Barbiturates are central nervous system (CNS) DEPRESSANTS ("downers"). These drugs produce sedative, hypnotic, and anesthetic effects. Depending on the dose used, any single drug in this class may produce sedation (decreased responsiveness), hypnosis (sleep), and anesthesia (loss of sensation). A small dose will produce sedation and relieve ANXI-ETY and tension; a somewhat larger dose taken in a quiet setting will usually produce sleep; an even larger dose will produce unconsciousness. The sleep produced by barbiturates, however, is not identical with normal sleep. Normal sleep consists of alternating phases of slow-wave sleep (SWS)—when the electroencephalogram (EEG) shows a high-voltage and low-frequency pattern—and rapid-eye-movement (REM) sleep. In the REM sleep phase, the EEG shows an arousal pattern and skeletal muscles relax, eyes move rapidly and frequently, and dreaming is thought to take place. Barbiturates decrease REM (or dreaming) sleep and thereby disturb the balance between SWS...