Module 3 Central Nervous System Depressants Flashcards
CNS Depressants
Sedatives
Drugs that have an inhibitory effect on the
CNS to the degree that they reduce:
Nervousness
Excitability
Irritability without causing sleep
Hypnotics
Cause sleep
sedative can become a hypnotic it is given in large enough dose
Sedative-hypnotics—dose dependent
At low doses, calm the CNS without inducing sleep
At high doses, calm the to the point of causing sleep
Barbiturates
Benzodiazepines
Sleep
Normal sleep is cyclic and repetitive A sleeping person is unaware of sensory stimuli within the immediate environment Rapid eye movement (REM) sleep Non–rapid eye movement (non-REM) sleep Sleep stages REM rebound
CNS Depressants:
Benzodiazepines
A commonly prescribed drug class Favorable drug effect profiles, efficacy, and
safety
Benzodiazepines:
Classification
Classified as either:
sedative-hypnotic
Anxiolytic (medication that relieves anxiety)
Benzodiazepines:
Sedative-Hypnotic Types
Long-acting
estazolam (Prosom), flurazepam (Dalmane),
lorazepam (Ativan)
Short-acting
temazepam (Restoril), alprazolam (Xanax),
triazolam (Halcion
CNS Depressants:
Nonbenzodiazepine Hypnotics
Share many characteristics of benzodiazepines
Used to treat insomnia
Examples: zaleplon (Sonata), zolpidem (Ambien),
eszopiclone (Lunesta), and ramelteon (Rozerem)
Eszopiclone and extended-release zolpidem (Ambien CR) approved for long-term therapy
CNS Depressants:
Nonbenzodiazepine Hypnotics
Ramelteon (Rozerem)
Does not cause CNS depression
No potential for abuse
No withdrawal signs and symptoms
Benzodiazepines:
Mechanism of Action
Depress CNS activity
Affect hypothalamic, thalamic, and limbic
systems of the brain
Benzodiazepine receptors
Do not suppress REM sleep as much as barbiturates do
Do not increase metabolism of other drugs
Benzodiazepines:
Drug Effects
Calming effect on the CNS Useful in controlling agitation and anxiety Reduce excessive sensory stimulation, inducing sleep Induce skeletal muscle relaxation
Benzodiazepines:
Indications
Sedation Sleep induction Skeletal muscle relaxation Anxiety relief Treatment of alcohol withdrawal Agitation Depression Epilepsy Balanced anesthesia Moderate/conscious sedation
Benzodiazepines: Adverse
Effects
Mild and infrequent Headache Drowsiness Dizziness Vertigo Lethargy Fall hazard for frail elderly persons “Hangover” effect/daytime sleepiness
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
Herbal Products: Kava
Used to relieve anxiety, stress, and restlessness, and to promote sleep
May cause temporary yellow skin discoloration(extended, continued intake)
May cause visual disturbances
Potential interactions with alcohol, barbiturates, and psychoactive drugs
Contraindicated in liver disease, alcoholism, other conditions
Patient should not operate heavy machinery during
Herbal Products: Valerian
Used to relieve anxiety, restlessness, and sleep
disorders
May cause CNS depression, hepatotoxicity, nausea,
vomiting anorexia restlessness insomnia
vomiting, anorexia, restlessness, Many interactions, including with CNS depressants, MAOIs, phenytoin, warfarin, alcohol
Contraindicated in cardiac and liver disease Patient should not operate heavy machinery duringuse
Sedative-Hypnotics: Barbiturates
First introduced in 1903; were the standard
drugs for insomnia and sedatio
Habit forming; low therapeutic index
Only a handful commonly used today due in
part to the safety and efficacy of
benzodiazepines
Therapeutic Index
Ratio between the toxic and therapeutic
concentrations of a drug
Barbiturates have a very low therapeutic
index
Barbiturates:
Mechanism of Action
Site of action
Brainstem (reticular formation)
By facilitating GABA, nerve impulses traveling in the cerebral cortex are inhibited
Barbiturates: Drug Effects
Low doses: sedative effects
High doses: hypnotic effects (also lower
respiratory rate)
Notorious enzyme inducers
Stimulate liver enzymes that cause the metabolism
or breakdown of many drugs
Result: shortened duration of action
Barbiturates: Indications
Hypnotics
Sedatives
Anticonvulsants
Anesthesia for surgical procedures
Barbiturates: Four Categories
Ultra short-acting
Anesthesia for short surgical procedures
Short-acting
Sedation/sleep induction and control of convulsive
conditions
Intermediate-acting
Sedation/sleep induction and control of convulsive
conditions
Long-acting
Sleep induction, epileptic seizure prophylaxis
Barbiturates: Four Categories
cont’d
Ultrashort methohexital, thiopental Short pentobarbital, secobarbital Intermediate butabarbital Long phenobarbital, mephobarbital
Barbiturates: Onset and Duration
Ultrashort - Onset IV less than 15 mins Duration IV less than 2 hrs Short- Onset PO: 15 to 20 mins Duration PO: 2 to 4 hrs Intermediate-Onset PO: 20 to 30 mins Duration PO: 2 to 4 hrs Long- Onset PO: 30 to 60 mins Duration PO: 6 to 8 hrs
Barbiturates: Adverse Effects
Body System Adverse Effects
CNS Drowsiness, lethargy,vertigo mental depression vertigo, Respiratory Respiratory depression,apnea, bronchospasms,cough
Body System Adverse Effects
GI Nausea, vomiting, diarrhea,constipation
Other Agranulocytosis,
hypotension, Stevens-
Johnson syndrome
Reduced REM sleep, resulting in:
Agitation Inability to deal with normal stress
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” Treatment of overdose Symptomatic and supportive Maintain adequate airway Assisted ventilation/oxygen therapy Fluids Pressor support Activated charcoal
Barbiturates:
Drug Interactions
Additive effects
ETOH, antihistamines, benzodiazepines, opioids
Metabolism inhibited by other drugs
MAOIs will prolong effects of barbiturates
Increased metabolism of other drugs
Reduces anticoagulant response, leading to possible clot formation
Muscle Relaxants
Act to relieve pain associated with skeletal muscle spasms Majority are central-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
Muscle Relaxants: Indications
Relief of painful musculoskeletal conditions
Muscle spasms
Management of spasticity of severe chronic disorders, eg. multiple sclerosis, cerebral palsy
Work best when used along with physical therapy
dantrolene (Dantrium)
Malignant hyperthermia
Muscle Relaxants: Adverse
Effects
Extension of effects on CNS and skeletal muscles Euphoria Lightheadedness Dizziness Drowsiness Fatigue Muscle weakness
Common Muscle Relaxants
baclofen (Lioresal) cyclobenzaprine ( Flexeril) dantrolene (Dantrium) metaxalone (Skelaxin) tizanidine (Zanaflex)
