Interface for iontophoresis

1. Field of the Invention A hydrophilic membrane having a low adsorptivity for a protein is disposed, as an interface, on a side to be contacted with a skin, and a drug such as a physiologically active peptide is transdermally delivered by iontophoresis. The membrane has an adsorptivity for a protein of not greater than 10 g/cm. The thickness of the membrane is about 10 to 200 m, and the porosity of the membrane is about 60 to 90%. Such membrane includes a hydrophilized fluororesin membrane, a hydrophilized polysulfone membrane and a hydrophilized cellulose derivative membrane.