Liposomes are spherical vesicles composed of lipid bilayers that encapsulate drugs, and they significantly alter pharmacokinetics by changing absorption, distribution, metabolism, and excretion. The discovery of liposomes traces to Alec D. Bangham at the Babraham Institute and later work by lipid formulation experts such as Pieter R. Cullis at the University of British Columbia has refined clinical applications. Clinical regulatory milestones such as approval of pegylated liposomal doxorubicin Doxil by the U.S. Food and Drug Administration demonstrate real-world pharmacokinetic benefits and safety tradeoffs.
Mechanisms that change drug behavior
The primary causes of altered pharmacokinetics are encapsulation within the aqueous core or lipid bilayer and modification of the particle surface. Encapsulation protects labile molecules from immediate enzymatic degradation and renal filtration, producing a longer apparent half-life and higher systemic exposure. Surface modification by PEGylation reduces recognition by the reticuloendothelial system, lowering clearance by phagocytic cells in liver and spleen and extending circulation time. Size, charge, and lipid composition determine whether particles are rapidly sequestered or remain circulating. The enhanced permeability and retention effect described by H. Matsumura and Y. Maeda at Tohoku University explains preferential accumulation of suitably sized liposomes in many solid tumors, altering tissue distribution and increasing drug concentration at target sites while sparing normal tissues.
Consequences for efficacy, safety, and access
Clinically, these mechanistic changes often lead to improved therapeutic indices through higher target accumulation and reduced off-target toxicity. For example, pegylated liposomal formulations can lower rates of cardiotoxicity or gastrointestinal toxicity compared with free drug, a consequence documented during regulatory review by the U.S. Food and Drug Administration. However, longer circulation is not universally beneficial; altered distribution can create new toxicities related to skin or infusion reactions and may require different dosing schedules.
Beyond biology, there are human and territorial nuances. Manufacturing complexity and cold-chain handling raise costs and concentrate production capacity in higher-resource regions, which affects global access and equity. Environmental considerations include sourcing of lipids and solvent use during production, prompting sustainability efforts in pharmaceutical manufacturing. From an evidence perspective, foundational work by Alec D. Bangham at the Babraham Institute and translational advances by Pieter R. Cullis at the University of British Columbia, together with clinical experience documented by regulatory bodies, underpin current understanding of how liposomal formulations reshape drug pharmacokinetics.