central nervous system agents
DESCRIPTION
TRANSCRIPT
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Central Nervous System AgentsMa. Tosca Cybil A. Torres,
RN, MAN
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CNS Stimulant
s
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CNS stimulants are drugs which increase the muscular (motor) and the mental (sensory) activities
Their effects vary from the increase in the alertness and wakefulness (as with caffeine) TO the production of convulsion ( as with strychnine) or death due to over stimulation
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Behavioral Manifestations of CNS Stimulation
• mild elevation in alertness, decrease in drowsiness and lessening of fatigue (Analeptic Effect)
• increased nervousness and anxiety -convulsions.
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Molecular Basis of CNS Stimulation
Imbalance between inhibitory and excitatoryprocesses as in the brain. This hyperexcitability
of neurons results from: • potentiation or enhancement of excitatory
neurotransmission(e.g. amphetamine) • depression or antagonism of inhibitory
transmission (e.g. Strychnine) • presynaptic control of neurotransmitter
release (e.g. picrotoxin)
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Classification of CNS Stimulants
• Analeptic Stimulants– Respiratory Stimulants – Convulsants
• Psychomotor Stimulant– Sympathomimetics or
Adrenergic CNS Stimulants• Methylxanthines
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Analeptic Stimulants• diverse chemical class of agents • majority can be absorbed orally • have a short duration of action -
primary expression of pharmacological effect is convulsions (tonic-clonic) uncoordinated
• pharmacological effect is terminated through hepatic metabolism
• Possible Common Mechanism of Action -ability to alter movement of chloride ions across neuronal membranes
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• Doxapram - used to counteract postanesthetic respiratory depression and for acute hypercapnia in chronic pulmonary disease.– Used with caution with neonatal apnea– Administered IV– Onset of action: within 20-40 secs– SE: (overdose)
• Hypertension• Tachycardia• Trembling• convulsions
Respiratory CNS Stimulants
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Headaches: Migraine and Cluster Migraine headaches-
characterized by a unilateral throbbing head pain, accompanied by N/V and photophobia
Cluster headaches- characterized by severe unilateral nonthrobbing pain usually located around the eye. Usually not associated with N/V
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Preventive Treatment for migraine
1. Beta adrenergic blockers 2. Anticonvulsants- Valproic
acid (Depakote) 3. Tricyclic antidepressants-
amitriptyline (Elavil)
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Treatment or Cessation of Attacks
• Ergotamine tartrate– Nonspecific serotonin agonist and
vasoconstrictor– Should be taken early during a
migraine attack – May cause N and V
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• Triptans– The most common recently developed group of
drugs for tx of migraines and cluster headches– Prototype: sumatriptan(Imitrex)
• Selective serotonin receptor agonist with a short duration of action
• Considered more effective than ergotamine • MOA: causes vasoconstriction of cranial carotid
arteries to relieve migraine attacks• SE: dizziness, fainting, tingling, numbness, warm
sensation, drowsiness• AR: hypotension, heart block, angina, MI, cardiac
arrest
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• Amphetamines–Stimulates the release of
norepinephrine and dopamine from the brain and SNS.
–Can cause euphoria and alertness
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CHARACTERISTICS
• all compounds are absorbed well orally• large portion of untransformed amphetamine is
excreted unchanged in the urine. Consequently, acidifying the urine with ammonium chloride hastens its clearance, and thus reduces its reabsorption in the renal tubules.
• Overdose: hyperreflexia, tremors, convulsions and irritability
• CV problems: increased heart rate, increased BP, palpitations and cardiac dysrythmias
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• Therapeutic Uses:– Narcolepsy
• Characterized by falling asleep during waking hours, such as driving a car or talking with someone. Sleep paralysis, a condition that is normal during sleep usually accompanies narcolepsy which affects the voluntary muscles making the person unable to move and collapse
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• Therapeutic uses: –Attention Deficit/Hyperactivity Disorder
• May be caused by disregulation of serotonin, norepinephrine, and dopamine.
• Occurs primarily in children, usually before the age 7, but may continue through teenage years.
• Characteristics involved include inattentiveness, poor coordination, inability to concentrate, restlessness, hyperactivity (excessive and purposeless activity), inability to complete tasks, and impulsivity.
