Barbiturates are a group of drugs that act as depressants on the central nervous system (the brain and spinal cord). They are derived from barbituric acid, a chemical discovered in 1863. Scientists looking for a drug to treat anxiety and nervousness that would not produce dependence (as do codeine and morphine) changed the structure of barbituric acid and synthesized barbital. Barbital, a depressant, was introduced as a medicine in 1903, followed by phenobarbital in 1913.

Since that time, more than 2,000 similar chemicals have been synthesized, but only about 50 of these have been sold as medicines. As more people took the drugs, the side effects of barbiturates became apparent. An overdose can result in respiratory depression (slowing or stopping normal breathing processes), which can be fatal. Doctors also realized that the barbiturates can be abused. People can become dependent on them, and a serious withdrawal syndrome can occur when a person abruptly...