Sedative-hypnotic drugs — commonly called "depressants" — slow down or "depress" the activity of the brain. The best known are barbiturates (Amytal, Nembutal, Seconal, phenobarbital) and benzodiazepines (Ativan, Halcion, Librium, Valium, Xanax, Rohypnol). Other drugs in this group include chloral hydrate (which when mixed with alcohol was once known as "knockout drops" or a "Mickey Finn"), glutethimide (Doriden), methaqualone (Quaalude, Sopor, "ludes") and meprobamate (Equanil, Miltown and other brand names).
Although alcohol is also a depressant, alcohol is so common that health experts classify alcohol-related problems separately.
Regular use of these drugs often leads to "drug tolerance." That is, the body adjusts to them and it takes a higher and higher dose to achieve the desired effect. Dependence also can develop, meaning withdrawal symptoms will occur if the drug is suddenly stopped.
Many of these sedative-hypnotic drugs have legitimate uses. Benzodiazepines are a good treatment for anxiety and are also useful in sleep disorders. Barbiturates are used to treat seizures and for anesthesia during major surgery.
But using barbiturates to get "high" can be very dangerous. There is a relatively small difference between the desired dose and an overdose. A small miscalculation, which is easy to make, can lead to coma, respiratory distress (breathing slows or stops) and death. Withdrawal from barbiturates is similar to, and sometimes more severe than, alcohol withdrawal. Seizures are possible and can also lead to death.
Compared to barbiturates, benzodiazepines are much safer. They cause sedation but rarely stop a person's breathing or lead to death. They have the potential to be psychologically harmful by causing over-sedation, memory impairment, poor motor coordination and confusion. Withdrawal reactions can be extremely uncomfortable, although they usually are not deadly.
Combining any of these drugs, or using them with alcohol, can lead to dangerous effects. People often take these combinations to try to get higher or to counter unpleasant effects of other street drugs.