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7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
7. drugs affecting the nervous system
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7. drugs affecting the nervous system

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  • 1. Chapter 7 Drugs Affecting the Nervous System Copyright © 2011 Delmar, Cengage Learning
  • 2. Basic Anatomy and Physiology
    • Basic unit of the nervous system = neuron
      • Sensory
      • Associative
      • Motor
    • Parts of the neuron
      • Cell body
      • Dendrite
      • Axon
    • Two parts of the nervous system
      • CNS (central): brain and spinal cord
      • PNS (peripheral): cranial nerves, spinal nerves, autonomic nervous system
    Copyright © 2011 Delmar, Cengage Learning
  • 3. Autonomic Nervous System
    • Sympathetic (Adrenergic): “fight or flight”
      • Increases heart rate, respiration rate, and blood flow to muscles; decreases GI function; causes pupillary dilation
      • Preganglionic synapse: ACh; postganglionic synapse: epi or norepi
    Copyright © 2011 Delmar, Cengage Learning
  • 4. Autonomic Nervous System
    • Parasympathetic (Cholinergic): “homeostatic”
      • Brings heart rate, respiration rate, and blood flow to muscles back to normal levels; returns GI function to normal; constricts pupils to normal size
      • Pre- and postganglionic synapse: ACh
    Copyright © 2011 Delmar, Cengage Learning
  • 5. Anticonvulsants
    • help prevent seizures by suppressing the spread of abnormal electric impulses from the seizure focus to other areas of the cerebral cortex
    • All anticonvulsants are CNS depressants and may cause ataxia, drowsiness, and hepatotoxicity
    Copyright © 2011 Delmar, Cengage Learning
  • 6. Anticonvulsants
    • Barbiturates
      • CNS depressant
      • Grouped by duration of action
      • Phenobarbital, pentobarbital, primidone
    Copyright © 2011 Delmar, Cengage Learning
  • 7. Anticonvulsants
    • Benzodiazepines
      • Potentiate effects of GABA, cause muscle relaxation, relieve anxiety
      • Diazepam, lorazepam, clorazepate
    Copyright © 2011 Delmar, Cengage Learning
  • 8. Anticonvulsants
    • Potassium bromide
      • Adjunct to anticonvulsant therapy
      • Depressive effect on neuron excitability
      • Long half life; given as a loading dose
    Copyright © 2011 Delmar, Cengage Learning
  • 9. Anticonvulsants
    • Add-ons: used for refractory seizures
      • Levetiracetam
        • Dogs and cats
        • Side effects include sedation, ataxia, and anorexia
      • Zonisamide
        • Works by blocking calcium and sodium channels in the brain
        • Side effects include ataxia and sedation
    Copyright © 2011 Delmar, Cengage Learning
  • 10. Anticonvulsants
    • Add-ons: used for refractory seizures
      • Gabapentin
        • Works by inhibiting calcium channels resulting in decreased excitatory neurotransmission
        • Side effects include sedation, ataxia, and the potential for hepatotoxicity
      • Felbamate
        • Used in dogs that to control seizures
        • Side effects include hepatotoxicity, reversible blood dyscrasias, and keratoconjunctivitis sicca
    Copyright © 2011 Delmar, Cengage Learning
  • 11. Calming Agents
    • Tranquilizers: used to calm animals; reduce anxiety and aggression
    • Sedatives: used to quiet excited animals; decrease irritability and excitement
    • Anti-anxiety drugs: lessen anxiousness, but do not make animals drowsy
    Copyright © 2011 Delmar, Cengage Learning
  • 12. Calming Agents
    • Phenothiazine derivatives
      • Unknown mechanism, believed to block dopamine and alpha-1 receptors
      • Causes sedation, relieves fear and anxiety
      • Doesn’t produce analgesia
      • Side effects: hypotension, lower seizure threshold, protrusion of nictitating membrane, paraphimosis
    Copyright © 2011 Delmar, Cengage Learning
  • 13. Calming Agents
    • Butyrophenones
      • Similar to phenothiazines
      • Side effects: salivation, panting, shivering
    • Benzodiazepines
      • Anti-anxiety, produce muscle relaxation, reduce anxiousness
    • Alpha-2 agonists
      • Some analgesia, some muscle relaxation, decreased response to stimuli
      • Side effects: bradycardia and heart block
    Copyright © 2011 Delmar, Cengage Learning
  • 14. Analgesics
    • Pain is classified as:
      • Physiologic: the bodies protective mechanism to avoid tissue injury
      • Pathologic: arises from tissue injury and inflammation or from damage to nervous system
        • Can be furthered divided into nociceptive (peripheral tissue injury) or neuropathic (damage to the peripheral nerves or central nervous system)
      • Acute: arising from a sudden stimulus such as surgery
      • Chronic: persisting beyond the time normally associated with tissue injury
    Copyright © 2011 Delmar, Cengage Learning
  • 15. Analgesics
    • Signs of pain in animals
      • Change in personality
      • Abnormal vocalization
      • Licking, biting, scratching pain area
      • Change in appearance of hair coat
      • Change in posture/ambulation
      • Change in activity level
