Medication planogram design to minimize collation delays and makespan in parallel pharmaceutical automatic dispensing machines

This paper presents an optimization study of the medication planogram design of parallel pharmaceutical automatic dispensing (PPAD) machines. The PPAD machines are widely used in central fill pharmacies to improve the prescription dispensing speed and accuracy nowadays. The objectives of this medication planogram design are to minimize the collation delay and makespan, which are evaluated along with the prescription scheduling problem. The planogram design has two levels: (1) the medication-dispenser assignment within the machine, which determines the dispensing speed and (2) the medication-machine assignment, which affects the collation delay (CD) for prescription orders. The integrated and hierarchical approaches are proposed to optimize the short-term and long-term medication planogram design, respectively. For the short-term planogram design, an integrated mathematical model and a two-link non-dominated genetic algorithm II (TL-NSGA-II) are proposed to solve the planogram design and order scheduling problems simultaneously. For the long-term planogram design, the planogram design is optimized based on the given support of medications sets, and then a tabu search non-dominated genetic algorithm II (TS-NSGA-II) is applied to solve this problem hierarchically. Thirty random samples are generated to test the proposed algorithms’ efficiency. Compared to the industrial package (the longest processing time heuristic), the proposed approaches can reduce collation delays and makespan significantly. The short-term planogram design, which optimizes the planogram design and order scheduling problems simultaneously, is more efficient if the planogram reset cost is trivial, compared to the long-term planogram design.