Predictors of drug bioavailability in chronic disease patients with targeted delivery limitations

Abstract

Oral bioavailability in chronic disease patients depends on an overlapping set of formulation, transporter-enzyme, and organ-function variables, and targeted drug delivery systems are increasingly used to work around this variability rather than eliminate it. This paper synthesizes the biopharmaceutics, pharmacokinetics, and nanomedicine literature to identify the predictors of variable bioavailability in chronic kidney disease, hepatic dysfunction, and obesity, and to characterize where liposomal, polymeric, and lipid-nanoparticle carrier systems reach their own disease-dependent limitations. Dissolution rate, intestinal P-glycoprotein and CYP3A4 activity, renal and hepatic clearance, and body composition each independently predict systemic exposure, while carrier-based delivery narrows but does not remove this variability because reticuloendothelial clearance, vascular permeability, and receptor expression are themselves altered by chronic disease. Individualizing therapy in chronic disease populations requires treating renal function, hepatic extraction ratio, body composition, and transporter-enzyme burden as an explicit predictor set for both conventional and targeted formulations, rather than assuming carrier-based delivery is immune to the physiology it was designed to work around.