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Pharmacological Actions
• The primary effects of an oral dose are wakefulness, alertness, decrease fatigue; mood elevation, increased ability to concentrate; an increase in motor and speech activity. Amphetamines also diminish the awareness of fatigue; person may push exertion to the point of severe damage or even death.
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• Stimulate the respiratory center, especially when respiration is depressed by centrally acting drugs, (barbiturates and alcohol).
• Amphetamine can reverse the marked sedation and behavioral retardation resulting from reserpine-like drug.
• Depresses appetite by their action on the lateral hypothalamus rather than an effect on metabolic rate.
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Mechanisms of Action
• Releases monoamines at synapses in the brain and spinal cord.
• Inhibits neuronal uptake of monoamine
• Antagonist at certain adrenoreceptors
• May inhibit monoamine oxidase.
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Adverse Effects• CNS: Euphoria, dizziness, tremor,
irritability, insomnia, Convulsion (at higher doses), hyperthermia and coma
• C.V. Cardiac stimulation leads to headache, palpitations, cardiac arrhythmias, anginal pain
• Other: Weight loss, Psychotic Reaction which are often misdiagnosed as schizophrenia.
• Addiction - including psychic dependence, tolerance and physical dependence.
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• Drug Interactions:– Tricyclic antidepressant– Antihypertensive Agents– Foods high in tyramine content
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• Amphetamine-like Drugs or ADHD and Narcolepsy – Given to increase a child’s attention span and
cognitive performance and decrease impulsiveness, hyperactivity and restlessness
Prototype:– Methylphenidate(Ritalin)– Dexmethypendate (Focalin)– Pemoline (Cylert)– Modafinil(Provigil)- drug for nacolepsy which
increases the amount of time that clients feel awake
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Side Effects:anorexia, vomiting, diarrhea, insomnia, dizziness, nervousness, restlessness, irritability
Adverse reaction:tachycardia, growth suppression, palpitations, transient loss of weight in children, and increased hyperactivity
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Nursing considerations:
• Monitor V/S. report irregularities
• Record height, weight, and growth of children
• Observe for withdrawal symptoms (N and V, weakness, and headache)
• Monitor for side effects
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Nursing considerations• Instruct client to take drug with meals• Avoid alcohol consumption • Encourage use of sugarless gum to relieve
dryness of mouth • Monitor weight twice a week • Advise not to drive and use hazardous
equipments when experiencing palpitation, nervousness, tremors
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• Instruct client not to discontinue the drug abruptly
• Advise not to eat foods with caffeine • Instruct to eat nutritious food because
drug may cause anorexic effect • Teach to report drug side effects such as
tachycardia and palpitations
Nursing considerations
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CNS Depressants
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CNS Depressants: Classification
They are classified according to their pharmacological action into:
1- Sedative – hypnotics2- Anaesthetics
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Sedative
-Hypnot
ics
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• Sedation–Mildest form of CNS depression
–Diminishes physical and mental responses at lower dosages of certain CNS depressants but does not affect consciousness
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Sleep Definition: Physiological depression of consciousnessSleep cycle:Starts with latency period → NREM → REM →
cycles of NREM alternate with REM (about 4 cycles)
NREM REM- Non rapid eye movement- Lasts for 90 min.- Thinking
- Rapid eye movement- Lasts for 20 min.- Dreaming
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I- Sedative - HypnoticsDefinitions
Sedatives:Drugs which calm the patient & cause sedation and in large
doses cause sleep
Hypnotics:Drugs which induce sleep that resembles the natural sleep
Ex. Barbiturates
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Sedative HypnoticsMechanism of Action• The GABA receptor is a pentameric structure that
forms a Cl- channel.
• The receptor complex includes distinct binding sites for benzodiazepines, barbiturates and GABA-like substances.
• GABA transmission exerts an inhibitory effect on norepinephrine (NE), dopamine (DA), serotonin (5-HT), and acetylcholine (ACh) pathways.
