How many prescriptions for narcotics can you get filled before the DEA sends your dr a certified letter?

And is the person notified about the certified letter or are they suprised about it when the got to the DR’s office or pharmacy? I watched intervention last night and this women who severely abused prescription drugs was on the show and her sister mentioned that she was on some DEA’s list but, was still able to get prescriptions and fill them. I’m just baffled.

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