ABSTRACT
The applicability of liposomes in the treatment of infections is dependent on the pattern of biodistribution after intravenous administration, and the possibility of manipulating this in order to target the liposomes selectively. After intravenous administration, "classical" liposomes composed primarily of natural phospholipids and cholesterol are unable to leave the general circulation, and rapidly accumulate in cells of the mononuclear phagocyte system (MPS), particularly those in the liver and spleen. The role of these classical liposomes regarding treatment of infectious diseases may be twofold: first, a role for targeting of macrophage modulators to stimulate the cells of the MPS in infections in general (this aspect of enhancing the host defense will not be discussed further here); second, a role as carriers of antibiotic for treatment of infections in MPS tissues. The use of liposomes for delivery of antibiotic to infections in non-MPS tissues requires a reduced uptake by the MPS, enabling the liposomes to circulate long enough to reach the infected tissues or cells. The recent development of liposome formulations with long circulation half-lives opens new therapeutic avenues for improved delivery of antibiotics in infections in general, including infections in non-MPS tissues.
