The invention provides the use of a compound capable of preferential interaction with plasma membrane lipid microdomains (PMLMs) as enhancers of transport processes across endothelial, epithelial and mesothelial membranes (ie including blood-brain-blood barrier and gastrointestinal mucosal membranes). When associated with therapeutic agents, the compounds act as transport vehicles. When the compounds interact with PMLMs in such a way as to inhibit transport across the membrane, the compounds function as anti-infective agents.