An incredible idea. Very proud to see new sustainable models for nonprofits going through YC, especially ones that actually save lives.
I've always thought Medicare would jump at the idea of slashing its drug costs, but undertaking something like this is a crazy huge project.
It's more a matter of whether your country's regulator lets them in, and/or if you have enough retail competition to drive down prices close to their actual cost.
Be careful as some medications are very moisture-sensitive, light-sensitive or oxygen-sensitive.
For example: http://www.fda.gov/Drugs/DrugSafety/ucm248746.htm