Development of a computerized system for inventory of controlled drug substances

An automated drug inventory system was developed to facilitate record keeping requirements for controlled drug substances. A hand-held barcode scanner and a computer-accessible top-loading electronic balance are used to identify and weigh samples each time they are removed from or returned to the safe. A computer compares the initial sample weight to its last recorded weight to assure that no discrepancies occurred prior to sample use. Upon return, the computer compares the difference in initial and return tare weights to the stated amount of drug used to assure accuracy of the written inventory record. Unreconciled errors are immediately brought to the attention of the safe custodian. During its first year of operation, 2791 sample out/sample return transactions on 381 drug samples were tracked by the system. The most common errors detected by the system include sample loss of moisture (9), sample absorption of moisture (4), wrong sample used (4), incorrect weight recorded (4), and sample used without log entry (4). Importantly, all errors were immediately identified and reconciled. At the end of each working day, a printout of all daily transactions shows sample use, possible errors, and whether all samples have been returned to the safe. A printout of the total drug inventory is immediately available when called for. This system provides enhanced vigilance and security, and has been readily accepted by all investigators using controlled drug substances in our laboratory.