A drug delivery system for the controlled release of a pharmaceutically-active compound by oral route comprises an intercalate of a layered double hydroxide having, before intercalation, layers of metal hydroxides, and having intercalated therein a pharmaceutically-active compound having at least one anionic group. A preferred layered double hydroxide is one that has layers which comprise [LiAl2(OH)6]+. The drug delivery system has use in the delivery of drugs such as 4-biphenylacetic acid, Diclofenac, Gemfibrozil, Ibuprofen, Naproxen, 2-Propylpentanoic acid and Tolfenamic acid.