You should ask your doctor, a quick phone call might be all that is needed.
I have no direct experience with the medications you mention, but can say my insurance requires (or I pay a big cost penalty) me to use generic drugs. These are, however, US distributed.
I believe many people buy drugs from Canada to save money, but I have my doubts about the quality of anything that can be ordered over the Internet without a prescription...assuming a prescription is required in the US. Again, I have not experience, I have prescription insurance and purchase all through my insurance supplier. I have purchased generics from Walmart (there are others) that were very inexpensive. Warfarin was what I purchased. This is not an advertisement for Walmart, I thing there are several pharmacies that offer a limited list of generics at very low cost. $10 comes to mind for a 30 day supply. But, again, the list is limited.