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Sedative – hypnotics: Classification
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BarbituratesMOA:They have GABA like action → ↑ opening time
of chloride channels → ↑conductance of chloride ions → hyperpolarization
Classification:1-Long-acting2-Intermediate-acting3-Short acting4-Ultrashort acting
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• Barbiturates – Prototype:
• Short acting: pentobarbital sodium(Nembutal sodium) – for sedation, sleep, or preanesthetic
• Intermediate acting: amobarbital sodium(Amytal sodium)- sedative and short term hypnotic, to control acute convulsive episodes, and for insomia
• Long acting: phenobarbital and mephobarbital-used to control seizures
• Ultrashort-acting: thiopental sodium- used as a general anesthetic
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Nursing Responsibilities:
• Recognize that continued use of barbiturate might result in drug abuse
• Monitor V/S, esp. RR and BP• Raise side rails• Check for rashes• Administer phenobarbital IV at a rate of
less than 50mg/min. do not mix with other medications. If to be given IM, use large muscle such as the gluteus max
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Client teaching • Teach client the use on non pharmacological
ways to induce sleep----enjoying a warm bath, listening to music, drinking warm fluids, and avoiding drinks with caffeine 6hrs before bedtime
• Instruct to avoid alcohol and antidepressants, antipsychotics, and narcotic drugs----respiratory depression
• Avoid taking herbs• Advise not to drive or operate a machinery• Instruct to take 30mins before bedtime
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Benzodiazepines • Can suppress stage 4 of NREM sleep, which may result
in vivid dreams or nightmares and can delay REM sleep. • Effective for sleep disorders for several weeks longer
than other sedative-hypnotics but should not be longer than 3-4 weeks as a hypnotic to prevent REM rebound
Prototype: Alprazolam(Xanax)- for alleviating anxiety that may cause
sleeplessnessEstazolam(ProSom)- for treatment of insomia. Decreases
the frequency of nocturnal wakefulnessLorazepam(Ativan)-used as a pre operative sedative and
to reduce anxiety
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Nonbenzodiazepines used for short term treatment of insomia Well absorbed PO, onset 7-27 minutes
MOA: depression of the CNS, neurotransmitter inhibition
Prototype: zolpidem(Ambien)
S/E: drowsiness, lethargy, hangover, irritability, dizziness, anxiety
Adverse reactions: tolerance, physiologic dependence
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• Nursing responsibilities: – Monitor V/S. check for respiratory depression– Raise side rails– Observe for side effects (hangover, light-
headedness, dizziness, or confusion) – Teach non pharmacological ways to induce
sleep – Suggest to urinate before taking sedative
hypnotics to prevent sleep disruption – Instruct to avoid alcohol and antidepressants,
antipsychotics, and narcotic drugs----respiratory depression
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Anaesthetics Definition:Drugs which cause
unconsciousness & generalized loss of pain sensation, thus allow surgical procedures to be carried out
Classified as general and local Ex. thiopental (IV) , halothane
(inhalation)
MOA:Interfering with propagation of
nerve impulses by interfering with electrolytes movement through the cell membrane
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General anesthesia• Is a reversible loss of consciousness induced by
inhibiting neuronal impulses in several areas of the central nervous system
• General anesthetics are agents that block the pain stimulus at the cortex
Produces a state of the ff: Analgesia Amnesia Unconsciousness characterized by loss of reflexes and
muscle tone
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Local anesthesia• Injection of a solution containing anesthetic
into the tissues at the planned incision site.• Briefly disrupts sensory nerve impulse
transmission form a specific body area or region.
Types of Local anesthesia1. Topical anesthesia – topical agents are
applied directly to the area of skin or mucous membrane surfaced to be anesthetized
2. Local infiltration – is the injection of an anesthetic agent directly into the tissue around an incision, wound, or lesion.
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Purposes of Anesthesia• To produce muscle relaxation • To produce analgesia• To produce artificial sleep or to cause loss
of consciousness• To block transmission of nerve impulses• To suppress reflexes
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• Nursing responsibilities: – Monitor client’s postoperative state of
sensorium. – Check preoperative and postoperative urine
output– Record V/S after induction of anesthesia----
may result to hypotension and respiratory distress
– Administer an analgesic or a narcotic-analgesic with caution until client fully recovers from the anesthetic