Why can't you use diazepam (valium) for muscle relaxation?

You can: Valium, a benzodiazepine class drug, was one of the first effective muscle relaxants utilized. Unfortunately it is over-utilized. Better, less-sedating and less-addictive drugs are now available. Valium leads to dependence, depression and other mood disorders. It's effects are greatly increased when taking alcohol or opioids, such as vicodin (another over-utilized drug).