The present invention relates to compositions forming a low viscosity mixture of:i) a non-polymeric slow-release matrixii) at least one biocompatible, (preferably oxygen containing) organic solvent；iii) at least one peptide active agent； andiv) at least one lipid soluble acid.The invention further relates to methods of treatment comprising administration of such compositions, especially in treating diabetes, and to pre-filled administration devices and kits containing the formulations.
