Operations Research Techniques in Supply Chain Optimisation for Pharmaceutical Distribution in Oyo State

This study applies operations research techniques to supply chain optimisation for pharmaceutical distribution networks in Oyo State, South West Nigeria, addressing the persistent challenges of stockouts, wastage, and inefficient routing that characterise public sector pharmaceutical logistics in the state. The Oyo State Pharmaceutical Services Department, which manages the distribution of essential medicines to over 300 primary healthcare facilities across the state's 33 local government areas, represents the operational context for this study. The study formulates a vehicle routing problem with time windows to optimise the routing and scheduling of distribution vehicles operating from the central medical store in Ibadan to facility delivery points. The Clarke-Wright savings algorithm is applied as a constructive heuristic for initial route generation, and a tabu search metaheuristic is subsequently used to improve solution quality. A linear programming transportation model is also developed to determine optimal stock allocation from the central store to secondary distribution points under budget and fleet capacity constraints. Input data on facility locations, demand quantities, delivery time windows, and vehicle specifications are sourced from departmental logistics records. Results indicate that optimised routing reduces total distribution distance by approximately 22 percent and eliminates three previously recorded instances of delivery time window violations per distribution cycle. The study contributes a practical operations research framework applicable to pharmaceutical logistics management for PGD-level health systems professionals. Keywords: operations research, vehicle routing, pharmaceutical distribution, supply chain, Oyo State