What is Diazepam? Diazepam, first marketed as Valium, is a medication of the benzodiazepine family that typically produces a calming effect. It is commonly used to treat a range of conditions including anxiety, alcohol withdrawal syndrome, benzodiazepine withdrawal syndrome, muscle spasms, seizures, trouble sleeping, and restless legs syndrome. It may also be used to cause memory loss during certain medical procedures. It can be taken by mouth, inserted into the rectum, injected into muscle, or injected into a vein. When given into a vein, effects begin in one to five minutes and last up to an hour. By mouth, effects may take 40 minutes to begin.