      • Change in appetite
      • Change in facial expression
      • Excessive sweating or salivation
      • Oculonasal discharge
      • Teeth grinding
      • Change in bowel movement or urination
    Copyright © 2011 Delmar, Cengage Learning
  • 16. Analgesics
    • Analgesics: drugs that relieve pain
    • Analgesics are categorized as non-narcotic (Chapter 16) or narcotic
    • Narcotic analgesics are used for moderate to severe pain
    Copyright © 2011 Delmar, Cengage Learning
  • 17. Analgesics
    • Narcotics refers to opiate (natural from opium poppy seeds) or opioid-like (synthetic)
      • Opioids produce analgesia and sedation and relieve anxiety
      • Side effects of opioids include respiratory depression and excitement if given rapidly
    Copyright © 2011 Delmar, Cengage Learning
  • 18. Opioids
    • Do not produce anesthesia; patients still respond to sound and sensation
    • Produce analgesia and sedation, and relieve anxiety
    • Side effects: respiratory depression, excitement if given too rapidly
    • Produce their effects by the action of opioid receptors
      • Mu = found in the brain
      • Kappa = found in the cerebral cortex and spinal cord
      • Sigma = found in the brain
    Copyright © 2011 Delmar, Cengage Learning
  • 19. Opioids
      • Opium
      • Morphine sulfate
      • Meperidine
      • Hydromorphone
      • Butorphanol
      • Hydrocodone
      • Fentanyl
      • Etorphine
      • Buprenorphine
      • Pentazocine
    Copyright © 2011 Delmar, Cengage Learning
  • 20. Opioid Antagonist
    • Block the binding of opioids to their receptors
    • Used to treat respiratory and CNS depression of opioid use
    • Examples include naloxone and naltrexone
    • Naloxone is a opioid antagonist used to reverse respiratory depression following narcotic overdose
      • Relatively free of side effects
    Copyright © 2011 Delmar, Cengage Learning
  • 21. Neuroleptanalgesics
      • Combination of an opioid and a tranquilizer or sedative
      • Can cause a state of CNS depression and analgesia and may or may not produce unconsciousness
      • Combination products may be prepared by veterinarian
      • Examples include acepromazine and morphine; xylazine and butorphanol
    Copyright © 2011 Delmar, Cengage Learning
  • 22. Anesthetics
      • Anesthesia means without sensation
      • Anesthetics interfere with the conduction of nerve impulses
      • Anesthetics produce loss of sensation and muscle relaxation, and may cause loss of consciousness
      • General anesthetics affect the CNS, produce loss of sensation with partial or complete loss of consciousness
      • Local anesthetics block nerve transmission in the area of application with no loss of consciousness
    Copyright © 2011 Delmar, Cengage Learning
  • 23. Local Anesthetics
      • Block pain at the site of administration or application in the PNS and spinal cord
      • May be used as nerve blocks, aid in endotracheal tube placement, and ease skin irritation
      • Applied topically to mucous membranes and the cornea by infiltration of a wound or joint, by IV, and around nervous tissue
      • Examples include lidocaine, proparacaine, tetracaine, mepivacaine, bupivacaine
    Copyright © 2011 Delmar, Cengage Learning
  • 24. General Anesthetics
    • Injectable general anesthetics:
      • Barbiturates: CNS depressants derived from barbituric acid. Used mainly as anticonvulsants, anesthetics, and euthanasia solutions
      • Side effects: potent cardiovascular and respiratory depression
      • May be long-acting, short-acting, or ultra-short acting
      • May vary in structure and be classified as an oxybarbiturate or thiobarbiturate
      • Examples: phenobarbital, pentobarbital, thiopental, methohexital
    Copyright © 2011 Delmar, Cengage Learning
  • 25. General Anesthetics
    • Injectable general anesthetics (cont.):
      • Dissociatives: belong to the cyclohexamine family
      • Cause muscle rigidity (catalepsy), amnesia, and mild analgesia
      • Work by altering neurotransmitter activity
      • Used for restraint, diagnostic procedures, and minor surgical procedures
      • Side effects: cardiac stimulation, respiratory depression, and exaggerated reflexes
      • Examples include ketamine and tiletamine
    Copyright © 2011 Delmar, Cengage Learning
  • 26. General Anesthetics
    • Injectable general anesthetics (cont.):
      • Miscellaneous:
        • Guaifenesin: skeletal muscle relaxant used in combination with an anesthetic drug to induce general anesthesia in horses
        • Propofol: short-acting injectable anesthetic agent that produces rapid and smooth induction when given IV (lasts 2 – 5 minutes)
          • Side effects include cardiac arrhythmias and apnea
    Copyright © 2011 Delmar, Cengage Learning
  • 27. General Anesthetics/Analgesics
    • Inhalant general anesthetics: inhalant anesthetics are halogenated hydrocarbons
      • Halothane:
        • Nonflammatory, inhalant anesthetic administered via a precision vaporizer
        • Can cause hepatic problems, malignant hyperthermia, cardiac problems, and tachypnea
