The present invention relates to topical bioadhesive 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 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.