CNS Depressants

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CNS Depressants and Muscle Relaxants

Non-Rem sleep

Sleep stages 1 through 4, which are marked by an absence of rapid eye movements, relatively little dreaming, and varied EEG activity. Largest portion of the sleep cycle.

Stage 1 non-rem sleep

Light sleep. A transitional stage between waking and sleeping, usually lasts 5-10 minutes. Breathing slows. Heart rate decreases. Eyes exhibit slow rolling movement. 2 -5% of total sleep

Stage 2 non-rem sleep

True sleep. Deeper level when thoughts and images pass through the mind, eye movement stops, and there is very little body movement. 50% of total sleep

Stage 3 non-rem sleep

deep sleep, sleeper is unresponsive, has slow pulse, low blood pressure and lowered body temperature. 5% of total sleep

Stage 4 non-rem sleep

very deep sleep with rhythmic breathing, limited muscle activity. Dreaming occurs during this stage, if person is awakened they may feel groggy. Sleepwalking or bedwetting may occur. 10-15% of total sleep

REM Sleep

Rapid eye movement sleep, a recurring sleep stage during which vivid dreams commonly occur. Breathing may be irregular, vivid dreams occur. 25-33% of total sleep

Barbituates

drugs that depress the activity of the central nervous system, reducing anxiety but imparing memory and judgement

Benzodiazepines

anti-anxiety drugs that depress the central nervous system, reduce activity, and induce relaxation and sleep; often prescribed to relieve tension, muscular strain, sleep problems, anxiety, and panic attacks (eg. valium)

GABA

major inhibitory neurotransmitter found in the brain

Hypnotics

agents that depress central nervous system (CNS) functions, promote sedation and sleep, and relieve agitation, anxiousness, and restlessness

REM Interference

A drug-induced reduction of REM sleep time.

REM Rebound

Excessive REM sleep following discontinuation of a sleep-altering drug.

Benzodiazapine Overdose

Treatment is generally supportive. If ingestion is recent Gastric Lavage is indicated. Activated charcoal and a saline catharic may be administered after GL to remove any remaining drug. Flumazenil, a benzodiazepine antidote may be used to acutely reverse the sedative effects of overdose.

Benzodiazepine Sedative-Hypnotic Types

Short-acting: midazolam (versed), triazolam (Halcion) Versed most commonly used for procedural sedation due to its ability to cause amnesia and reduce anxiety. Halcion used to calm over-active pt.
Intermediate-acting: alprazoloam (Xanax), lorazepam (Ativan), temazepam (Restoril) Xanax most often used for anxiet-related depression. Restoril is most often used for sleep.
Long-acting: diazepam (Valium), conazepam (Klonopin) Valium is commonly requested following a traumatic death of a loved one.

Mechanism of Action: Benzodiazepines

Depress CNS activity. Affect hypothalamic, thalamic, and limbic systems of the brain. Benzo receptors = GABA. Do not suppress REM sleep as much as Barbituates. Don't increase metabolism of other drugs.

Drug Effects of Benzodiazepines

Calming effect on the CNS; useful in controlling agitation and anxiety; reduce excessive sensory stimulation, inducing sleep; induce skeletal muscle relaxation. Overall relaxation

Adverse Effects: Benzodiazepines

Usually mild and infrequent; headache, drowsiness, dizziness, vertigo (dizziness), lethargy, fall hazard for elderly persons, "hangover" effect/daytime sleepiness. Less common adverse effects = palpitations, dry mouth, nausea, vomiting, hypokinesia, occasional nightmares.
Withdrawal symptoms w/ abrupt discontinuation= rebound insomnia

Interactions: Benzodiazepines

Verapamil, diltiazem, protease inhibitors, macrolide antibiotics, azole antifungals, grapefruit juice. Other CNS depressants (alcohol, opioids) olanzapine and rifampin

Non-Benzodiazepine Hypnotics

-Used to treat insomnia
-zalepion (sonata), zolpidem (ambien), eszoplicone (lunesta)
-lunesta approved for long-term treatment of chronic insomnia

Ramelteon (Rozerem)

melatonin agonist - activation of melatonin receptors; doesn't act by CNS depression; used for insomnia with delayed sleep onset; approved for long-term use; less likely to cause daytime sleepiness, no potential for abuse, no withdrawal signs/symptoms.

