A pharmacy recently reported an incident in which a patient received a mixture of two controlled substances due to an error involving return-to-stock (RTS) medication vials. The prescription was for hydrocodone-acetaminophen, but during the filling process, a technician retrieved both a manufacturer’s bottle of hydrocodone-acetaminophen and an RTS bottle of oxycodone-acetaminophen. Both bottles’ contents were poured onto an Eyecon counting machine, which is designed to count and identify tablets using a camera. However, the visual similarity between the two medications led to the machine failing to detect that different drugs were present.
The technician finished dispensing and passed the prescription on for pharmacist verification. The pharmacist did not notice that the vial contained tablets from two different medications. The mixed medication was dispensed to the patient, who noticed differing tablets in the vial after beginning treatment and contacted the pharmacy. The pharmacy then corrected the mistake by providing the correct medication and set aside the oxycodone-acetaminophen tablets for disposal.
According to the report, several factors contributed to this event. The pharmacy’s system does not print RTS labels with usable barcodes; staff cover patient names with privacy labels when returning prescriptions to stock instead. Only the manufacturer's bottle was scanned during counting; no barcode scan was performed on the RTS vial. Manual verification steps failed, as neither technician nor pharmacist noticed that different medications were involved based on National Drug Code (NDC) checks or physical appearance—an issue compounded by similar tablet appearances and possible misplacement of RTS vials on shelves.
Due to repeated reports of errors related to return-to-stock processes and potential risks for patients, ISMP has published Best Practice 7: “Maximize the use of technology to prevent errors during the return-to-stock (RTS) process.” This recommendation calls for pharmacies and software vendors to implement measures such as generating specific RTS labels that include drug details and scannable barcodes, verifying barcodes throughout dispensing workflows, automating guidance on using available RTS medications before automated dispensing is triggered, and ensuring correct placement of labeled vials on shelves.
Additionally, following this incident, opportunities were identified by pharmacy staff to improve their perpetual inventory procedures for controlled substances. At present, quantities are documented electronically only after dispensing occurs; they are now exploring pre-dispensing inventory checks—particularly for medications returned to stock—to enhance accuracy and accountability.
Alerts Sign-up