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Pharmacology 3 > E1- Local Anesthetics and Muscle Relaxants > Flashcards

E1- Local Anesthetics and Muscle Relaxants Flashcards

1
Q

Do esters or amids typically have shorter duration of action and increased systemic toxicity?

A

Esters

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2
Q

LAs are weak acids/bases?

At physiologic pH, LA are predominantly ionized/nonionized?

A 
Weak bases (pKa 7.5-9)
Ionized
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3
Q

Which form of LAs crosses the cell membrane?

A

Non-ionized

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4
Q

Which form of LAs binds to the intracellular binding site of the Na+ channel?

A

Ionized

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5
Q

What LA is an exception to the ionization rules?

A

Benzocaine (pka 3.5)- always in the non-ionized form; topical application only

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6
Q

What is the secondary pathway for LAs?

A

Hydrophobic pathway: non-ionized enters the cell membrane and becomes ionized within the membrane; the ionized form then binds to the Na+ channel

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7
Q

The closer the pka is to physiological pH (7.4), the higher the concentration in the ____ form.
Faster/slower membrane transport?
Faster/slower onset of action

A

Non-ionized
Faster membrane transport
Faster onset of action

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8
Q

Does infection/inflammation lead to faster/slower onset of action?

A 
Slower onset (need more drug)
-Lower pH --> higher concentration in the ionized form --> membrane transport decreases
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9
Q

Does bicarbinate lead to faster/slower onset of action?

A

Faster onset

Higher pH –> higher concentration in the non-ionized form –> membrane transport increases

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10
Q

What is the MOA of LAs?

A

Block Na+ channels and inhibit neuronal firing

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11
Q

LAs have high affinity for what type of channels?

LAs have low affinity for what type of channels?

A

High affinity- active (open) and inactivated states

Low affinity- resting state (closed)

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12
Q

What is the effect on elevated Ca2+ on LAs?

A

Hyperpolarize membrane; more channels in resting state –> block is diminished

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13
Q

What is the effect on elevated K+ on LAs?

A

Depolarize membrane; more channels in inactivated state –> block is enhanced

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14
Q

Which LA has a short duration of action?

A

Procaine

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15
Q

Which LAs have an intermediate duration of action?

A

Cocaine
Mepivacaine
Lidocaine

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16
Q

Which LAs have a long duration of action?

A

Tetracaine
Bupivacaine
Ropivacaine

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17
Q

What is the effect of Epinephrine on LAs?

A

Vasoconstricting agent

  • Decreases diffusion of drug
  • Prolongs duration of action
  • Decreases systemic absorption
  • Decreases risk of systemic toxicity
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18
Q

Should Amides or Esters be avoided in pts with hepatic disease? Why?

A

Amides

Metabolized in the liver by CYP450s

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19
Q

How are Esters metabolized?

A

Rapidly metabolized by butyrylchoinesterases in the plasma

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20
Q

What LA preferentially blocks sensory neurons?

A

Bupivacaine

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21
Q

What AMIDE preferentially blocks motor neurons? (inverse differential block)

A

Etidocaine

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22
Q

How does anatomic arrangement affect anesthetic action?

A

Effect hits proximal fibers and proceeds to more distal fibers within nerve bundle

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23
Q

How does nerve diameter affect anesthetic action?

A

Smaller diameter fibers are more sensitive

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24
Q

How does degree of nerve myelination affect anesthetic action?

A

Myelinated fibers are less sensitive than unmyelinated fibers

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25
Q

How does nerve conduction velocity affect anesthetic action?

A

The faster the conduction velocity, the less sensitive the fiber (motor fibers are less sensitive than pain fibers)

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26
Q

What is the order of sensitivity of nerves?

A

Sympathetic > sensory (pain) > touch > motor

27
Q

What are cardiovascular SE of LAs? (3)

A

Arrhythmias
Vasodilation
Hypotension

28
Q

What are CNS SE of LAs? (7)

A 
Sedation
Visual/auditory disturbances
Circumoral numbness
Nystagmus
Muscle twitching
Convulsions
Death
29
Q

What metabolite of ESTERs may cause hypersensitivity?

A

PABA

30
Q

What AMIDE has the greatest cardiac toxicity?

A

Bupivacaine

31
Q

What LAs may cause methemoglobinemia?

How is it revered?

