Toxicity screening of liposomes.

Phospholipids are the major components of most liposomes. Extensive testing of these naturally occurring compounds has revealed them to be remarkably safe for pharmaceutical use. Addition of other constituents to liposomes in order to alter stability or kinetics can result in an increase in toxic potential, particularly on parenteral administration of liposomes. This paper describes some simple in vitro cellular tests for direct toxicity of liposomes, particularly following intravenous (i.v.) or topical administration, including tests for haemolysis, thrombosis and cytotoxicity. In addition, an in vivo test for the effects on phagocytosis and for pyrogenicity are described, together with a brief outline of the requirements for the further toxicity testing of liposomal drugs at a later stage of development.