Chapter 12 Central Nervous System Depressants and Muscle Relaxants Flashcards Preview

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Flashcards in Chapter 12 Central Nervous System Depressants and Muscle Relaxants Deck (32):
1

Sedatives

-Drugs that have an inhibitory effect on the CNS to the degree that they reduce:
Nervousness
Excitability
Irritability

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CNS Depressants: Benzodiazepines

-Formerly the most commonly prescribed sedative-hypnotic drugs
-Favorable drug effect profiles, efficacy, and safety
-Classified as either:
Sedative-hypnotic
Anxiolytic (medication that relieves anxiety)

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Benzodiazepines: Mechanism of Action

-Depress CNS activity
-Affect hypothalamic, thalamic, and limbic systems of the brain
-Benzodiazepine receptors
Gamma-aminobutyric acid (GABA)
-Do not suppress rapid eye movement (REM) sleep as much as barbiturates do
-Do not increase metabolism of other drugs

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Benzodiazepines: Drug Effects

-Calming effect on the CNS
-Useful in controlling agitation and anxiety
-Reduce excessive sensory stimulation, inducing sleep
-Induce skeletal muscle relaxation

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Diazepam (Valium)

First clinically available benzodiazepine drug. It has varied uses, including treatment of anxiety.

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Midazolam (Versed)

-Most commonly used preoperatively and for moderate sedation.
-Causes amnesia and anxiolysis (reduced anxiety) as well as sedation.
-Normally administered by injection in adults
-Liquid oral dosage form is also available for children.

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Temazepam (Restoril)

-Intermediate-acting benzodiazepine
-One of the metabolites of diazepam
-Normally induces sleep within 20 to 40 minutes
-Long onset of action, so it is recommended that patients take it about 1 hour prior to going to bed
-Still an effective hypnotic; however, it has been replaced by newer drugs

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Nonbenzodiazepine: Eszopiclone (Lunesta)

-First hypnotic to be FDA approved for long-term use
-Designed to provide a full 8 hours of sleep
-Considered a short- to intermediate-acting agent
-Patients should allot 8 hours of sleep time and should avoid taking hypnotics when they must awaken in less than 6 to 8 hours.

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Nonbenzodiazepine: Ramelteon (Rozerem)

-Structurally similar to the hormone melatonin: works as an agonist at melatonin receptors in the CNS
-Technically, it is not a CNS depressant; used as hypnotic
-Not classified as a controlled substance
-Indicated for patients who have difficulty with sleep onset rather than sleep maintenance

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Nonbenzodiazepine: Zaleplon (Sonata)

-Short-acting nonbenzodiazepine hypnotic
-Unique advantage of this drug stems from its very short half-life
-Patients whose sleep difficulties include early awakenings can take a dose in the middle of the night as long as it is at least 4 hours before they must arise.

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Nonbenzodiazepine: Zolpidem (Ambien)

-Short-acting nonbenzodiazepine hypnotic
-Lower incidence of daytime sleepiness compared with benzodiazepine hypnotics
-Ambien CR is a longer acting form with two separate drug reservoirs
-Somnambulation

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Herbal Products: Kava

-Used to relieve anxiety, stress, and restlessness and to promote sleep
-May cause temporary yellow skin discoloration (extended, continued intake) and visual disturbances
-Potential interactions with alcohol, barbiturates, and psychoactive drugs
-Contraindicated in liver disease, alcoholism, other conditions
-Patient should not operate heavy machinery during use.

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Herbal Products: Valerian

-Used to relieve anxiety, restlessness, and sleep disorders
-May cause CNS depression, hepatotoxicity, nausea, vomiting, anorexia, restlessness, insomnia
-Many interactions, including with CNS depressants, -MAOIs, phenytoin, warfarin, and alcohol
-Contraindicated in cardiac and liver disease
-Patient should not operate heavy machinery during use.

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Barbiturates

-First introduced in 1903; were the standard drugs for insomnia and sedation
-Habit forming; low therapeutic index
-Only a handful commonly used today partly because of the safety and efficacy of benzodiazepines

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Barbiturates:Mechanism of Action

-Site of action: brainstem (reticular formation)
-By potentiating the action of GABA, nerve impulses traveling in the cerebral cortex are inhibited.

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Barbiturates: Drug Effects

-Low doses: sedative effects
-High doses: hypnotic effects (also lower respiratory rate)
-Notorious enzyme inducers
-Stimulate liver enzymes that cause metabolism or breakdown of many drugs
-Result in shortened duration of action

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Ultrashort acting Barbiturates

Anesthesia for short surgical procedures, other uses

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Short Acting Barbiturates

Sedation and control of convulsive conditions

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Intermediate Acting Barbiturates

Sedation and control of convulsive conditions

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Long Acting Barbiturates

Sleep induction, epileptic seizure prophylaxis

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Barbiturates: Adverse Effects

Cardiovascular Vasodilation, hypotension

CNS Drowsiness, lethargy, vertigo

Respiratory Respiratory depression, cough

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Barbiturates: Adverse Effects (Cont.)

GI Nausea, vomiting, diarrhea, constipation
Hematologic Agranulocytosis, thrombocytopenia

Other Hypersensitivity reactions, Stevens-Johnson syndrome

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Treatment of overdose for Barbiturates

-Symptomatic and supportive
-Maintain adequate airway
-Assisted ventilation or oxygen therapy
-Fluids
-Pressor support
-Activated charcoal

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Inhibited metabolism


MAOIs prolong the effects of barbiturates.

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Common Barbiturates

-Pentobarbital (Nembutol)
- Phenobarbital

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Pentobarbital (Nembutal)

-Prototypical barbiturate
-Long-acting drug
-Uses: prevention of generalized tonic-clonic seizures and fever-induced convulsions, as well as treatment of hyperbilirubinemia in neonates
-Rarely used today as a sedative and is no longer recommended to be used as a hypnotic drug

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Over-the-Counter Hypnotics

-Nonprescription sleeping aids often contain antihistamines, which have CNS depressant effect.
-Doxylamine (Unisom) and diphenhydramine (Sominex), acetaminophen/diphenhydramine (Extra Strength Tylenol PM)
-As with other CNS depressants, concurrent use of alcohol can cause respiratory depression or arrest.

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Low therapeutic index

Drugs with a low therapeutic index have only a narrow dosage range within which the drug is effective; above that range, they are rapidly toxic. `

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Muscle Relaxants

-Act to relieve pain associated with skeletal muscle spasms
-Majority are centrally acting
CNS is the site of action
Similar in structure and action to other CNS depressants
-Direct acting
Act directly on skeletal muscle
Closely resemble GABA

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Muscle Relaxants: Indications

-Relief of painful musculoskeletal conditions
Muscle spasms
Management of spasticity of severe chronic disorders (multiple sclerosis, cerebral palsy)
-Work best when used along with physical therapy

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Muscle Relaxants: Adverse Effects

Extension of effects on CNS and skeletal muscles
-Euphoria
-Lightheadedness
-Dizziness
-Drowsiness
-Fatigue
-Muscle weakness, others

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Nursing Implications

-Give hypnotics 30 to 60 minutes before bedtime for maximum effectiveness in inducing sleep (depends on drug’s onset).
-Most benzodiazepines cause REM rebound and a tired feeling the next day; use with caution in older adults.
-Rebound insomnia may occur for a few nights after a 3- to 4-week regimen has been discontinued