pharmacology cns depressant

7/29/2019 pharmacology CNS depressant

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Central Nervous System

Depressants


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CNS Depressants

Sedatives

Drugs that have an inhibitory effect on theCNS to the degree that they reduce:

Nervousness

Excitability

Irritability

without causing sleep


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CNS Depressants

Hypnotics

Calm or soothe the CNS to the point that theycause sleep


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CNS Depressants

Sedative-Hypnoticsdose dependent:

At low doses, calm or soothe the CNSwithout inducing sleep

At high doses, calm or soothe the CNS

to the point of causing sleep


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Sedative-Hypnotics:

Barbiturates

First introduced in 1903, standard agentsfor insomnia and sedation

Habit-forming

Only a handful commonly used today duein part to the safety and efficacy of:BENZODIAZEPINES


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Sedative-Hypnotics:

Barbiturates

Four categories:

Ultrashort

mephobexital, thiamylal, thiopentalShort

pentobarbital, secobarbital

Intermediate

aprobarbital, butabarbital,amobarbital

Long

Phenobarbital,mephobarbital


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Sedative-Hypnotics:

Barbiturates

Barbiturates have a very narrow therapeuticindex.

Therapeutic IndexDosage range within which the drug is effectivebut above which is rapidly toxic.


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Sedative-Hypnotics:

Barbiturates

Mechanism of Action

Site of action:

Brain stem (reticular formation)

Cerebral cortex

By inhibiting GABA, nerve impulses traveling inthe cerebral cortex are also inhibited.


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Barbiturates and benzodiazepines actsimilarly to produce depression of centralnervous system function and behavior.

Both classes of drugs enhance the abilityof the inhibitory neurotransmitter,gamma aminobutyric acid (GABA), toactivate a type of receptors known as

GABA-A receptors. These drugs increasethe effectiveness of GABA by altering thereceptor so that GABA can bind more

easily, an effect known as allostericregulation. Activation of the GABA-Areceptor opens an ion channel, allowingnegatively charged chloride ions to enter

the cell, producing an inhibition of
http://www2.csusm.edu/DandB/GABA.htmlhttp://www2.csusm.edu/DandB/GABA.html


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GABA is the main inhibitory neurotransmitter

in the central nervous system (CNS)..


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Sedative-Hypnotics:

Barbiturates

Drug Effects

Low doses: Sedative effects

High doses: Hypnotic effects(also lowers respiratory rate)


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Sedative-Hypnotics:

Barbiturates

Therapeutic Uses

Hypnotics

Sedatives

Anticonvulsants

Surgical procedures


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Sedative-Hypnotics:

Barbiturates

Side Effects

Body System Effects

CNS Drowsiness, lethargy, vertigomental depression, coma

Respiratory Respiratory depression, apnea,

bronchospasms, cough


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Sedative-Hypnotics:

Barbiturates

Side Effects

Body System Effects

GI Nausea, vomiting, diarrhea

Other Agranulocytosis,vasodilation, hypotension,

Stevens-Johnson syndrome


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Sedative-Hypnotics:

Barbiturates

Toxicology

Overdose frequently leads to respiratorydepression, and subsequently,

respiratory arrest.Can be therapeutic:

Anesthesia induction

Uncontrollable seizures: phenobarbitalcoma


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Sedative-Hypnotics:

Barbiturates

Drug InteractionsAdditive effects:

antihistamines, benzodiazepines,

narcotics, tranquilizersInhibited metabolism:

MAOIs will prolong effects ofbarbiturates

Increased metabolism:

Reduces anticoagulant response,leading to possible clot formation


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CNS Depressants:

Benzodiazepines

Most frequently prescribed sedative-hypnotics

Most commonly prescribed drug classes

Favorable side effects

Efficacy

Safety


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CNS Depressants:

BenzodiazepinesClassified as either:Sedative-hypnotic or Anxiolytic

(Medication that relieves anxiety)


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CNS Depressants:

Benzodiazepines

Sedative-Hypnotic Type

Long-Acting:

flurazepam (Dalmane), quazepam

(Doral)

Intermediate:

temazepam (Restoril),

estazolam (Prosom),

Short-Acting:

triazolam (Halcion)


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CNS Depressants:

Benzodiazepines

Anxiolytic Type

alprazolam (Xanax)

chloridiazepoxide (Librium)diazepam (Valium)

lorazepam (Ativan)

midazolam (Versed)

zolpidem (Ambien) and zaleplon (Sonata)

(nonbenzodiazepine hypnotic agents, share characteristics)


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Miscellaneous sedative-hypnotic

agents

chloral hydrate

dexmedetomidine

diphenhydraminedoxylamine

eszopiclone

CNS D


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CNS Depressants:

Benzodiazepines

Mechanism of Action

Depress CNS activity

Affect hypothalamic, thalamic, and limbic

systems of the brain

Benzodiazepine receptors

CNS D


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CNS Depressants:

Benzodiazepines

Drug Effects

Calming effect on the CNS

Useful in controlling agitation andanxiety

CNS D t


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CNS Depressants:

Benzodiazepines

Therapeutic UsesSedation

Sleep induction

Skeletal muscle relaxationAnxiety relief

Treatment of alcohol withdrawal

Agitation

Depression

Epilepsy

Balanced anesthesia

CNS D t


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CNS Depressants:

Benzodiazepines

Side Effects

Mild and infrequent

Headache DrowsinessDizziness VertigoLethargy

Paradoxical excitement(nervousness) Hangover

effect


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CNS Depressants:

Nursing Implications

Before beginning therapy, perform athorough history regarding allergies, useof other medications,health history, and

medical history.Obtain baseline vital signs and I & O,including supine and erect BPs.

Assess for potential disorders orconditions that may be contraindications,and for potential drug interactions.


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CNS Depressants:


Give 15 to 30 minutes beforebedtime for maximum effectivenessin inducing sleep.

Most benzodiazepines (exceptflurazepam) cause REM rebound anda tired feeling the next day; use with

caution in the elderly.Patients should be instructed toavoid alcohol and other CNS

depressants.


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CNS Depressants:


Check with physician before takingany other medications, including OTCmedications.

It may take 2 to 3 weeks to noticeimproved sleep when takingbarbiturates.

Abruptly stopping these medications,especially barbiturates, may causerebound insomnia.


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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


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CNS Depressants:


Monitor for therapeutic effects

Increased ability to sleep at night

Fewer awakenings

Shorter sleep induction time

Few side effects, such as hangovereffects

Improved sense of well-being becauseof improved sleep

pharmacology cns depressant

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