business, with Americans their biggest customers by far.

On average, prescription medications here are MUCH cheaper, for the same medications you're getting in the U.S..

The industry in Canada is very rigidly controlled and monitored by Government. You will have to provide prescriptions from your son's doctors, and may have to undergo a telephone interview as well
hope this helps
Wayne