Modelling and Optimisation of Production Scheduling in a Multi-Product Pharmaceutical Manufacturing Environment in Lagos State

This study develops a mathematical optimisation model for production scheduling in a multi-product pharmaceutical manufacturing environment in Lagos State, South West Nigeria, addressing the gap between theoretical scheduling research and the practical scheduling complexities of Nigerian pharmaceutical production contexts. Multi-product pharmaceutical manufacturing involves sequence-dependent setup times, regulatory-imposed batch segregation requirements, and dynamic demand from hospital procurement systems, creating a scheduling problem of significant complexity. This research formulates a mixed-integer linear programming model that minimises total weighted tardiness across a planning horizon of four weeks while satisfying batch segregation, equipment capacity, and workforce availability constraints. The model is developed using real production data from a Lagos-based pharmaceutical manufacturer, covering forty-two active product codes across three production lines. Due to computational complexity at industrial scale, a simulated annealing metaheuristic is implemented and benchmarked against the exact solution for problem instances of varying size. Results demonstrate that the metaheuristic achieves solutions within three-point-two percent of optimality for large instances while reducing computation time from hours to minutes. Implementation recommendations include integration of the scheduling model into the company's production planning workflow through a decision support interface. Keywords: production scheduling, mixed-integer linear programming, pharmaceutical manufacturing, simulated annealing, Lagos State