As sdn1977 said, the first thing you have to do is figure out the situation. Many times, there may not be an error. And, if there is, it may or may not be an error on the part of pharmacy staff. I allways try to be friendly and helpful, show that I am making an effort to investigate the situation, and keep the patient informed of what is going on and what steps I have taken to find out if an error has occurred. That can involve things like pulling a hard copy, comparing the current NDC to what was filled last month, comparing the contents of a bottle to what is stocked ont he shelf, etc. People are less likely to sue or complain to the state board in a situation where they like their provider and when they feel that steps have been taken to prevent an error from occurring. Studies have shown that you are less likely to be sued if you admit an error than if you try to cover it up. So, I am honest about what has happened. You usually want to make disclosures in a place where others are unlikely to overhear the conversation. Of course, errors have to be fixed. And, if the error had other consequences, those have to be dealt with too. I don't typically reimburse copays. That seems to provide an opportunity for people to make a huge stink. And, in cases where that reimbursement has happened, I find that people never return to my store.
Luckily, it's not a problem I have had to deal with often at my current store.
One place I worked, the pharmacy manager's policy was "we don't make mistakes". She had blinders on. You will make mistakes if you practice long enough, no matter how good you are. And, you don't get to pick the magnitude of your errors. That is why we have to stay vigilent and follow up on patient concerns so that hopefully mistakes get caught before they have consequences.