en Mathematical Modeling and Applications of OR Mathematical Modeling and Applications of OR پژوهشی Original <span style="font-size:12pt"><span style="line-height:normal"><span new="" roman="" style="font-family:" times="">Facility location and routing problems have attracted significant research attention since the 1960s due to their practical relevance and complexity. Efficiently establishing production facilities, optimizing vehicle routes, and implementing effective inventory systems are essential for improving organizational performance. In this study, we propose an integrated location-routing model for the pharmaceutical supply chain, designed to satisfy all retailer demands through an appropriate inventory policy, ensuring no demand is unmet. The proposed mixed-integer mathematical model considers a four-tier supply chain, including manufacturers, distributors, wholesalers, and retailers, with the objective of establishing cost-effective warehouses while fulfilling all demand requirements. Demand uncertainty is addressed using a scenario-based probabilistic approach. The model is solved using GAMS for a small-scale case study. For larger-scale instances, where exact solutions are computationally challenging, a meta-heuristic approach&mdash;specifically, a genetic algorithm&mdash;is employed to efficiently obtain near-optimal solutions.</span></span></span><br> &nbsp; Demand uncertainty, Location routing problem, inventory system, Meta-heuristic algorithm, Pharmaceutical supply chain 32 59 http://iors.ir/journal/browse.php?a_code=A-10-6049-2&slc_lang=en&sid=1 Amir-Mohammad Golmohammadi a-golmohammadi@araku.ac.ir 00031947532846002993 00031947532846002993 Yes Associate Professor of Industrial Engineering, Arak University, Arak, Iran. Hamidreza Abedsoltan 00031947532846002994 00031947532846002994 No