chapter 13 cns depressant and muscle relaxants - week 5 Flashcards
Central Nervous System Depressants
Sedatives
Drugs that have an inhibitory effect on the
central nervous system (CNS) to the degree that they reduce:
Nervousness
Excitability
Irritability
Hypnotics
Cause sleep
Have much more potent effect on CNS than sedatives have
A sedative can become a hypnotic if given in large enough doses.
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
Sleep
Normal sleep is cyclic and repetitive.
A sleeping person’s response to stimuli is markedly reduced.
Sleep architecture
Rapid eye movement (REM) sleep
Non-REM sleep
REM interference
REM rebound
CNS Depressants: Benzodiazepines
Formerly the most commonly prescribed sedative–hypnotic drugs
Nonbenzodiazepines currently more frequently prescribed
Favourable adverse effect profiles, efficacy, and safety
Classified as either sedative–hypnotic or anxiolytic (medication that relieves anxiety)
Benzodiazepines: Sedative–Hypnotic Types
Long acting
clonazepam (Rivotril®), diazepam (Valium®), flurazepam hydrochloride (Dalmane®)
Intermediate acting
alprazolam (Xanax®), bromazepam (Lectopam®), lorazepam (Ativan®), temazepam (Restoril®)
Short acting
midazolam hydrochloride, triazolam, zolpidem tartrate (Sublinox®)
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 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
Agitation or anxiety relief
Anxiety-related depression
Benzodiazepines: Uses
Treatment of acute seizure disorders
Treatment of alcohol withdrawal
Short-term therapy for insomnia
Benzodiazepines: Adverse Effects
Mild and infrequent
Headache
Drowsiness
Paradoxical excitement of nervousness
Dizziness
Cognitive impairment
Vertigo
Lethargy
Fall hazard for older adults
“Hangover” effect or daytime sleepiness
Benzodiazepines: Toxicity and Overdose
Somnolence
Confusion
Coma
Diminished reflexes
Rarely results in hypotension and respiratory depression unless taken with other CNS depressants
Treatment symptomatic and supportive
Flumazenil as an antidote
Benzodiazepines: Interactions
Azole antifungals, verapamil, diltiazem, protease inhibitors, macrolide antibiotics, grapefruit juice
CNS depressants (alcohol, opioids, muscle relaxants)
Kava and valerian
Food–drug interactions with grapefruit and grapefruit juice
diazepam (Valium®)
First clinically available benzodiazepine drug. It has varied uses, including treatment of anxiety.
Midazolam
Most commonly used preoperatively and for procedural sedation
Causes amnesia and anxiolysis (reduced anxiety) as well as sedation
Normally administered by IV in adults
Liquid oral dosage form is also available for children.
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.
nonbenzodiazepine: Ramelteon®
Structurally similar to the hormone melatonin; works as an agonist at melatonin receptors in the CNS
Not available in Canada.
Technically, not a CNS depressant; used as hypnotic
Not classified as a controlled substance
Indicated for patients who have difficulty with sleep onset rather than maintenance
Nonbenzodiazepine: zopiclone (Imovane®, Rhovane®)
Short-acting benzodiazepinelike drug
Unique advantage of this drug stems from its very short half-life.
Short-term treatment of insomnia, 7 to 10 days.
Nonbenzodiazepine: zolpidem tartrate (Sublinox®)
Short-acting nonbenzodiazepine hypnotic
Lower incidence of daytime sleepiness compared with benzodiazepine hypnotics
Onset of action approximately 30 minutes
Herbal Products: Kava
Used to relieve anxiety, stress, and restlessness and to promote sleep
May cause temporary yellow skin discoloration (extended, continued intake), scaly skin, 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.
Herbal Products: Valerian
Used to relieve anxiety, restlessness, and sleep disorders
May cause CNS depression, hepatotoxicity, nausea, vomiting, anorexia, headache, restlessness, insomnia
Many interactions, including with CNS depressants, monoamine oxidase inhibitors (MAOIs), phenytoin, warfarin, and alcohol
Contraindicated in cardiac and liver disease
Patient should not operate heavy machinery during use.
Barbiturates
First introduced in 1903; were the standard drugs for insomnia and sedation
Habit forming; low therapeutic index
Only a few commonly used today partly because of the safety and efficacy of benzodiazepines
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.
Barbiturates: Indications
Sedatives
Anticonvulsants
Anaesthesia for surgical procedures
Barbiturates: Adverse Effects
Body system/adverse effects
Cardiovascular: Vasodilation, hypotension
CNS: Drowsiness, lethargy, vertigo
Respiratory: Respiratory depression, cough
Gastrointestinal: Nausea, vomiting, diarrhea, constipation
Hematological: Agranulocytosis, thrombocytopenia
Other: Hypersensitivity reactions, Stevens-Johnson syndrome
Barbiturates: Toxicity and Overdose
Rarely used
Overdose frequently leads to respiratory depression and subsequent respiratory arrest
Overdose produces CNS depression (sleep to coma and death)
Can be therapeutic for:
Anaesthesia induction
Uncontrollable seizures
Pentobarbital or phenobarbital coma
Treatment of overdose
Symptomatic and supportive
Maintain adequate airway
Assisted ventilation or oxygen therapy
Fluids
Alkalization
Activated charcoal
