INTRODUCTION: Delivering drugs to the central nervous system (CNS) remains a major challenge due to the blood-brain barrier, restricting the entry of drugs into the brain. This limitation contributes to the ongoing lack of effective treatments for CNS diseases. To improve the process of drug discovery and development, it is crucial to streamline methods that measure clinically relevant parameters, allowing for good selection of drug candidates. AREA COVERED: In this paper, we discuss the essential prerequisites for successful CNS drug delivery and review relevant methods. We emphasize the need for closer collaboration between in vitro and in vivo scientists to improve the relevance of these methods and increase the success rate of developing effective CNS therapies. While our focus is on small molecule drugs, we also touch on some aspects of larger molecules. EXPERT OPINION: Significant progress has been made in recent years in method development and their application. However, there is still work to be done before the use of in silico models, in vitro cell systems, and AI can consistently offer meaningful correlations and relationships to clinical data. This gap is partly due to limited patient data, but a lot can be achieved through in vivo research in animal models.