Phenoxymethylpenicillin (PMP) has been reversibly intercalated into a layered double 14 hydroxide, and the resulting composite exhibits effective anti-bacterial activity. Powder X-ray diffraction studies indicate that the PMP molecules are interdigitated between the inorganic layers, and under mild acidic media, the molecules are released gradually. Therefore a sustained-release anti-bacterial medication is envisioned on the basis of this inorganic-drug composite. (c) 2005 Society of Chemical Industry.