7. drugs affecting the nervous system

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7. drugs affecting the nervous system

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

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