A pharmaceutical composition comprising a mixture of: (c) an active macromolecular principle; (d) an aromatic alcohol absorption enhancer chosen from propyl gallate, butylated hydroxy toluene (BHT), butylated hydroxy anisole (BHA) and analogs and derivatives thereof, or mixtures thereof; and (d) a biguanide or a pharmaceutically acceptable salt thereof, capable of increasing the solubility of the aromatic alcohol absorption enhancer in an aqueous medium, wherein the aromatic alcohol absorption enhancer is present in an amount by weight greater than or equal to that of the active principle.