1. Central Nervous System Depressants and Muscle Relaxants
Chapter 12
Central Nervous System Depressants and Muscle Relaxants
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2. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
CNS Depressants
Sedatives
Drugs that have an inhibitory effect on the CNS to the degree that they reduce:
Nervousness
Excitability
Irritability
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3. CNS Depressants (cont’d)
Hypnotics
Cause sleep
Much more potent effect on CNS than sedatives
A sedative can become a hypnotic if it is given in large enough doses
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4. CNS Depressants (cont’d)
Sedative-hypnotics—dose dependent
At low doses, calm the CNS without inducing sleep
At high doses, calm the CNS to the point of causing sleep
Classified into three main groups:
Barbiturates
Benzodiazepines
Miscellaneous drugs
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Sleep
Normal sleep is cyclic and repetitive
A sleeping person is unaware of sensory stimuli within the immediate environment
Sleep architecture
Rapid eye movement (REM) sleep
Non-REM sleep
REM interference
REM rebound
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6. CNS Depressants: Benzodiazepines
Formerly the most commonly prescribed sedative-hypnotic drugs
Nonbenzodiazepines currently more frequently prescribed
Favorable drug effect profiles, efficacy, and safety
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Benzodiazepines
Classified as either:
Sedative-hypnotic
Anxiolytic (medication that relieves anxiety)
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8. Benzodiazepines: Sedative-Hypnotic Types
Long-acting
diazepam (Valium), clonazepam (Klonopin)
Intermediate-acting
alprazolam (Xanax), lorazepam (Ativan), temazepam (Restoril)
Short-acting
midazolam (Versed), triazolam (Halcion)
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9. 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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10. 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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11. Benzodiazepines: Indications
Sedation
Sleep induction
Skeletal muscle relaxation
Anxiety relief
Anxiety-related depression
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12. Benzodiazepines: Indications (cont’d)
Treatment of acute seizure disorders
Treatment of alcohol withdrawal
Agitation relief
Balanced anesthesia
Moderate/conscious sedation
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13. Benzodiazepines: Adverse Effects
Mild and infrequent
Headache
Drowsiness
Dizziness
Cognitive impairment
Vertigo
Lethargy
Fall hazard for elderly persons
“Hangover” effect/daytime sleepiness
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14. Classroom Response Question
When providing education to the patient on the use of a benzodiazepine medication, the nurse will include which information?
These medications have little effect on the normal sleep cycle.
Using this medication may cause drowsiness the next day.
It is safe to drive while taking this medication.
These drugs are safe to use with alcohol.
Correct answer: B
Rationale: Benzodiazepines interfere with REM sleep and may cause a “hangover” effect or next-day drowsiness. They should not be used with alcohol, and persons taking these drugs should not drive.
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15. Benzodiazepines: Toxicity and Overdose
Somnolence
Confusion
Coma
Diminished reflexes
Do not cause hypotension and respiratory depression unless taken with other CNS depressants
Treatment symptomatic and supportive
Flumazenil as an antidote
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16. Benzodiazepines: Interactions
Azole antifungals, verapamil, diltiazem, protease inhibitors, macrolide antibiotics, grapefruit juice
CNS depressants (alcohol, opioids)
olanzapine
rifampin
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17. CNS Depressants: Nonbenzodiazepine Hypnotics
Share many characteristics of benzodiazepines
Used to treat insomnia
Examples: zaleplon (Sonata), zolpidem (Ambien), eszoplicone (Lunesta), and ramelteon (Rozerem)
Eszoplicone and extended-release zolpidem (Ambien CR) approved for long-term therapy
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18. CNS Depressants: Nonbenzodiazepine Hypnotics (cont’d)
Ramelteon (Rozerem)
Does not cause CNS depression
No potential for abuse
No withdrawal signs and symptoms
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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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20. 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, 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 due in part to the safety and efficacy of benzodiazepines
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22. 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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23. 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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24. Barbiturates: Indications
Sedatives
Anticonvulsants
Anesthesia for surgical procedures
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25. Barbiturates: Four Categories
Ultrashort-acting
Anesthesia for short surgical procedures, other uses
Short-acting
Sedation and control of convulsive conditions
Intermediate-acting
Long-acting
Sleep induction, epileptic seizure prophylaxis
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26. Barbiturates: Adverse Effects
Body System Adverse Effects Cardiovascular Vasodilation, hypotension CNS Drowsiness, lethargy, vertigo Respiratory Respiratory depression, cough
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27. Barbiturates: Adverse Effects (cont’d)
Body System Adverse Effects
GI Nausea, vomiting, diarrhea, constipation
Hematologic Agranulocytosis, thrombocytopenia
Other Hypersensitivity reactions, Stevens-Johnson syndrome
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28. Barbiturates: Adverse Effects (cont’d)
Reduced REM sleep, resulting in:
Agitation
Inability to deal with normal stress
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29. Classroom Response Question
An elderly patient taking multiple medications has a barbiturate added to his medication regimen. When administering a barbiturate to an elderly patient, the nurse should expect
a decrease in dosages of the other medications.
the patient will experience increased amounts of REM sleep.
to administer half of the usual dose of the barbiturate.
total relief of anxiety.
