This paper describes a Human Factors Engineering approach to a medication use system in a context of a hospital medication CPOE project. It presents the results obtained from the organizational analysis and describes the variations in distribution of tasks between the actors of the medication use process, depending on the organization of the work system. It then focuses on nurses’ medication administration tasks including the preparation and update of pills dispensers. This situation may be characterized according to the distributed cognition framework. The high level organizational features have an impact on the quality and safety of the coordination and communication procedures characterizing the nurses’ medication preparation and administration tasks.