Central nervous system (CNS) depressants are a class of drugs that slow down brain activity and cause muscles to relax. They include benzodiazepines, barbiturates, alcohol, opioids, and some sleeping pills. They work by enhancing the effects of the inhibitory neurotransmitter GABA at GABAA receptors in the brain, resulting in sedative, hypnotic, anxiolytic, and muscle relaxant effects. While effective for treating conditions like anxiety and insomnia, long-term use can lead to tolerance, addiction, and withdrawal symptoms.

2.  DEFINITION:-
 A type of drug that slows down brain
activity, which causes the muscles to
relax and calms and soothes a person.
CNS depressants are used to treat
insomnia (trouble sleeping), anxiety,
panic attacks, and seizures. They may
also be used to relieve anxiety and
tension before surgery. Examples of
CNS depressants are benzodiazepines,
barbiturates, and certain sleep
medicines. CNS depressants are
sometimes called sedatives or
tranquilizers. Also called central
nervous system depressant.

3.  Drugs that are classified as CNS
depressants include:
 Alcohol
 Barbiturates
 Benzodiazepines
 Many sleeping pills
 Opioids

5.  Alcohol
 Alcohol is one of the most widely used drugs in the world. The degree to which the brain
is affected by this central nervous system depressant depends on how much, and how
fast, a person drinks. Due to the initial positive behavioral effects of alcohol, many
people don’t realize that the substance is a CNS depressant. For example, when
someone first begins to drink, he or she may feel less reserved and more relaxed
because of the chemical changes alcohol causes within the brain. However, the more
someone drinks, the more the brain is affected and the likelihood that a negative
emotional response will take over. Alcohol can actually increase anxiety and stress
rather than reduce it, and elicit other negative reactions such as anger, aggression, and
depression. Chronic alcohol use can also lead to dependence, addiction, and withdrawal
symptoms when attempting to stop usage of the drug.
 Barbiturates
 Barbiturates, or “downers,” are a type of CNS depressant that are prescribed to treat
anxiety, tension, and sleep disorders. Common barbiturates include Amytal, Luminal
(Phenobarbital), Mebaral, Nembutal, and Seconal. Barbiturates were previously regarded
as a generally safe depressant, but problems with abuse, addiction, and overdose
quickly became apparent after widespread prescription. These drugs can generate a
sense of euphoria and relaxation even when taken in small doses, which encourages
abuse in some. Barbiturates have also shown to have a dramatic impact on sleep
patterns, resulting in suppressed REM sleep. In response to particularly high abuse rates
from the 1950s to the 1970s, benzodiazepines, which are generally regarded as less
addictive and less likely to cause overdose, were developed and popularized. Because
the potential for addiction and overdose is so high, the drugs are no longer commonly
used to treat anxiety and sleep problems.

6.  Benzodiazepines
 Sometimes called “benzos,” benzodiazepines are central nervous system depressants
that are prescribed to treat anxiety, sleep disorders, convulsions, and other acute stress
reactions. Common benzos include Valium, Xanax, and Ativan. Benzodiazepines are
highly effective in treating anxiety and insomnia due to the sleep-inducing, sedative,
and muscle-relaxing properties. While considered safe for short-term treatment, long-
term or illicit use can lead to the development of a tolerance, addiction, and withdrawal
symptoms upon cessation or rapid reduction in use.
 Sleeping Pills
 This category of CNS depressants includes non-benzodiazepine sleep aids, or “z-drugs,” such
as Ambien, Sonata, and Lunesta. These drugs are designed to specifically treat insomnia and
other sleep disorders. These sleeping pills are chemically different from other central nervous
system depressants, and they work by stimulating the GABA neurotransmitter in a different
way. Unlike benzodiazepines, Z-drugs do not reduce anxiety. The drugs are thought to have
fewer side effects and risk of addiction compared to benzodiazepines; however, long-term use
can still result in dependence and addiction.
 Opioids
 Opioids are the most commonly prescribed pain medications in the United States and in much
of the world. Some opioids, such as methadone, are also used for other purposes such as
opioid addiction treatment. There are a number of different opioids, including legal
prescription medications such as codeine and hydrocodone, and illegal street drugs, such as
heroin.
 While opioids vary tremendously in strength, addictive potential, and other aspects, they tend
to be very chemically similar and typically have similar effects. While opioids are considered
extremely effective for treating pain, they are also some of the most addictive and dangerous
drugs in the world. Every year, opioid overdose takes the lives of tens of thousands of
Americans.

8.  MECHANISIM OF ACTION
 Benzodiazepines enhance the effect of the neurotransmitter gamma-aminobutyric acid
(GABA) at the GABAA receptor, resulting in sedative, hypnotic (sleep-inducing),
anxiolytic (anti-anxiety), anticonvulsant, and muscle relaxant properties. effects are
thought to result from a facilitation of the action of gamma aminobutyric acid (GABA),
an inhibitory neurotransmitter in the central nervous system.
 Mode of action: GABAA receptor
 Use: Anxiety, seizures, muscle spasms

10.  MECHANISIM OF ACTION
 Barbiturates act as positive allosteric modulators and, at higher doses, as agonists of
GABAA receptors.[18] GABA is the principal inhibitory neurotransmitter in the
mammalian central nervous system (CNS). Barbiturates bind to the GABAA receptor at
multiple homologous transmembrane pockets located at subunit interfaces,[19] which
are binding sites distinct from GABA itself and also distinct from the benzodiazepine
binding site. Like benzodiazepines, barbiturates potentiate the effect of GABA at this
receptor. In addition to this GABAergic effect, barbiturates also block AMPA and kainate
receptors, subtypes of ionotropic glutamate receptor. Glutamate is the principal
excitatory neurotransmitter in the mammalian CNS.