Mathematical programming methods for reducing inequity due to stock-outs of pharmaceuticals in low-resourced regions using a mobile pharmacy

Delivering essential pharmaceuticals to consumers in low- and middle-income countries (LMICs) is a complex global challenge that requires equitable solutions in the last mile of pharmaceutical supply chains. This paper proposes using a mobile pharmacy to alleviate the burden due to pharmaceutical stock-outs among rural communities from an equity lens. The Stock-out Severity Index (SSI) is used to assess inequity and is used as the equity objective in a mobile facility routing model. We develop two mathematical programming approaches for routing of the mobile pharmacy so as to minimize the mean absolute deviation of the SSI. The first is a mixed integer program (MIP) modeling approach, based on an approximation of the SSI. The second is an implicit enumeration approach that is implemented within a chronological decomposition heuristic. To help establish its applicability potential, the paper describes a case study that demonstrates how a mobile pharmacy can effectively reduce inequity in a section of rural Uganda. In the case study, costs associated with improving equity are evaluated. This paper finds that optimizing for equity only is associated with high operational costs, and demonstrates approaches that achieve equitable solutions though constrained cost increases.