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CHAPTER 12 Central Nervous System Depressants and Muscle Relaxants

CHAPTER 12 Central Nervous System Depressants and Muscle Relaxants . CNS Depressants . Sedatives or Hypnotics. CNS Depressants . Sedatives Drugs that have an inhibitory effect on the CNS to the degree that they reduce: Nervousness Excitability Irritability without causing sleep.

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CHAPTER 12 Central Nervous System Depressants and Muscle Relaxants

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  1. CHAPTER 12Central Nervous System Depressants and Muscle Relaxants Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  2. CNS Depressants Sedatives or Hypnotics Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  3. CNS Depressants Sedatives • Drugs that have an inhibitory effect on the CNS to the degree that they reduce: • Nervousness • Excitability • Irritability without causing sleep Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  4. CNS Depressants (cont'd) Hypnotics • Calm or soothe the CNS to the point that they cause sleep • A sedative can become a hypnotic if it is given in large enough doses Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  5. CNS Depressants (cont'd) Sedative-hypnotics—dose dependent • At low doses, calm or soothe the CNS without inducing sleep • At high doses, calm or soothe the CNS to the point of causing sleep Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  6. Sleep • Normal sleep is cyclic and repetitive • A sleeping person is unaware of sensory stimuli within the immediate environment • Rapid eye movement (REM) • Non–rapid eye movement (non-REM) • Sleep stages Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  7. Table 12-2 Stages of Sleep Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  8. Sedative-Hypnotics: Barbiturates • First introduced in 1903; standard agents for insomnia and sedation • Habit forming • Only a handful commonly used today due in part to the safety and efficacy of benzodiazepines Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  9. Barbiturates: Four Categories • Ultrashort • mephobexital, thiamylal, thiopental • Short • pentobarbital, secobarbital • Intermediate • butabarbital • Long • phenobarbital, mephobarbital Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  10. Therapeutic Index • Dosage range within which the drug is effective but above which is rapidly toxic • Barbiturates have a very narrow therapeutic index Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  11. Table 12-3 Barbiturates: Onset and Duration Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  12. Barbiturates: Mechanism of Action • Site of action • Brainstem (reticular formation) • By inhibiting GABA, nerve impulses traveling in the cerebral cortex are also inhibited Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  13. Barbiturates: Drug Effects • Low doses: sedative effects • High doses: hypnotic effects (also lowers respiratory rate) • Notorious enzyme inducers • Stimulate liver enzymes that cause the metabolism or breakdown of many drugs Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  14. Barbiturates: Indications • Hypnotic • Sedative • Anticonvulsant • Anesthesia for surgical procedures Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  15. Barbiturates: Side Effects Body SystemEffects CNS Drowsiness, lethargy, vertigo, mental depression, coma Respiratory Respiratory depression, apnea, bronchospasms, cough Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  16. Barbiturates: Side Effects (cont'd) Body SystemEffects GI Nausea, vomiting, diarrhea constipation Other Agranulocytosis, vasodilation, hypotension, Stevens-Johnson syndrome Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  17. Barbiturates: Side Effects (cont'd) • Reduce REM sleep, resulting in: • Agitation • Inability to deal with normal stress Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  18. Barbiturates:Toxicity and Overdose • Overdose frequently leads to respiratory depression, and subsequently, respiratory arrest • Overdose produces CNS depression (sleep to coma and death) • Can be therapeutic • Anesthesia induction • Uncontrollable seizures: “phenobarbital coma” Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  19. Barbiturates:Drug Interactions • Additive effects • ETOH, antihistamines, benzodiazepines, narcotics, tranquilizers • Inhibited metabolism • MAOIs will prolong effects of barbiturates • Increased metabolism • Reduces anticoagulant response, leading to possible clot formation Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  20. Common Barbiturates • butabarbital (Butisol) • pentobarbital (Nembutol) • phenobarbital (Luminal) • secobarbital (Seconal) Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  21. CNS Depressants: Benzodiazepines Most frequently prescribed sedative-hypnotics • Most commonly prescribed drug classes • Favorable side effect profiles • Efficacy • Safety Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  22. Benzodiazepines: Classification • Classified as either: • Sedative-hypnotic • anxiolytic (medication that relieves anxiety) Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  23. Benzodiazepines:Sedative-Hypnotic Types • Long acting • estazolam (Prosom), quazepam (Doral) • Short acting • flurazepam (Dalmane), temazepam (Restoril) • triazolam (Halcion) Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  24. CNS Depressants: Nonbenzodiazepine Hypnotics Zalepion (Sonata) and zolpidem (Ambien) • Share many characteristics of benzodiazepines Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  25. 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 Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  26. Benzodiazepines:Drug Effects • Calming effect on the CNS • Useful in controlling agitation and anxiety • Reduce excessive sensory stimulation, inducing sleep • Induce skeletal muscle relaxation Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  27. Benzodiazepines:Indications • Sedation • Sleep induction • Skeletal muscle relaxation • Anxiety relief • Treatment of alcohol withdrawal Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  28. Benzodiazepines:Indications (cont'd) • Agitation • Depression • Epilepsy • Balanced anesthesia Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  29. Benzodiazepines: Side Effects Mild and infrequent • Headache • Drowsiness • Dizziness • Vertigo • Lethargy • Paradoxical excitement (nervousness) • “Hangover effect” Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  30. CNS Depressants: Nursing Implications • Before beginning therapy, perform a thorough history regarding allergies, use of other medications, health history, and medical history • Obtain baseline vital signs and I&O, including supine and erect BPs • Assess for potential disorders or conditions that may be contraindications, and for potential drug interactions Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  31. Nursing Implications • Give 15 to 30 minutes before bedtime for maximum effectiveness in inducing sleep • Most benzodiazepines (except flurazepam) cause REM rebound and a tired feeling the next day; use with caution in the elderly • Patients should be instructed to avoid alcohol and other CNS depressants Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  32. Nursing Implications • Check with physician before taking any other medications, including OTC medications • It may take 2 to 3 weeks to notice improved sleep when taking barbiturates • Rebound insomnia may occur for a few nights after a 3- to 4-week regimen has been discontinued Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  33. Nursing Implications • Safety is important • Keep side rails up or use bed alarms • Do not permit smoking • Assist patient with ambulation (especially the elderly) • Keep call light within reach • Monitor for side effects Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  34. Nursing Implications • Monitor for therapeutic effects • Increased ability to sleep at night • Fewer awakenings • Shorter sleep-induction time • Few side effects, such as hangover effects • Improved sense of well-being because of improved sleep Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  35. 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 • Acts directly on skeletal muscle • Closely resembles GABA Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  36. Muscle Relaxants: Indications • Relief of painful musculoskeletal conditions • Muscle spasms • Management of spasticity of severe chronic disorders • Multiple sclerosis, cerebral palsy • Work best when used along with physical therapy Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  37. Muscle Relaxants: Indications (cont'd) • dantrolene • Malignant hyperthermia crisis Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  38. Muscle Relaxants: Side Effects • Extension of effects on CNS and skeletal muscles • Euphoria • Lightheadedness • Dizziness • Drowsiness • Fatigue • Muscle weakness Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  39. Common Muscle Relaxants • baclofen (Lioresal) • cyclobenzaprine (Flexeril) • dantrolene (Dantrium) • metaxalone (Skelaxin) • tizanidine (Zanaflex) Mosby items and derived items © 2005, 2002 by Mosby, Inc.

  40. Muscle Relaxants: Nursing Implications • See others listed for CNS depressants Mosby items and derived items © 2005, 2002 by Mosby, Inc.

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