Planning and scheduling in pharmaceutical supply chains

Planning and scheduling are the common but important problems in pharmaceutical supply chains. High product turnover is crucial to the continued economic survival and growth of a pharmaceutical company. An issue that relates to this and the one that a pharmaceutical plant repeatedly needs to resolve is whether it can or should undertake to produce a new intermediate or product, or should outsource some tasks to enable it to do so. To address the above, we present a multi-period, continuous-time, mixed-integer linear program (MILP) model that addresses this important problem for the pharmaceutical plant using multiple parallel production lines in campaign mode, and producing products with multiple intermediates. Here, the aim is to decide the optimal production levels of various intermediates (new and old) or the optimal outsourcing policy to maximize the overall gross profit for the plant, while considering in detail the sequencing and timing of campaigns and material inventories. To address the challenging problem of scheduling in multipurpose batch plants like pharmaceutical plants, we present a new, simpler, more efficient, and potentially tighter, MILP model using a continuous-time representation with synchronous slots and a novel idea of several balances (time, mass, resource, etc.). The model uses no big-M constraints, and is equally effective for both maximizing profit and minimizing makespan.

Author dc:creator

• ARUL SUNDARAMOORTHY

• pharmaceutical supply chain, planning, scheduling, new product introductions, outsourcing, MILP, continuous-time formulation