Systematic Design and Evaluation of Nasal Drug Delivery for Central Nervous System Disease from Experimental to...

Disorders of the central nervous system (CNS) are intricate and often resistant conditions that create a significant global impact, affecting millions of individuals each year. The blood-brain barrier (BBB) acts as a protective mechanism for the brain against external substances, but it also prevents most therapeutic agents from entering the CNS, leading to inadequate drug absorption and reduced effectiveness after diagnosis. Nasal drug delivery has emerged as a viable approach to bypass the BBB, facilitating direct access to the brain through the olfactory and trigeminal nerve routes. Although considerable research focuses on innovative nasal formulations with proven clinical promise, a critical gap persists: a systematic framework that bridges laboratory breakthroughs with clinical implementation. This review addresses this unmet need by integrating recent basic research advances with practical clinical requirements. We summarize nasal transport pathways, targeted design strategies, formulation optimization, and device engineering. Crucially, we propose a structured clinical evaluation framework built upon five essential pillars: targeting precision, pharmacokinetic performance, multi-organ safety profiling, device-drug clinical compatibility, and anatomical translation from animal models to humans. By mapping current research capabilities against clinical readiness criteria, this framework identifies translational bottlenecks and provides actionable guidance to accelerate the bench-to-bedside transition of intranasal drug delivery systems for CNS disorders.