The insurance company can investigate the efficacy of prescriptions and stop paying for ones that don't work. The article says some of them have done exactly that with Oxycontin.
At the other end, if the pain killer isn't working, a patient can go to a different doctor who will prescribe something else.
Right, but I am spending the money of my company. They control my salary and advancement, and I also have a fixed pool to draw from.
Doctors are spending money for insurance companies.