Liposomes and lipid carriers in the treatment of microbial infections.

Since antibiotic treatment of severe infections is not always successful, intensification of the antibiotic treatment is needed. Targeting of antibiotics to infected tissues or cells by encapsulation in liposomes is under investigation and may be of importance in the treatment of infections that prove refractory to conventional forms of antibiotic therapy. In animal models of intracellular infections involving the mononuclear phagocyte system--parasitic, fungal, bacterial and viral infections--an improved therapeutic index and reduced toxicity resulting from encapsulation of the antibiotics in liposomes have been demonstrated. By varying the lipid composition of the liposomes it is possible to manipulate their intracellular degradation and thereby the intracellular release and therapeutic availability of the antibiotic. Efficacy of liposome-encapsulated antibiotics in the treatment of infectious diseases outside the mononuclear phagocyte system may be realized by manipulation of the liposome composition. Evidence for this is found in the treatment of systemic fungal infections, in which liposome appear to be very effective as a carrier of amphotericin B. The most advanced application of liposome-based therapy is in this field, and clinical studies with liposome-encapsulated amphotericin B have been in progress for several years.