In 1903, Hermann Emil Fischer and Joseph von Mering disclosed their discovery that diethylbarbituric acid, formed from the reaction of  acid, phosphorus oxychloride and urea, induces sleep in dogs. The discovery was patented and licensed to Bayer pharmaceuticals, which marketed the compound under the trade name Veronal as a sleep aid beginning in 1904. Systematic investigations of the effect of structural changes on potency and duration of action led to the discovery of phenobarbital at Bayer in 1911 and the discovery of its potent anti-epileptic activity in 1912.  Phenobarbital was among the most widely used drugs for the treatment of epilepsy through the 1970s, and as of 2014, remains on the World Health Organizations list of essential medications. The 1950s and 1960s saw increased awareness of the addictive properties and abuse potential of barbiturates and amphetamines and led to increasing restrictions on their use and growing government oversight of prescribers.  Today, amphetamine is largely restricted to use in the treatment of attention deficit disorder and phenobarbital in the treatment of epilepsy.
In 1958, Leo Sternbach discovered the first benzodiazepine, chlordiazepoxide (Librium). Dozens of other benzodiazepines have been developed and are in use, some of the more popular drugs being diazepam (Valium), alprazolam (Xanax), clonazepam (Klonopin), and lorazepam (Ativan). Due to their far superior safety and therapeutic properties, benzodiazepines have largely replaced the use of barbiturates in medicine, except in certain special cases. When it was later discovered that benzodiazepines, like barbiturates, significantly lose their effectiveness and can have serious side effects when taken long-term, Heather Ashton researched benzodiazepine dependence and developed a protocol to discontinue their use.