Physics-based drug delivery modelling to predict and optimise the transport, release, and absorption of therapeutic agents in biological tissues. This work integrates diffusion, convection, and tissue–device interaction with mechanical deformation to capture realistic in vivo conditions. These models support the design of transdermal, mucosal, and implantable delivery systems by linking material properties, device geometry, and physiological parameters to drug concentration profiles. Such an approach enables rational optimisation of delivery efficiency, dosing accuracy, and clinical performance while reducing reliance on extensive experimental testing.