Tissue inflammation reshapes the microenvironment in ways that change how drugs move, are taken up, and work at a local level. Inflammatory signals alter blood flow, vessel structure, extracellular space, and cellular behavior, producing consequences for both small-molecule drugs and advanced formulations such as nanoparticles. As shown by Rakesh K. Jain, Massachusetts General Hospital and Harvard Medical School, elevated interstitial fluid pressure and chaotic tumor vasculature can limit convective drug transport and reduce penetration into inflamed tissue, decreasing local efficacy.
Vascular and interstitial changes
Inflammation commonly increases vascular permeability, producing edema and widening endothelial gaps that change convective and diffusive transport. These changes can transiently increase delivery of some compounds but often reduce effective distribution by creating heterogeneous perfusion and pooling of fluids. Heterogeneity within the inflamed tissue means some regions receive excess drug while others are undertreated. In cancer and chronic inflammatory sites this is compounded by raised interstitial fluid pressure, which opposes inward fluid flow and hinders drugs from reaching target cells, a mechanism emphasized in work by Rakesh K. Jain, Massachusetts General Hospital and Harvard Medical School. In airways, chronic inflammation remodels structure and alters deposition patterns of inhaled agents, a clinical nuance highlighted by Peter J. Barnes, National Heart and Lung Institute Imperial College London.
Cellular and biochemical modulation
At the cellular level, cytokines such as interleukin-6 and tumor necrosis factor change expression of drug-metabolizing enzymes and transporters, altering local activation, inactivation, and efflux. E. T. Morgan, University of Washington, has documented how inflammatory signaling downregulates hepatic cytochrome P450 enzymes, illustrating a broader principle that inflammation shifts local biotransformation and therefore effective concentrations. Immune cells further modulate distribution: activated macrophages and neutrophils sequester particulates and nanoparticles, reducing availability to parenchymal targets and sometimes creating local reservoirs of toxicity, a behavior investigated in studies by Sangeeta N. Bhatia, Massachusetts Institute of Technology.
Consequences include reduced drug penetration, unpredictable therapeutic windows, and heightened local side effects where concentration becomes excessive. Clinically, this argues for measuring inflammatory biomarkers to guide dosing, using delivery systems that bypass sequestration, or combining therapy with anti-inflammatory strategies to normalize microvascular function. Context matters: geographic differences in infectious and inflammatory disease burden, cultural access to anti-inflammatory care, and environmental exposures such as pollution can all modulate how inflammation influences drug outcomes across populations.