1. Central Nervous System (CNS) Depressants and Muscle Relaxants
Chapter 12
Central Nervous System (CNS) Depressants and Muscle Relaxants
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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.)
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.)
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 are currently more frequently prescribed
Favorable drug effect profiles, efficacy, and safety
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7. CNS Depressants: Benzodiazepines (Cont.)
Classified as either:
Sedative-hypnotic
Anxiolytic (medication that relieves anxiety)
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8. Benzodiazepines: Sedative-Hypnotic Types
Long acting
Clonazepam (Klonopin), diazepam (Valium), flurazepam (Dalmane)
Intermediate acting
Alprazolam (Xanax), lorazepam (Ativan), temazepam (Restoril)
Short acting
Midazolam (Versed), triazolam (Halcion),eszopiclone (Lunesta), ramelteon (Rozerem), zaleplon (Sonata), zolpidem (Ambien)
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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.)
Treatment of acute seizure disorders
Treatment of alcohol withdrawal
Agitation relief
Balanced anesthesia
Moderate or conscious sedation
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13. Benzodiazepines: Adverse Effects
Mild and infrequent:
Headache
Drowsiness
Dizziness
Cognitive impairment
Vertigo
Lethargy
Fall hazard for older adults
“Hangover” effect or daytime sleepiness
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14. Audience Response System 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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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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20. 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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21. 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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22. 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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23. 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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25. 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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27. 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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28. 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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29. Barbiturates: Indications
Sedatives
Anticonvulsants
Anesthesia for surgical procedures
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30. 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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31. Barbiturates: Adverse Effects
Body System Adverse Effects Cardiovascular Vasodilation, hypotension CNS Drowsiness, lethargy, vertigo Respiratory Respiratory depression, cough
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32. Barbiturates: Adverse Effects (Cont.)
Body System Adverse Effects
GI Nausea, vomiting, diarrhea, constipation
Hematologic Agranulocytosis, thrombocytopenia
Other Hypersensitivity reactions, Stevens-Johnson syndrome
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33. Barbiturates: Adverse Effects (Cont.)
Reduced REM sleep, resulting in:
Agitation
Inability to deal with normal stress
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34. Audience Response System Question
An older adult patient taking multiple medications has a barbiturate added to his medication regimen. When administering a barbiturate to an older adult, 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 older adults; 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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35. 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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36. Barbiturates: Toxicity and Overdose (Cont.)
Treatment of overdose
Symptomatic and supportive
Maintain adequate airway
Assisted ventilation or oxygen therapy
Fluids
Pressor support
Activated charcoal
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37. Barbiturates: Drug Interactions
Additive effects
Alcohol, antihistamines, benzodiazepines, opioids, tranquilizers
Inhibited metabolism
MAOIs prolong the 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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39. 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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40. 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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41. Audience Response System 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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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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43. 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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44. Muscle Relaxants: Adverse Effects
Extension of effects on CNS and skeletal muscles
Euphoria
Lightheadedness
Dizziness
Drowsiness
Fatigue
Muscle weakness, others
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45. Common Muscle Relaxants
Baclofen (Lioresal)
Cyclobenzaprine (Flexeril)
Dantrolene (Dantrium)
Metaxalone (Skelaxin)
Tizanidine (Zanaflex)
Carisoprodol (Soma)
Chlorzoxazone (Paraflex)
Methocarbamol (Robaxin)
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46. Audience Response System 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 of developing 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 blood pressure.
Assess for potential disorders and conditions that may be contraindications and for potential drug interactions.
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48. Nursing Implications (Cont.)
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.
Instruct patients to avoid alcohol and other CNS depressants.
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49. Nursing Implications (Cont.)
Check with the 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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50. Nursing Implications (Cont.)
Safety is important:
Keep side rails up or use bed alarms.
Do not permit smoking.
Assist patient with ambulation (especially older adults).
Keep call light within reach.
Monitor for adverse effects.
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51. Nursing Implications (Cont.)
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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Case Study
A patient comes to the health care provider’s office with complaints of feeling anxious and having difficulty sleeping. The patient tells the nurse that he wants to start taking valerian and Kava because he heard that these work well to help the problems he is experiencing. The patient has the following questions about valerian and Kava. What is the best response by the nurse?
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Case Study (Cont.)
The patient asks, “Is there anything I have to worry about when taking Kava?” The best response by the nurse is:
“Kava is a natural product which has no side effects.”
“You need a prescription to take Kava.”
“No worries, Kava is recommended for patients with depression.”
“It is best to inform you health care provider of any additional medication or supplements you plan to take to check for interactions that may be harmful.”
Correct answer: 4
Rationale: Even natural products have side effects. Side effects of Kava include skin discoloration, possible accommodative disturbances and pupillary enlargement, and scaly skin (with long-term use). Kava and other supplements are available without a prescription. Kava is contraindicated in patients with Parkinson’s disease, liver disease, depression, or alcoholism; in those operating heavy machinery; and in pregnant and breastfeeding women. As with all medications and supplements, it is best to inform the health care provider to evaluate possible interactions among drugs and supplements taken.
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Case Study (Cont.)
The patient tells the nurse that his friend has been taking valerian for a long period of time and that he isn’t feeling so well. The patient asks the nurse what the adverse effects of valerian are. The best response by the nurse is that adverse effects of valerian include
insomnia.
yellow skin.
bruising.
increased appetite.
Correct answer: 1
Rationale: Adverse effects of valerian include CNS depression, hepatotoxicity, nausea, vomiting, anorexia, headache, restlessness, and insomnia.
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