CNS Depressants:Sedative-Hypnotics

Chapter 6

Introduction to CNS Depressants

• Why are CNS depressants problematic?- Usually prescribed under physician direction- Can cause very alarming and dangerous

behavior if not closely monitored• Most problems associated with these drugs

due to inadequate professional supervision

Introduction to CNS Depressants (continued)

• Why are CNS depressants problematic? - Seemingly unrelated drug groups can cause

CNS depression- Combination use can cause dangerous drug

interactions- Can cause disruptive personality changes

The History of CNS Depressants

• Attempts to find CNS depressants other than alcohol began in the 1800s.

• Bromides were introduced to treat nervousness and anxiety in the 1800s.- Very popular but toxic.

• In the early 1900s, bromides were replaced by barbiturates.- Initially heralded as safe and effective.- Problems with tolerance, dependence, and

safety became apparent.

The History of CNS Depressants (continued)

• In the 1950s the first benzodiazepines were marketed as substitutes for barbiturates.- Relatively safe when used for short periods- Long-term use can cause dependence and

withdrawal problems

The History of CNS Depressants (continued)

• Benzodiazepines were routinely prescribed for stress, anxiety, or apprehension.- In 1973 100 million prescriptions were written

for benzodiazepines.- Twice as many women as men taking them.- “Mother’s Little Helper” by the Rolling Stones.

• As medical community became aware of the problem, use of depressants declined.

The Effects of CNS Depressants

• CNS depressants reduce CNS activity and diminish the brain’s level of awareness.

• Depressant drugs include:- Benzodiazepines- Barbiturate-like drugs- Alcohol- Antihistamines- Opioid narcotics like heroin

The Effects of CNS Depressants (continued)

• Depressants are usually classified according to the degree of their medical effects on the body. For example:- Sedatives cause mild depression and relaxation

• Anxiolytic—drugs that relieve anxiety- Hypnotics induce drowsiness and encourage

sleep• Amnesiac effects can cause the loss of

memory

The Effects of CNS Depressants (continued)

• The same drug can cause different effects based on dose.- Low dose (sedatives—relieve anxiety and

promote relaxation)- Higher doses (hypnotics—can cause

drowsiness and promote sleep)- Even higher doses (anesthetics—can cause

anesthesia and are used for patient management during surgery)

Types of CNS Depressants

Benzodiazepines: Valium-Type Drugs- Prescribed for anxiety and sleep

• Medical uses- Relief from anxiety, treatment of neurosis,

relaxation of muscles, alleviation of lower-back pain, treatment of convulsive disorders, induction of sleep, relief from withdrawal symptoms, induction of amnesia

Types of CNS Depressants(continued)

• Mechanisms of action for benzodiazepine- Affect neurons that have receptors for the

neurotransmitter GABA

• GABA—inhibitory transmitter in brain regions- Limbic system (alter mood)- RAS (cause drowsiness)- Motor cortex (relax muscles)

Types of CNS Depressants (continued)

• Types of benzodiazepines- Many benzodiazepine compounds available in

the U.S.- Distinguished primarily by their duration of

action: short-acting (hypnotics), long-acting (sedatives)

• Side effects- Drowsiness to paradoxical effects - Tolerance, dependence, withdrawal, and abuse

Types of CNS Depressants (continued)

• Barbiturates played an important role as sedative-hypnotic agents.

• However, due to their narrow margin of safety and their abuse liability, they were replaced by benzodiazepines.- Caused many negative side effects, from nausea

to death, from respiratory or cardiovascular depression

Other Types of CNS Depressants

• Drugs with barbiturate-like properties- Chloral hydrate- Glutethimide- Methyprylon- Methaqualone

• Antihistamines

• GHB (gamma hydroxybutyrate)

Patterns of Abuse with CNS Depressants

• The American Psychiatric Association considers dependence on CNS depressants a psychiatric disorder.

Patterns of Abuse with CNS Depressants (continued)

• People most likely to abuse CNS depressants include individuals who - Use drugs to relieve continual stress- Paradoxically feel euphoria and stimulation

from depressants- Use depressants to counteract the unpleasant

effects of other drugs of abuse- Combine depressants with alcohol and heroin

to potentiate the effects

Patterns of Abusewith CNS Depressants (continued)

• Detoxification—the elimination of a toxic substance, such as a drug, and its effects- With CNS depressants, this is achieved by

substituting a longer-acting barbiturate for the offending CNS depressant and gradually reducing the dose.