A system for constructing formularies is disclosed. The system includes a central computer system and at least one additional computer. The central computer system compiles a list of various pharmaceutical products and sorts them into different categories based on predetermined relational characteristics. The relational characteristics are based on therapeutic classifications of the pharmaceutical products, which in turn share these relational characteristics. Formularies are then created by selecting individual products and/or categories of products that the formularies would support. When prescription claims are received, coverage is either accepted or denied based on whether the products in die prescription claims are covered by the formulary.