Historically, people of almost every culture have used chemical agents to induce sleep,
relieve stress, and allay anxiety. While alcohol is one of the oldest and most universal
agents used for these purposes, hundreds of substances have been developed that produce
central nervous system (CNS) depression. These drugs have been referred to as "downers,"
sedatives, hypnotics, minor tranquilizers, anxiolytics, and antianxiety medications. Unlike
most other classes of drugs of abuse, depressants, except for methaqualone, are rarely
produced in clandestine laboratories. Generally, legitimate pharmaceutical products are
diverted to the illicit market.
Although a number of depressants (i.e., chloral hydrate, glutethimide, meprobamate and
methaqualone) have been important players in the milieu of depressant use and abuse, two
major groups of depressants have dominated the licit and illicit market for nearly a century,
first barbiturates and now benzodiazepines.
Barbiturates were very popular in the first half of this century. In moderate amounts, these
drugs produce a state of intoxication that is remarkably similar to alcohol intoxication.
Symptoms include slurred speech, loss of motor coordination and impaired judgment.
Depending on the dose, frequency, and duration of use, one can rapidly develop tolerance,
physical dependence and psychological dependence on barbiturates. With the development
of tolerance, the margin of safety between the effective dose and the lethal dose becomes
very narrow. That is, in order to obtain the same level of intoxication, the tolerant abuser
may raise his or her dose to a level that can produce coma and death. Although many
individuals have taken barbiturates therapeutically without harm, concern about the
addiction potential of barbiturates and the ever-increasing numbers of fatalities associated
with them led to the development of alternative medications. Today, only about 20% of all
depressant prescriptions in the United States are for barbiturates.
Benzodiazepines were first marketed in the 1960s. Touted as much safer depressants with
far less addiction potential than barbiturates, these drugs today account for about 30% of
all prescriptions for controlled substances. It has only been recently that an awareness has
developed that benzodiazepines share many of the undesirable side effects of the
barbiturates. A number of toxic CNS effects are seen with chronic high dose
benzodiazepine therapy. These include headache, irritability, confusion, memory
impairment, depression, insomnia and tremor. The risk of developing over-sedation,
dizziness and confusion increases substantially with higher doses of benzodiazepines.
Prolonged use can lead to physical dependence even at recommended dosages. Unlike
barbiturates, large doses of benzodiazepines are rarely fatal unless combined with other
drugs or alcohol. Although primary abuse of benzodiazepines is well documented, abuse of
these drugs usually occurs as part of a pattern of multiple drug abuse. For example, heroin
or cocaine abusers will use benzodiazepines and other depressants to augment heir "high"
or alter the side effects associated with over-stimulation or narcotic withdrawal.
There are marked similarities among the withdrawal symptoms seen with all drugs
classified as depressants. In it mildest form, the withdrawal syndrome may produce
insomnia and anxiety, usually the same symptoms that initiated the drug use. With a greater
level of dependence, tremors and weakness are also present, and in its most severe form,
the withdrawal syndrome can cause seizures and delirium. Unlike the withdrawal syndrome
seen with most other drugs of abuse, withdrawal from depressants can be life-threatening.