        • Contraindicated in cases of gastric dilatation, pneumothorax, and twisted intestines
        • Leave animals on 100% oxygen following surgery to prevent diffusion hypoxia
    Copyright © 2011 Delmar, Cengage Learning
  • 28. General Anesthetics/Analgesics
    • Inhalant general anesthetics (cont.):
      • Isoflurane:
        • Nonflammatory, inhalant anesthetic administered via a precision vaporizer
        • Causes rapid induction of anesthesia and short recoveries following anesthetic procedures
        • Does not cause the cardiac arrhythmia problems of halothane
        • Vigilant monitoring is needed because the animal can change anesthetic planes quickly
        • Masking of animals with isoflurane is difficult because it irritates the respiratory system
        • Side effects include respiratory depression and malignant hyperthermia
    Copyright © 2011 Delmar, Cengage Learning
  • 29. General Anesthetics/Analgesics
    • Inhalant general anesthetics (cont.):
      • Isomers of isoflurane:
        • Nonflammable and have fewer cardiovascular side effects than other inhalants
        • Quickly enter the bloodstream and escape to the brain, making them good for mask inductions
        • Examples:
          • Enflurane: increases intracranial pressure (do not use if animal has seizure history)
          • Desflurane: cannot be delivered by standard vaporizers and can reduce blood pressure
          • Sevoflurane: profound respiratory depressant; close monitoring is needed
    Copyright © 2011 Delmar, Cengage Learning
  • 30. General Anesthetics/Analgesics
    • Inhalant general anesthetics (cont.):
      • Sevoflurane:
        • A non-flammable inhalant anesthetic
        • The main isomer of isoflurane
        • Produces rapid induction and rapid recoveries
        • Produces fewer cardiovascular side effects than the other inhalant anesthetics
        • Quickly enters the bloodstream and escapes to the brain, also is eliminated quickly from the body
        • Has low tissue solubility, resulting in rapid elimination of the drug by the body
    Copyright © 2011 Delmar, Cengage Learning
  • 31. General Anesthetics/Analgesics
    • Inhalant general analgesics (cont.):
      • Nitrous oxide:
        • Inhalant analgesic that diffuses rapidly throughout the body
        • Can enter gas-filled body compartments (increases pressure in these compartments)
        • Contraindicated in cases of gastric dilatation, pneumothorax, and twisted intestines
        • Leave animals on 100% oxygen following surgery to prevent diffusion hypoxia
    Copyright © 2011 Delmar, Cengage Learning
  • 32. CNS Stimulants
    • Reverse CNS depression caused by CNS depressants
      • Doxapram: stimulates brainstem to increase respiration in animals with apnea or bradypnea; commonly used when animals have C-sections
      • Methylxanthines: bronchodilators that have adverse effect of CNS stimulation; include caffeine, theophylline, and aminophylline; side effects include gastrointestinal irritation and bronchodilation
    Copyright © 2011 Delmar, Cengage Learning
  • 33. Euthanasia Solutions
    • Used to humanely end an animal’s life
    • Usually contain pentobarbital
    • When pentobarbital is the only narcotic agent present, it is a C-II controlled substance
    • When pentobarbital is in combination with other agents, it is a C-III controlled substance
    Copyright © 2011 Delmar, Cengage Learning
  • 34. Autonomic Nervous System Drugs
    • Autonomic nervous system drugs work either by acting like neurotransmitters or by interfering with neurotransmitter release
    • Two groups of drugs affect the parasympathetic nervous system
    • Two groups of drugs affect the sympathetic nervous system
    Copyright © 2011 Delmar, Cengage Learning
  • 35. Cholinergic Drugs
    • Mimic the action of the parasympathetic nervous system (refer to Table 7-5 in your textbook)
    • Examples include bethanechol, metoclopramide, pilocarpine, edrophonium, neostigmine, demecarium, and organophosphates
    Copyright © 2011 Delmar, Cengage Learning
  • 36. Anticholinergic Drugs
    • Inhibit the actions of acetylcholine by occupying the acetylcholine receptors (refer to Table 7-6 in your textbook)
    • Examples include atropine, glycopyrrolate, aminopentamide, and propantheline
    Copyright © 2011 Delmar, Cengage Learning
  • 37. Adrenergic Drugs
    • Simulate the action of the sympathetic nervous system (refer to Table 7-7 in your textbook)
    • Side effects include tachycardia, hypertension, and cardiac arrhythmias
    • Examples include epinephrine, norepinephrine, isoproterenol, dopamine, dobutamine, phenylpropanolamine, isoetharine, albuterol, terbutaline, ephedrine, and xylazine
    Copyright © 2011 Delmar, Cengage Learning
  • 38. Adrenergic Blocking Agents
    • Block the effects of the adrenergic neurotransmitters (refer to Table 7-7 in your textbook)
    • Examples of alpha-blockers include phenoxybenzamine, prazosin, and yohimbine
    • Examples of beta-blockers include propranolol, metoprolol, and timolol
    Copyright © 2011 Delmar, Cengage Learning

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