Intracellular Pharmacokinetics of Antidiabetic Drugs: A Focused Narrative Review of Subcellular Distribution (2015–2025)

<b>Background/Objectives:</b> The efficacy of antidiabetic drugs is determined by intracellular target exposure rather than solely by plasma concentrations. This review synthesizes current evidence regarding subcellular drug distribution and its clinical significance. <b>Methods:</b> A structured review of the literature published between 2015 and 2025 identified 73 relevant studies. Data were categorized by drug class, factors influencing distribution, and analytical methodologies. <b>Results:</b> Drug distribution patterns differ by class. Biguanides accumulate in mitochondria, thiazolidinediones localize in cell nuclei, and GLP-1 agonists are found in endosomes. Variations in transporter genes, such as OCT1, influence the extent of drug delivery to these subcellular targets. <b>Conclusions:</b> Investigations into intracellular drug movement elucidate their mechanisms of action. However, standardized human studies are required before these findings can inform clinical practice or regulatory decisions.