Over the past 50 years, the problem of sedative addiction (physical and psychological dependence) shifted from being almost completely an abuse of short- or intermediate-acting barbiturates (e.g., amobarbital, pentobarbital, secobarbital) to being an abuse of newer hypnotics (glutethimide, methaqualone) and, most recently, benzodiazepines (e.g., diazepam, alprazolam). All these agents (and alcohol) produce cross-tolerance—that is, physical withdrawal symptoms in a patient who is dependent on any one of these drugs can be relieved by an adequate dose of another. The time course of withdrawal symptoms differs with the half-lives of the drugs involved, beginning within 12–16 hours after the last dose of a short-acting agent (e.g., amobarbital, alprazolam) and perhaps 2–5 days after the last dose of diazepam.