If you ever need to get medicine, toiletries and other personal items while travelling in Toronto, the best place to grab them are:
1 - Shopper's Drug Mart (pharmacy chain): price wise Shopper's is probably the most expensive as well. But this is by far the biggest brand of pharmacy at least in Ontario.
2 - Rexall (pharmacy chain): pretty much the same as Shopper's, lots of locations too. Prices may be a little cheaper than Shopper's.
3 - Loblaws (grocery store): not too many locations, but if you're close by one they pretty much sell everything you need
4 - Walmart: no description needed. Their locations are mostly in the suburbs
Best way to find them is to use Google Maps to find where they are located. I found Google Maps has a very good database of their locations. Shopper's and Rexall have lots of locations downtown, whereas Loblaws and Walmart is mostly in the suburbs.