Pharm I, Local Anesthetics

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HLW
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74381
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Pharm I, Local Anesthetics
Updated:
2011-03-22 23:10:06
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Pharm I, Local Anesthetics
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  1. Benefits of Systemic Lidocain (3):
    • Central Analgesic Effect (Blocks Na channel in central nociceptive neurons)
    • Prokinetic (GIT)
    • Antioxident/Inflammatory modulators
  2. Used appropiately, Local Anaesthetics provide ____ analgesia
    Absolute
  3. Local Anasthetics are classified as:
    • Esters
    • Amides
  4. Most common Amide LA's (3):
    • Lidocain
    • Bupivicaine
    • Mepivicaine
  5. Most common Ester LA's:
    Tetracaine
  6. Tetracaine is often used for...
    ocular anaesthetics
  7. Ester Vs Amide LA (1/2 Life and stability):
    • Ester= unstable, 1/2 life is a few mins
    • Amides= Stable, 1/2 life is a few hours
  8. LAs are transported in the plasma, and are bound to _____& ____. The ____ is active
    • Alpha Glycoproteins
    • Albumin (minimally)
    • Unbound drug
  9. What property affects the potency of LA's
    Increasing Lipid Solubility
  10. What property affects the duration of action of LAs
    Protein Binding
  11. What property affects the rapidity of onset of LAs?
    Low pKa= Rapid onset
  12. What LA's have a rapid onset?
    • Lidocaine
    • Mepivicaine
  13. Rate of Diffusion is dependent on (4):
    • pKa of Drug
    • pH of nerve
    • Amount of LA
    • Vascular Removal
  14. Successful impulse blockade is dependent on
    • Sufficient concentration of anesthetic within and along axon
    • Na/K channel density
    • Na/K channel susceptibility
  15. As a rule of thumb, ________, the greater concentration of LA required to produce blockade
    the greater the diameter of nerve fiber
  16. Which neuron type is unmyelinated?
    C
  17. How does dosage affect an anasthetic block?
    • Rapidity of Onset
    • Intensity
    • Duration
  18. How does volume affect an anasthetic block?
    • Spread
    • Dermatomal Distribution of neural blockade
    • DOES NOt DETERMINE SPEED OF ONSET, INTENSITY, OR DURATION
  19. How does pH affect an anasthetic block?
    The closer the pKa to physiological pH, the better it penetrates the membrane
  20. How can pH of LA be alkalinized?
    Add Sodium Bicarbonate
  21. Repeated blocks can cause...
    Tachyphylaxis, especially when pH ~pKa
  22. Local Anesthetic Side Fx Occur when...
    high plasma concentrations are achieved
  23. LA plasma concentrations are determined by (6):
    • Quantity(dose)
    • Route
    • Rate of Absorption
    • Acid-Base Status
    • Rate of Metab
    • +/- Epi
  24. Lidocaine TOXIC dose, IV:
    10mg/kg
  25. Never give more than ___mg/kg Lidocaine IV
    4
  26. Bupivicaine TOXIC dose, IV:
    4mg/kg
  27. Never give more than ___mg/Kg Bupivicaine IV
    2
  28. What must be considered when combining local anaesthetics?
    Toxicity of each is additive
  29. CNS effects of LA OD (2)
    • CNS Depression
    • Followed by Agitation, Muscle Twitching and convulsions
  30. Cardiovascular Effects of LA OD (2):
    • Myocardial Depression (Bradycardia and Decreased CO)
    • Hypotension
  31. Which is harder to tx Lidocaine or Bupivacaine OD? Why?
    Bupivacaine- High binding affinity for cardiac myocytes (70x)
  32. Tx for a Local Anesth OD(5) :
    • Treat Sympotoms
    • Seizures= Valuim PRN
    • Cardiovascular= Fluids, O2, Ionotropes, Antimuscarinics if Bracycardic
  33. Precautionary steps to avoid Local Anest OD (4)
    • Caution w/ small animals
    • Double check weight
    • Diltute LA
    • Draw back before injecting
  34. Which LA has antiarrhythmic properties?
    Lidocaine
  35. Which LA is more potentially cardiotoxic?
    Bupivacaine (cardiotoxic before neurotoxic)
  36. Which LA is used for nerve blocks in horses?
    Mepivicane
  37. Less irritating alternative to Lidocaine
    Mepivicaine
  38. Benefits of using Ropivicaine over Bupivacaine (5):
    • Longer Duration
    • Less Cardiotoxic
    • Less Arrythmogenic
    • Selective for Sensory Nerve Fibers (over A alpha motor fibers)
    • Dissociates more rapidly from Na channels (less accumulation)
  39. Which LA has a longer duration of action than Lidocaine?
    Bupivicaine (2-6 hours)
  40. Which LA is a more potent alternative than Lidocaine?
    Bupivicaine
  41. Which LA can cause tachyphylaxis?
    Lidocaine
  42. What is a safer alternative to Xylocaine spray in cats?
    2% Lidocaine WITHOUT adrenaline, spray directly on Vocal Cords
  43. Rec Dosage for: Lidocaine, Mepivicaine, Bupivacaine & Ropivicaine
    • Lidocaine: 4mg/kg, but 2mg/kg is sufficient
    • Mepivacaine: 4mg/kg, but 2mg/kg is sufficient
    • Bupivacine: 2mg/kg
    • Ropivacaine: 2mg/kg

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