Ocular microdialysis in preclinical pharmacokinetic studies: Principles, challenges, and practical insights

Accurate characterization of ocular pharmacokinetics (PK) is essential for understanding drug absorption, distribution, metabolism, and elimination following ophthalmic administration. However, reliable assessment of intraocular drug exposure remains challenging because plasma concentration poorly reflects ocular drug levels and traditional PK studies rely on terminal tissue sampling that are labor-intensive, require a large number of animals, and produce total drug concentrations at limited time points. Microdialysis is an in vivo sampling technique that enables continuous measurement of unbound drug concentrations directly in the extracellular fluid of living tissues, providing PK profiles of the pharmacologically active fraction. Although microdialysis has been widely applied in neuroscience and peripheral tissues, its implementation in ocular PK studies presents unique challenges due to the eye's compartmentalized anatomy and special fluid dynamics. This review provides a comprehensive evaluation of microdialysis methodology with an emphasis on ocular PK applications, summarizing the principles of microdialysis, technological developments in probe design and membrane materials, and commonly used recovery calibration strategies. A systematic analysis of published ocular microdialysis studies is presented to identify current practices and methodological gaps, including variability in recovery estimation approaches, species selection, and experimental conditions. To contextualize these considerations, a case study investigating the ocular PK of the prostaglandin analog prodrug latanoprost is presented. Experimental results highlight the impact of temporal lag and recovery calibration on ocular PK interpretation and demonstrate that microdialysis-derived exposure profiles can closely recapitulate human ocular PK under comparable conditions. Finally, best-practice recommendations are proposed to help guide experimental design, recovery estimation, data interpretation, and translational relevance of future ocular microdialysis studies.