Epsilon Constraint Method to Solve the Routing-Inventory Problem of Refrigerated and Non-Refrigerated Drugs With Discount in Green Supply Chain

Supply Chain is a network of facilities and distribution centers that performs operation of preparation, conversion of raw materials into products and distribution of the final product to the customer. Recent technological, organizational and economic advances in comprehensive health systems have provided patients with more access to treatment. Despite this progress, improvements in health infrastructure and supply chain management are inevitable. Therefore, proper use of appropriate drugs with the right combination for the right patient at the right amount at the right time is essential for the safety and recovery of the disease. Therefore, in this paper, a drug supply chain network with considering discount on the green supply chain, including a pharmacy, a distribution center and a recycling center with a number of drugstores is studied, consisting of two homogeneous vehicle routing sections. A distribution center for medicines and a recycling center for pharmaceutical waste are set up. This research is solved by using the Epsilon constraint method with software of GAMs and after sensitivity analysis it is determined that the most important parameters are demand and then lost unit cost and unit hold cost. In other words, GAMs can solve this model for up to 5 nodes and 11 periods.