Fenobam hydrate is a selective and orally active mGluR5 antagonist ( IC 50 =84 nM) that can penetrate the blood-brain barrier. Fenobam hydrate shows the K d values of 54 nM and 31 nM on rat and human recombinant mGlu5 receptors, respectively. Fenobam hydrate has anxiolytic activity, inhibits self-administration behavior in rat, and induces apoptosis in cancer cells. Fenobam hydrate can be used for research on neurological diseases, cancer and drug addiction.