Customized pharmaceutical products aim to comply with the individual needs of a patient to enhance the treatment outcome. The current pharmaceutical production paradigm is, however, dominated by mass production, where the pharmaceutical products embrace a one-size-fits-all design with a low possibility of treatment optimization to patient needs. This production paradigm is not designed or intended for customized pharmaceutical products and operating this production context for customized pharmaceutical products is argued to be cost-inefficient. To address this challenge of inefficient production of customized pharmaceutical products, this study proposes an approach to modular pharmaceutical product design. As a mass customization strategy, product modularization enables serving customers with customized products cost-efficiently. The proposed modular pharmaceutical products integrate three product design requirements originating from patient needs: a scalable dose strength, a flexible target release profile, and a scalable treatment size. An approach to assess the value of these product designs is presented, by means of proposing three benefit metrics complying with respective design requirements and a cost metric assessing the cost of producing these modular pharmaceutical product designs. Results suggest that pharmaceutical product modularization can, by keeping the number of produced components low, substantially increase the external product variety and, hence, enhance the treatment outcome of patients. Furthermore, results indicate that the achieved benefit for the patient through product modularization increases beyond additional costs arising during production. However, a careful modularization must be performed to optimize the tradeoff between the increased benefit and cost.