The present invention relates to pre-formulations comprising low viscosity, non-liquid crystalline, mixtures of:a) at least one neutral diacyl lipid and/or at least one tocopherol；b) at least one phospholipid；c) at least one biocompatible, oxygen containing, low viscosity organic solvent；wherein at least one bioactive agent is dissolved or dispersed in the low viscosity mixture and wherein the pre-formulation forms, or is capable of forming, at least one liquid crystalline phase structure upon contact with an aqueous fluid. The preformulations are suitable for generating parenteral, non-parenteral and topical depot compositions for sustained release of active agents. The invention additionally relates to a method of delivery of an active agent comprising administration of a preformulation of the invention, a method of treatment comprising administration of a preformulation of the invention and the use of a preformulation of the invention in a method for the manufacture of a medicament.
