When a pharmacist notices that a medication is being refilled sooner than needed on many occasions, than the pharmacist will notify the prescribing doctor and inquire if the prescription has been changed. This especially is true for narcotic medication. Misuse of medications is a very common problem with the elderly who sometimes do not understand the doctors instructions.
Pharmacists are also very vigilant when it comes to narcotic medications, not only do they notify the prescribing doctor, but they also notify neighboring drug stores who will make a record of the patient and keep an eye out for a patient who goes to different pharmacies to refill their prescriptions.
A pharmacist will also notify the DEA if they feel that the ordering doctor has a habit of prescribing a large quanity of narcotic medication.
I hope that this answers your question