Surprisingly not often because the neighborhood I work at is mostly medicaid and medicare patients so the pay isn't too bad. There is very few people with actual insurance and in those cases we can barely get away with breaking even depending on the medication. The doctors here have their own formulary they select off of and if something pays terribly for us, we give a call to the front desk and ask if we can change to ___. For the most part, if the change is based off a that list they gave the front desk, they just say yes to the change without needing to call the doctor. Examples being omeprazole > esomeprazole or mucinex 600 > 400mg. Two doctors here even lets us freely change between drugs of same class as long as doses match (Probably has too much trust in us). One of them just wants us to notify them of changes so they send refill scripts matching the change.