A central fill pharmacy is one that fills prescriptions for retail pharmacies pursuant to a contractual agreement or common ownership. When a retail pharmacy receives a prescription and then sends it to a second pharmacy to prepare and deliver back to the first pharmacy for dispensing to the patient, the second pharmacy is engaging in a "central fill activity." Retail pharmacy conceived of central fill pharmacies in the late 1990s as a means to assist in handling increased volumes of prescriptions. A central fill pharmacy provides pharmacists with the opportunity to increase the efficiency of resources, frees pharmacists' time for patient care activities, reduces dispensing errors, and reduces a patient's wait time. Most state boards of pharmacy have enthusiastically embraced central fill pharmacies, and many states have enacted laws to enable such operations.

The DEA, however, did not originally recognize central fill pharmacies, and thus the central filling of controlled substance prescriptions was not legal. In order to rectify this situation, the DEA enacted final regulations in 2003 to allow the central filling of controlled substances (68 Fed. Reg. 37405, 21 C.F.R. parts 1300, 1304, 1305, and 1306). Pursuant to the final regulations, central fill pharmacies may be registered as pharmacies, as long as state law authorizes this activity. Any person wishing to register as a central fill pharmacy and dispense controlled substances must do so in the same manner as any pharmacy. A central fill pharmacy must be staffed by a licensed pharmacist and may fill both new and refill prescriptions. Any prescription dispensed by the central fill pharmacy must be transported to the retail pharmacy that initially received the prescription, which would then deliver it to the patient. The label of the dispensed drug must contain a unique identifier (i.e., the central fill pharmacy's DEA registration number), indicating that the prescription was filled at the central fill pharmacy (21 C.F.R. § 1306.24(b)). It cannot accept a prescription directly from a patient or individual practitioner or deliver a prescription directly to the patient or individual practitioner. Both the central fill pharmacy pharmacist and the pharmacist who ultimately dispenses the prescription to the patient are bound by the corresponding responsibility doctrine (21 C.F.R. § 1306.05(f)).

A central fill pharmacy must have a contractual arrangement with the retail pharmacies for which it provides services, keep a list of those pharmacies, and verify the DEA registration of those pharmacies (21 C.F.R. § 1304.05). A retail pharmacy similarly must keep a list of the central fill pharmacies with which it contracts and verify their DEA registration. The information at both pharmacies must be available to the DEA upon request.

A retail pharmacy may contract with a central fill pharmacy in another state, providing that both states allow this activity. A retail pharmacy may, as a coincidental activity, operate also as a central fill pharmacy without maintaining a separate registration, inventories, or records.

The retail pharmacy must write the words "CENTRAL FILL" on the original paper prescription (21 C.F.R. § 1306.15 and § 1306.27). The retail pharmacy may then transmit the prescription to the central fill pharmacy in two ways. First, the controlled substance prescription (including schedule II prescriptions) may be faxed. The retail pharmacy must maintain the original hard copy and the central fill pharmacy must maintain the faxed prescription. Second, the prescription information may be transmitted electronically. The DEA has determined that there appears little risk of diversion in this situation, and thus does not require specific security standards for transmission. Of course, both pharmacies must keep all records related to the prescriptions transmitted and comply with all federal and state patient confidentiality and recordkeeping requirements.