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Central Nervous System Agents

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  • 1. Central Nervous System Agents Ma. Tosca Cybil A. Torres, RN, MAN
  • 2. CNS Stimulants
  • 3. 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
  • 4. Behavioral Manifestations of CNS Stimulation • mild elevation in alertness, decrease in drowsiness and lessening of fatigue (Analeptic Effect) • increased nervousness and anxiety - convulsions.
  • 5. Molecular Basis of CNS Stimulation Imbalance between inhibitory and excitatory processes 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)
  • 6. Classification of CNS Stimulants • Analeptic Stimulants – Respiratory Stimulants – Convulsants • Psychomotor Stimulant – Sympathomimetics or Adrenergic CNS Stimulants • Methylxanthines
  • 7. 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
  • 8. Respiratory CNS Stimulants • 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
  • 9. 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
  • 10. Preventive Treatment for migraine 1. Beta adrenergic blockers 2. Anticonvulsants- Valproic acid (Depakote) 3. Tricyclic antidepressants- amitriptyline (Elavil)
  • 11. 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
  • 12. • 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
  • 13. • Amphetamines – Stimulates the release of norepinephrine and dopamine from the brain and SNS. – Can cause euphoria and alertness
  • 14. 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
  • 15. • 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
  • 16. • 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.
  • 17. 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.
  • 18. • 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.
  • 19. 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.
  • 20. 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.
  • 21. • Drug Interactions: – Tricyclic antidepressant – Antihypertensive Agents – Foods high in tyramine content
  • 22. • 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
  • 23. 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
  • 24. 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
  • 25. 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
  • 26. Nursing considerations • 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
  • 27. CNS Depressa nts
  • 28. CNS Depressants: Classification They are classified according to their pharmacological action into: 1- Sedative – hypnotics 2- Anaesthetics
  • 29. e - Hypnoti cs
  • 30. • Sedation –Mildest form of CNS depression –Diminishes physical and mental responses at lower dosages of certain CNS depressants but does not affect consciousness
  • 31. ep Definition: Physiological depression of consciousness Sleep cycle: Starts with latency period → NREM → REM → cycles of NREM alternate with REM (about 4 cycles) NREM REM - Non rapid eye movement - Rapid eye movement - Lasts for 90 min. - Lasts for 20 min. - Thinking - Dreaming
  • 32. I- Sedative - Hypnotics Definitions 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
  • 33. Sedative Hypnotics Mechanism 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.
  • 34. Sedative – hypnotics: Classification Sedative-hypnotics Barbiturates Non-barbiturates 1-Long acting (12-24 hr) Ex. Phenobarbital Benzodiazepines Non- benzodiazepine 2-Intermediate acting (8-12hr) Ex. Amobarbital 3-Short acting (4-8 hr) Ex. Pentobarbital 4-Ultrashort acting (0.5-1hr) Ex. Thiopental
  • 35. Barbiturates MOA: They have GABA like action → ↑ opening time of chloride channels → ↑conductance of chloride ions → hyperpolarization Classification: 1-Long-acting 2-Intermediate-acting 3-Short acting 4-Ultrashort acting
  • 36. • 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
  • 37. 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
  • 38. 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
  • 39. 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 sleeplessness Estazolam(ProSom)- for treatment of insomia. Decreases the frequency of nocturnal wakefulness Lorazepam(Ativan)-used as a pre operative sedative and to reduce anxiety
  • 40. 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, dizzine ss, anxiety Adverse reactions: tolerance, physiologic dependence
  • 41. • 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
  • 42. 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
  • 43. 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
  • 44. 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 anesthesia 1. 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.
  • 45. 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
  • 46. • 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