1) Lay out the criteria for choosing drugs to buy.
2) Convene regular meetings to review possible purchases ("Which drugs meet our criteria?").
3) Document decisions to either purchase or not purchase.
4) Establish an inventory tracking system.
5) Perform periodic audits to either identify losses, or to recommend re-purchasing to replace expired items.
Standard activity. Very standard. Absolutely expected in any government effort.
And, No, the government almost never actually does any of that stuff. It's on the books -- they are mandated to basically follow those steps. And they just don't.
OR hand the job over to Walmart...