Abstract: This invention provides an interdigitation-fusion liposome comprising an arachidonic acid metabolite, a lipid bilayer comprising a lipid and an aqueous compartment comprising a release-inhibiting buffer. Preferred arachidonic acid metabolites are the prostaglandins, particularly PGE.sub.1. The liposomal formulations can be used to treat animals, particularly humans, for diseases, disorders or conditions which can be ameliorated by prostaglandins, e.g., cell activation/adhesion disorders and inflammatory disorders.