The use of conversational technologies to create conversational virtual patients (CVPs) holds great promise for improving the communication skills and medical knowledge of future physicians. This design science study aims to establish effective design principles for the implementation of CVPs. Based on existing literature and insights gained through semi-structured interviews with physicians, this study identifies design requirements and synthesizes them into four design principles: authentic representation, user adaptability, performance feedback, and user friendliness. The prototypical instantiation and first round of positive evaluation of a CVP for the symptom of stomach pain provides support for the validity of these principles. The study contributes actionable guidance for the development of future CVPs, ensuring that future medical education meets the evolving needs of digital-native learners.