When I first signed up for Medicare in 2010, I used the Plan D calculator to find a plan that had no yearly deductible and yet had a monthly premium I could afford. I then used the drug calculator on the medicare website and found that by using the insurance and based on the brand-name drugs I was taking, I would hit the donut hole in May and then would have to pay full retail until I hit $4,700 in out of pocket costs. I then went to my GP and we discussed the various drugs and switched to the least expensive generics wherever possible. I now use the insurance for only the most expensive of the drugs, one which does not have a generic equivalent. I checked a couple of drugstores, but decided to use Costco for the generics which keeps those costs down. There are other places (like the wicked Walmart) that has very inexpensive generics, but, just as a personal matter, I would never, but never go to a Walmart, even if they were GIVING the stuff away. So far, this plan has worked out just fine for me.
As an example of how it is working, there was one drug I had been taking for quite some time that the price (even at Costco) tripled in one month. Went back to the doctor and got a prescription for the same class of drug, different name, different manufacturer which brought the cost down again.
The donut hole will not disappear until 2020. By then, the pharmaceuticals will have bought enough congress critters to change the laws again to further squeeze money out of our pockets.