Chapter 12 Central Nervous System Depressants and Muscle Relaxants

Question 1

Sedatives

Answer 1

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

Question 2

CNS Depressants: Benzodiazepines

Answer 2

-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)

Question 3

Benzodiazepines: Mechanism of Action

Answer 3

-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

Question 4

Benzodiazepines: Drug Effects

Answer 4

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

Question 5

Diazepam (Valium)

Answer 5

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

Question 6

Midazolam (Versed)

Answer 6

• 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.

Question 7

Temazepam (Restoril)

Answer 7

• 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• Still an effective hypnotic; however, it has been replaced by newer drugs

Question 8

Nonbenzodiazepine: Eszopiclone (Lunesta)

Answer 8

• 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.

Question 9

Nonbenzodiazepine: Ramelteon (Rozerem)

Answer 9

• 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

Question 10

Nonbenzodiazepine: Zaleplon (Sonata)

Answer 10

• 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.

Question 11

Nonbenzodiazepine: Zolpidem (Ambien)

Answer 11

• 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

Question 12

Herbal Products: Kava

Answer 12

• 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.

Question 13

Herbal Products: Valerian

Answer 13

• 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.

Question 14

Barbiturates

Answer 14

• 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

Question 15

Barbiturates:Mechanism of Action

Answer 15

• Site of action: brainstem (reticular formation)

- By potentiating the action of GABA, nerve impulses traveling in the cerebral cortex are inhibited.

Question 16

Barbiturates: Drug Effects

Answer 16

• 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

Question 17

Ultrashort acting Barbiturates

Answer 17

Anesthesia for short surgical procedures, other uses

Question 18

Short Acting Barbiturates

Answer 18

Sedation and control of convulsive conditions

Question 19

Intermediate Acting Barbiturates

Answer 19

Sedation and control of convulsive conditions

Question 20

Long Acting Barbiturates

Answer 20

Sleep induction, epileptic seizure prophylaxis

Question 21

Barbiturates: Adverse Effects

Answer 21

Cardiovascular Vasodilation, hypotension

CNS Drowsiness, lethargy, vertigo

Respiratory Respiratory depression, cough

Question 22

Barbiturates: Adverse Effects (Cont.)

Answer 22

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

Other Hypersensitivity reactions, Stevens-Johnson syndrome

Question 23

Treatment of overdose for Barbiturates

Answer 23

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

Question 24

Inhibited metabolism

Answer 24

MAOIs prolong the effects of barbiturates.

Question 25

Common Barbiturates

Answer 25

- Pentobarbital (Nembutol) | - Phenobarbital

Question 26

Pentobarbital (Nembutal)

Answer 26

- 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

Question 27

Over-the-Counter Hypnotics

Answer 27

- 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.

Question 28

Low therapeutic index

Answer 28

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. `

Question 29

Muscle Relaxants

Answer 29

-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

Question 30

Muscle Relaxants: Indications

Answer 30

-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

Question 31

Muscle Relaxants: Adverse Effects

Answer 31

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

Question 32

Nursing Implications

Answer 32

- 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