Kava

relieves anxiety, promotes sleep and relaxes muscles; data support muscle relaxant and antianxiety effects; can cause CNS depression, impair vision, muscle incoordination, scaly skin disorder with prolonged use, can cause hepatitis, cirrhosis, and liver failure; potentiates effects of CNS depressants - avoid with alcohol, opioids, barbituates. May cause temporary yellow skin discoloration.

Valerian

Used to treat nervousness and insomnia. Produces restful sleep without morning "hangover" The root may be used to make a tea, or capsules are available in a variety of dosages. Mechanism of action is similar to benzodiazepines, but without addicting properties. Side effects may include mild HA or upset stomach. Taking doses higher than recommended may result in severe HA, nausea, morning grogginess, blurry vision. Should not be taken concurrently with CNS depressants, MAOI's, phenytoin, warfarin, and alcohol. (Smelly Socks)

Barbituates

introduced in 1900s as sedative, class 2, habit forming, low therapeutic index, only a handful commonly used today, mainly replaced by benzodiazepines. Low doses cause sedative effects, high doses cause hypnotic effects and lower respiratory rate. Uses: Sedatives, anticonvulsants, and anesthesia for surgical procedures.
do not take with Kava, valerian may increase effects.

Common Barbituates

1. Phenobarbital (Lamina)
2. Pentobarbital (Nembutal)

Four catagories of Barbituates

Ultra short-acting- anesthesia for surgical procedures
Short-acting & Intermediate - Sedation and control of convulsive conditions
Long-acting - Sleep induction, epileptic seizure prophylaxis

Adverse Effects: Barbituates

CNS effects - drowsiness, dizziness, lethargy, paradoxical restlessness or excitement.
Cardio - vasodilation, hypotension
Respiratory - respiratory depression, cough
GI - nausea/vomiting, diarrhea, constipation
Hematologic - agranulocytosis, thrombocytopenia
Other - Stevens-Johnsons Syndrome
Additive effect if used with any other CNS depressant drugs.
Hepatic enzyme inducer - causes many drugs to be metabolized more quickly → shortens duration of action
Reduced REM sleep, resulting in: Agitation, Inability to deal with normal stress

Toxcity & Overdose: Barbituates

Overdose leads to respiratory depression and subsequent respiratory arrest, can also cause CNS depression (sleep to coma to death) Can be used therapeutically to induce "phenobarbital coma" in pt's with uncontrollable seizures.

Treatment of overdose of barbituates

Symptomatic and supportive. No specific antidote. Activated Charcoal may be used if caught in time. maintain airway, assist with ventilation/oxygen therapy, fluids, pressor support.

Muscle Relaxants

Act to relieve discomfort from skeletal muscle spasms; Majority act in CNS to depress muscle activation; Acts directly on skeletal muscle; Relief of painful musculoskeletal conditions (spasms, multiple sclerosis, cerebral palsy); Work best when used along with physical therapy

Common muscle relaxants

Cyclobenzaprine (Flexaril), metaxalone (Skelaxin), and tizanidine (Zanaflex) baclofen (Lioresal, dantrolene (Dantrium), carisoprodol (Soma), chlorzoxazone (Paraflex), methocarbamol (Robaxin)

Adverse Effects: Muscle relaxant

Euphoria, lightheadedness, dizziness, drowsiness, fatigue, muscle weakness.

Nursing Implications: CNS Depressants

Obtain baseline VS & I&O, including supine and erect BP's. Assess for disorders/conditions that may be contrindicated and for potential drug interactions. Administer Hypnotics 30 - 60 minutes before bedtime. Use benzodiazepines cautiously with elderly; may cause rebound REM and hang-over feeling. Instruct pts to avoid alcohol and other CNS depressants. Safety is important, raise side rails. No smoking. Assist with ambulation, keep call light close. Monitor for adverse effects as well as therapeutic.

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