ch 12 cns depressants and muscle relaxants

cns depressants/sedatives

• inhibitory effect on CNS

  • reduces nervousness, excitability, irritability

hypnotics

• causes sleep

• more potent than sedatives

• sedative can become hypnotic if large doses are given

sedative-hypnotics

• dose dependent

• low doses → calms CNS without inducing sleep

• high doses → calms CNS and induces sleeps

• three types

  • barbiturates

  • benzodiazepines (many end in “pam”)

  • miscellaneous drugs

sleep

• transient, reversible periodic state of rest

• ↓ in physical activity and LOC

• cyclic and repetitive

• sleeping person unaware of sensory stimuli in environment

rapid eye movement (rem)

• stage of sleep where we have movement of eyes under eyelids

• when we dream, muscles are paralyzed

• helps consolidate memories

• emotional regulation

non rem sleep

• n1

  • wakefulness to sleep

• n2

  • period of light sleep

• n3

  • deep sleep

• stress, alcohol, medications can interfere

• rem sleep deprivation → rem rebound (intensity + proportion of rem sleep increases)

benzodiazepines

• formerly most commonly prescribed sedative-hypnotic drug

  • nonbenzos now more frequently prescribed for people who can’t sleep

• favorable effects, efficacy and safety when used properly

• for sleep or for anxiety

benzodiazepine MOA

• depress CNS activity

• affect hypothalmic, thalamic, and limbic parts of brain

  • emotions, alertness, sleep

• benzodiazepine receptors

  • GABA

  • neurons less likely to fire

• do not suppress REM as much as barbituates

• do not increase metabolism of other drugs

• calming effect

• for agitation and anxiety

• reduces excessive sensory stimulation (helps with sleep)

• skeletal muscle relaxation (muscle spasms)

• very versatile!

benzodiazepine indications

• sedation

• sleep induction

• skeletal muscle relaxation

• anxiety relief

• anxiety-related depression

• seizures

• alc withdrawal

• agitation

• balanced anesthesia

• moderate or conscious sedation

benzodiazepine contraindications

• drug allergy

• narrow angle glaucoma (can increase intraocular pressure)

• pregnancy

benzodiazepine adverse effects

• mild and infrequent

  • headache

  • drowsiness

  • cognitive impairment

  • vertigo

  • lethargy

  • fall hazard for oldr adults

  • “hangover” effect, daytime sleepiness

benzodiazepine toxicity/overdose + interactions

• somnolence, confusion, coma, diminished reflexes

• don’t cause hypotension and resp depression unless taken w/ other cns depressants

• treatment for symptoms and support

  • flumazenil antidote for overdose

• interactions: things metabolized by liver, opioids, etoh, azoles, herbals, high protein meals

diazepam (valium)

• first clinically available benzo for anxiety, anesthesia adjunct, anticonvulsant and muscle relaxer (PO, IM, PR)

midazolam (versed)

• used for sedation, causes ammnesia (IV, liquid for peds)

• conscious sedation

temazepam (restoril)

• intermediate acting, sleep inducted in 20-40 min

nonbenzodiazepines (hypnotics)

• sleep purposes only

• eszopiclone (lunesta)

• ramelteon (rozeraem)

• zolpidem (ambien)

eszopiclone (lunesta)

• first hypnotic to be fda approved

ramelteon (rozerem)

• similar to hormone melatonin.

• works as agonist at melatonin receptors in CNS

zolpidem (ambien)

• lower incidence of daytime sleepiness compaired to benzos

barbiturates

• standard drugs for insomnia and sedation

• low therapeutic index; habit forming (if you slightly go over index → side effects)

• only few are used due to the safety/efficacy of benzos

barbiturate indications

• ultrashort

  • anesthesia for short surgical procedures

  • anesthesia induction

  • convulsion control

  • reduction of intracranial pressure in neuro pts

• short

  • sedation + control of convulsive conditions

• intermediate

  • sedation + control of convulsive conditions

• long

  • epileptic seizure prophylaxis

barbiurate contraindications

• drug allergy

• pregnancy

• significant resp difficulties

• severe kidney/liver disease

• caution in older adults

barbiturates adverse effects

• cardio: vasodilation, hypotension

• cns: drowsines, lethargy, vertigo, reduced REM → agitation

• resp: resp depression, cough

• gi: nauseam vomiting, diarrhea, constipation

• hematology: agranulocytosis, thrombocytopenia

• other: hypersensitivity, stevens-johnson syndrome

• (why they are less commonly used now)

barbiturates toxicity/overdose

• overdose → resp depression → resp arrest

• overdose → cns depression → sleep to coma and death

• can be therapeutic

  • anesthesia induction

  • uncontrollable seizures or severe head injury → phenobarbital coma

• treatment: symptoms and support. maintain airway, ventilation, o2 therapy, fluids, pressors, urine alkalization to hasten elimination

barbiturates drug interactions

• additive effects

  • alcohol, anti-histamines, benzos, opioids, tranquilizers

• inhibited metabolism

  • MAOIs prolong effects, stays in the body longer

• increased metabolism (enzyme inducers)

  • reduces anti-coagulant response → leading to possible clot formation

pentobarbital (nembutal)

• long acting drug

• for pre-op anxiety and sedation

• status epilepticus

• no longer used as sedative hypnotic for insomnia

• not typically prescribed to take at home

otc hypnotics

• often contain anti-histamines (have cns depressant effect)

• doxylamine (unisom) and deiphenhydramine (sominex/benadryl)

• acetaminophen/diphenhydramine

• melatonin (extra strength tylenol pm)

• concurrent use w/ alcohol can cause resp depression or arrest

muscle relaxants

• relieves pain assoc w/ skeletal muscle spasms

• structurally/functionally similar to other cns depressants

• act directly on muscle and fibers and contractile process

• resemble GABA and attaches to receptors to cause sedation

muscle relaxant indications

• relief of painful musculoskeletal conditions

• works best alongside physical therapy to retrain those muscles!!

muscle relaxants adverse effects

• extension of effects of CNS and skeletal muscles

• euphoria

• lightheadedness

• dizziness

• drowsiness

• fatigue

• muscle weakness

muscle relaxant toxicity/overdose

• involve the CNS

• no antidote/reversal

• if taken w/ other depressants

  • airway must be maintained

  • ekg

  • fluids to avoid crystalluria

• caution w/ other cns depressants

  • benzos

  • alcohol

common muscle relaxants

• baclofen (lioresal) **

• cyclobenzaprine (flexeril) **

• dantrolene (dantrium) **

  • for malignant hyperthermia cases

• metaxalone (skelaxin)

• tizanidine (zanaflex)

• carisoprodol (soma)

• chlorzoxazone (paraflex)

• methocarbamol (robaxin)

nursing implications

• obtain thorough hx of allergies, meds, health history and medical history

• baseline vitals, i&o, supine/erect blood pressure

• assess for conditions that contraindicate and drug interactions

• give hypnotic 30-60 min before bed time

• most benzos cause rem rebound

• avoid alc and other cns depressants!!

• check w/ hcp before taking any other meds (otc too!)

• rebound insomnia may occur after 3-4 regimen discontinued

• keep side rails up & use bed alarms

• no smoking!

• assist w/ ambulation

• monitor for adverse effects

monitor for therapeutic effects

• increased ability to sleep at night

• fewer awakenings

• shorter sleep induction time

• fewer adverse effects (hangover)

• improved sense of well-being due to sleep

• for muscle relaxants: decreased spasticity, decreased rigidity