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

E1- Local Anesthetics and Muscle Relaxants Flashcards

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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
How does nerve conduction velocity affect anesthetic action?
The faster the conduction velocity, the less sensitive the fiber (motor fibers are less sensitive than pain fibers)
26
What is the order of sensitivity of nerves?
Sympathetic > sensory (pain) > touch > motor
27
What are cardiovascular SE of LAs? (3)
Arrhythmias Vasodilation Hypotension
28
What are CNS SE of LAs? (7)
``` