An effective surveillance program of drugs and addiction requires timely detection of emerging consumption patterns and new psychoactive substances. The time lag between conventional reporting systems and population-level perception creates a gap that can be more effectively addressed through sentinel networks.To advance the development of a drug-use sentinel network in Spain by building on our previously published study, focusing specifically on operational structure, implementation strategies, and the integration of digital tools and new technologies to enhance real-time surveillance.A qualitative study was conducted between February and May 2025. A total of 13 regional, national and international experts in public health, drug policy, prevention, epidemiology, and digital technologies participated in three focus groups and four in-depth interviews. Data were analyzed thematically using ATLAS.ti, with triangulation of researcher data with adherence to SRQR guidelines to ensure rigor.Six categories and 16 subcategories were identified for the design of a sentinel network on drug use: (1) Definition and criteria for activating sentinel alerts; (2) Selection of key informants; (3) Communication of relevant signals and alerts; (4) Management and temporality of alerts; (5) National coordination of the sentinel network; and (6) Enabling factors for sustainability.The categories identified in the study reflect the complexity of designing a functional sentinel network for monitoring drug use. The definition of alert criteria and the selection of key informants highlight the need for clarity and consistency to ensure reliable early detection. Effective communication pathways and clear temporal management of alerts are essential to prevent delays and reduce variability between settings. The emphasis on national coordination demonstrates the importance of a unified structure capable of integrating heterogeneous local contributions. Finally, the enabling factors identified—such as training, digital tools, and mechanisms to maintain engagement—underscore that sustainability depends not only on design, but on long-term operational support.This work outlines the operational foundations for an effective drug-use sentinel system, emphasising clear alert management, robust coordination and digital support. Implementing these elements could improve real-time detection capacity and reinforce national surveillance infrastructures.