Vet Man - insurance companies do audits frequently. If its a medication that it's known dosage is once a day (a 24 hour extended release tablet for example) and the doc writes it for 3/day, it creates a flag at the insurance company. The insurance company calls the pharmacy and requests a copy of the rx and documentation from the pharmacy for the excessive dose. If none is had, call the doc. Doc then has to provide documentation that the dose is necessary. If he is unable to do so, the pharmacy gets reverse billed for the med, plus a fine or fee. The md can be fined and the patient risks losing his coverage.
And if it's a Medicare drug plan, the pharmacist will be paying the fine out of his pocket, which could be up to $10,000 PER INCIDENT. So if he refilled the rx 5 times, it's a $50k fine. The doc also risks losing his ability to bill for Medicare services.
Does it happen often? No. But audits like those (especially Medicare) are not fun. And it doesn't have to be an overtly egregious abuse to flag an audit.