The present invention relates to compositions forming a low viscosity mixture of: a. at least one diacyl glycerol and/or at least one tocopherol b. at least one phospholipid component comprising phospholipids having i. polar head groups comprising more than 50% phosphatidyl ethanolamine, and ii. two acyl chains each independently having 16 to 20 carbons wherein at least one acyl chain has at least one unsaturation in the carbon chain, and there are no more than four unsaturations over two carbon chains c. at least one biocompatible, oxygen containing, low viscosity organic solvent wherein optionally 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 non-lamellar liquid crystalline phase structure upon contact with an aqueous fluid. The invention further relates to methods of treatment comprising administration of such compositions, and to pre-filled administration devices and kits containing the formulations.
