Street Prescription

Much like a script written by a medical professional. A constant supply of drugs from a 'street pharmacist' aka a drug dealer.

Or

An addiction.

Subject 1: "Where you findin' all this valium?"

Subject 2: "When my pain pills for my back ran out I was forced to acquire a street prescription."

Subject 1: "That nigga Tyrone be fiendin' on those skittles."

Subject 2: "He gotta street prescription!"