Clinical Decision Support Systems (CDSS) are recently implemented in hospital settings to improve the reliability of drug ordering. However, such systems have limited effects due to their tendency to overalert. To healthcare professionals consider alerts, it is necessary to adapt the CDSS to their activity. Thus, it is necessary to consider contextualisation aspects in the system design. In this article, we propose a taxonomy integrating contextualisation elements issued from an activity analysis to guide the design of a contextualised CDSS. This taxonomy has been developed within the framework of the European project PSIP (Patient Safety through Intelligent Procedures in medication) aiming to make easier the identification and the prevention of Adverse Drug Events.