CNS Depressants

Central Nervous System
Depressants

Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

CNS Depressants

Sedatives
• Drugs that have an inhibitory effect on the
CNS to the degree that they reduce:
– Nervousness
– Excitability
– Irritability
– without causing sleep


CNS Depressants

Hypnotics
• Calm or soothe the CNS to the point that they
cause sleep


CNS Depressants

Sedative-Hypnotics—dose dependent:
• At low doses, calm or soothe the CNS
without inducing sleep
• At high doses, calm or soothe the CNS
• to the point of causing sleep


Sedative-Hypnotics: Barbiturates

• First introduced in 1903, standard agents
for insomnia and sedation
• Habit-forming
• Only a handful commonly used today due
in part to the safety and efficacy of:
BENZODIAZEPINES


Four categories:
• Ultrashort
– mephobexital, thiamylal, thiopental
• Short
– pentobarbital, secobarbital
• Intermediate
– aprobarbital, butabarbital
• Long
– phenobarbital


Barbiturates have a very narrow therapeutic index.

Therapeutic Index
• Dosage range within which the drug is effective
but above which is rapidly toxic.



Mechanism of Action
• Site of action:
– Brain stem (reticular formation)
– Cerebral cortex
• By inhibiting GABA, nerve impulses traveling in
the cerebral cortex are also inhibited.



Drug Effects
• Low doses: Sedative effects

• High doses: Hypnotic effects
(also lowers respiratory rate)

Notorious enzyme inducers



Therapeutic Uses
• Hypnotics
• Sedatives
• Anticonvulsants
• Surgical procedures



Side Effects
Body System Effects
CNS Drowsiness, lethargy, vertigo
mental depression, coma

Respiratory Respiratory depression, apnea,
bronchospasms, cough



Side Effects
Body System Effects
GI Nausea, vomiting, diarrhea

Other Agranulocytosis,
vasodilation, hypotension,
Stevens-Johnson syndrome



Toxicology
• Overdose frequently leads to respiratory depression,
and subsequently, respiratory arrest.
• Can be therapeutic:
– Anesthesia induction
– Uncontrollable seizures: “phenobarbital coma”


Drug Interactions
• Additive effects:
– ETOH, antihistamines, benzodiazepines,
narcotics, tranquilizers
• Inhibited metabolism:
– MAOIs will prolong effects of barbiturates
• Increased metabolism:
– Reduces anticoagulant response, leading to
possible clot formation

CNS Depressants: Benzodiazepines

Most frequently prescribed sedative-hypnotics
• Most commonly prescribed drug classes
• Favorable side effects
• Efficacy
• Safety



Classified as either:
• Sedative-hypnotic or Anxiolytic

(Medication that relieves anxiety)



Sedative-Hypnotic Type
• Long-Acting:
– flurazepam (Dalmane), quazepam (Doral)

• Short-Acting:
– estazolam (Prosom), temazepam (Restoril),
– triazolam (Halcion)


Anxiolytic Type
• alprazolam (Xanax)
• chloridiazepoxide (Librium)
• diazepam (Valium)
• lorazepam (Ativan)
• midazolam (Versed)

zolpidem (Ambien) and zaleplon (Sonata)
(nonbenzodiazepine hypnotic agents, share characteristics)



Mechanism of Action
• Depress CNS activity
• Affect hypothalamic, thalamic, and limbic
systems of the brain
• Benzodiazepine receptors



Drug Effects
• Calming effect on the CNS
• Useful in controlling agitation and anxiety


Therapeutic Uses
• Sedation
• Sleep induction
• Skeletal muscle relaxation
• Anxiety relief
• Treatment of alcohol withdrawal
• Agitation
• Depression
• Epilepsy
• Balanced anesthesia


Side Effects
• Mild and infrequent
Headache Drowsiness
Dizziness Vertigo
Lethargy
Paradoxical excitement (nervousness)
“Hangover effect”


CNS Depressants:
Nursing Implications
• Before beginning therapy, perform a
thorough history regarding allergies, use
of other medications,health history, and
medical history.
• Obtain baseline vital signs and I & O,
including supine and erect BPs.
• Assess for potential disorders or conditions
that may be contraindications, and for
potential drug interactions.

CNS Depressants:
• Give 15 to 30 minutes before bedtime for
maximum effectiveness in inducing sleep.
• Most benzodiazepines (except flurazepam)
cause REM rebound and a tired feeling the
next day; use with caution in the elderly.
• Patients should be instructed to avoid
alcohol and other CNS depressants.


CNS Depressants:
• Check with physician before taking any other
medications, including OTC medications.
• It may take 2 to 3 weeks to notice improved
sleep when taking barbiturates.
• Abruptly stopping these medications,
especially barbiturates, may cause rebound
insomnia.


CNS Depressants:
• Safety is important
– Keep side rails up
– Do not permit smoking
– Assist patient with ambulation
(especially the elderly)
– Keep call light within reach

• Monitor for side effects


CNS Depressants:
• Monitor for therapeutic effects
– Increased ability to sleep at night
– Fewer awakenings
– Shorter sleep induction time
– Few side effects, such as hangover effects
– Improved sense of well-being because of
improved sleep


CNS Depressants

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