Correct answer: C
Rationale: Barbiturates are associated with an increased incidence of falls when used in the elderly; therefore, the usual dose is reduced by half whenever possible. Because barbiturates stimulate the action of enzymes in the liver, drugs are usually broken down more quickly, sometimes requiring the dose to be increased. Patients taking barbiturates have decreased amounts of REM sleep and often experience paradoxical restlessness or excitement.
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30. Barbiturates: Toxicity and Overdose
Overdose frequently leads to respiratory depression and subsequent respiratory arrest
Overdose produces CNS depression (sleep to coma and death)
Can be therapeutic
Anesthesia induction
Uncontrollable seizures: “phenobarbital coma”
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31. Barbiturates: Toxicity and Overdose (cont’d)
Treatment of overdose
Symptomatic and supportive
Maintain adequate airway
Assisted ventilation/oxygen therapy
Fluids
Pressor support
Activated charcoal
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32. Barbiturates: Drug Interactions
Additive effects
Alcohol, antihistamines, benzodiazepines, opioids, tranquilizers
Inhibited metabolism
MAOIs will prolong effects of barbiturates
Increased metabolism
Reduces anticoagulant response, leading to possible clot formation
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Common Barbiturates
pentobarbital (Nembutol)
phenobarbital
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34. Classroom Response Question
Barbiturates have a low therapeutic index. This means
low doses are not therapeutic.
the toxic range is narrow.
they are habit forming.
the effective, safe dosage range is narrow.
Correct answer: D
Rationale: 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. Barbiturates are habit forming, but this is not related to the therapeutic index.
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35. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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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36. 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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37. Muscle Relaxants: Adverse Effects
Extension of effects on CNS and skeletal muscles
Euphoria
Lightheadedness
Dizziness
Drowsiness
Fatigue
Muscle weakness, others
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38. Common Muscle Relaxants
baclofen (Lioresal)
cyclobenzaprine (Flexeril)
dantrolene (Dantrium)
metaxalone (Skelaxin)
tizanidine (Zanaflex)
carisoprodol (Soma)
chlorzoxazone (Paraflex)
methocarbamol (Robaxin)
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39. Classroom Response Question
Which statement regarding muscle relaxants does the nurse identify as being accurate?
Baclofen (Lioresal) is available as an injectable form for use with an implantable pump device.
Cyclobenzaprine (Flexeril) produces little sedation.
Patients taking muscle relaxants are at high risk to develop hypertension.
Patients taking muscle relaxants should be told to stop taking the medication if they feel sleepy.
Correct answer: A
Rationale: Baclofen (Lioresal) is sometimes used in an injectable form. Cyclobenzaprine (Flexeril) often results in deep sedation and sleepiness. Patients taking muscle relaxants are at risk to develop hypotension; therefore, they should be taught safety measures to prevent falls. Sedation and sleepiness are common side effects of muscle relaxants; however, a patient should not abruptly discontinue use of the medication. Safety procedures should be followed to prevent accidents and falls.
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Nursing Implications
Before beginning therapy, obtain 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
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41. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
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 the elderly
Instruct patients to avoid alcohol and other CNS depressants
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42. Nursing Implications (cont’d)
Check with prescriber before taking any other medications, including over-the-counter medications
Rebound insomnia may occur for a few nights after a 3- to 4-week regimen has been discontinued
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43. Nursing Implications (cont’d)
Safety is important
Keep side rails up or use bed alarms
Do not permit smoking
Assist patient with ambulation (especially the elderly)
Keep call light within reach
Monitor for adverse effects
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44. Nursing Implications (cont’d)
Monitor for therapeutic effects
Increased ability to sleep at night
Fewer awakenings
Shorter sleep-induction time
Few adverse effects, such as “hangover” effects
Improved sense of well-being because of improved sleep
For muscle relaxants:
Decreased spasticity, decreased rigidity
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