Also, when they can get away with it, they tell the manufacturer that they're going to sell at a set price or the Canadian government will open a factory and make the drug themselves.
It's not just Canada...there are several countries that are pulling this same blackmail. Consequently, the price Americans pay for many drugs is artificially high: essentially we subsidize the drug costs of socialized medicine countries that are underselling drugs to their own populace.
The one sure way to make sure drugs don't get to the people who truly need them is for the government to impose price controls.