The present invention relates to a therapeutic agent formulation in the form of a nano-emulsion, comprising a continuous aqueous phase and at least one dispersed oily phase, in which the oily phase comprises further to the therapeutic agent, at least one amphiphilic lipid and at least one solubilising lipid, and in which the aqueous phase comprises at least one polyalkoxylated cosurfactant. The invention also relates to a preparation method and use of this formulation.