A

Prilocaine and Benzocaine

Methylene blue

32
Q

What LA can cause transient neurological symptoms?

A

Lidocaine for spinal anesthesia

33
Q

What are the ester drugs? (4)

A

Procaine
Tetracaine
Benzocaine
Cocaine

34
Q

What is procaine used for? (2)

A

Infiltration anesthesia

Diagnostic nerve blocks

35
Q

Is Tetracaine or Procaine more potent and toxic?

A

Tatracaine

36
Q

What are the uses of Tetracaine?

A 
Ophthalmological use
Spinal anesthesia (combined with 10% dextrose/solution is denser than CSF- Hyperbaric)
37
Q

How is Benzocaine administered?

A

Topical only

38
Q

What is Benzocaine used for?

A

Sunburns, minor burns, pruritus

39
Q

What are the uses of cocaine?

A 
Mucous membranes typically around the upper respiratory tract
Reduce bleeding (dental)
40
Q

What are the uses of lidocaine (amide)?

A

Preferred for infiltration blocks and epidural anesthesia

NOT spinal blocks (risk of TNS)

41
Q

Which amide has the highest rate of clearance?

A

Prilocaine

42
Q

What are contraindications of Prilocaine?

A

Cardiac or respiratory disease

43
Q

What is the use of Prilocaine?

A

Limited use in denistry

44
Q

What is the use of Bupivacaine? (4)

A

Preferred epidural during labor
Post-operative pain control
Spinal anesthesia
Infiltration blocks

45
Q

What is the S-enantiomer of Bupivacaine?

A

Ropivacaine

46
Q

What is the difference between Bupivacaine and Ropivacaine?

A

Ropivacaine is less lipid soluble and cleared more rapidly than Bupivacaine (less cardio toxic)

47
Q

What are the uses of Ropivacaine?

A

Peripheral and epidural blocks (Bupivacaine is preferred b/c of its differential block)

48
Q

What amide has intermediate duration of action and is preferred for peripheral nerve blocks?

A

Mepivacaine

49
Q

Which AMIDE has an additional ester group which subjects it to metabolism by plasma esterases?

A

Articaine

50
Q

What is the use of Articaine?

A

Dental medicine (large therapeutic window and low potential for systemic toxicity)

51
Q

What is a SE of Articaine?

A

Persistent paraesthasias

52
Q

What is the use of Dibucaine?

A

Topical (in the US)

Dibucaine number test (measure butyrylcholinesterase activity)

53
Q

What are the centrally acting muscle relaxants (spasmolytics)?

A

“Brilliant Cops Detained Trump”

  • Baclofen
  • Cyclobenzaprine
  • Diazepam
  • Tizanidine
54
Q

What are the direct acting muscle relaxants (spasmolytics)? -work at NMJ

A

Dantrolene

Botulinum Toxin

55
Q

What is the MOA of Diazepam?

A

Acts on the GABA receptor to facilitate GABA-mediated presynaptic inhibition in the spinal cord

56
Q

What are the uses of Diazepam? (4)

A

Alcohol/BZ withdrawal
Status Epilepticus
Local muscle trauma
Adjunct for chronic spasticity

57
Q

What is the MOA of Baclofen?

A

Agonist at GABA receptors

  • Stimulation opens K+ channels –> hyperpolarizes
  • Presynaptic inhibition of Ca2+ influx –> decreases transmitter release
58
Q

What is the MOA of Tizanidine?

A

Alpha2 receptor agonist (pre and post synaptic inhibition)

59
Q

What are the uses of Tizanidine?

A

Chronic and acute muscle spasms

60
Q

What is the MOA of Dantrolene?

A

Inhibits Ca2+ release from the SR by blocking the ryanodine receptor 1 (RyT1) channel
(Interferes with excitation-contraction coupling of actin/myosin in SKELETAL muscle)

61
Q

What are the uses of Danrolene? (2)

A

Neuroleptic malignant syndrome

Malignant hyperthermia

62
Q

What is the MOA of Botulinum Toxin?

A

Inhibits ACh release from nerve at the NMJ

63
Q

What are the uses of Botulinum Toxin?

A

Injected locally to control muscle spasm following stroke

64
Q

What 2 drugs can be used for acute local muscle spasms?

A

Cyclobenzaprine

Carisoprodol

Pharmacology 3 (10 decks)

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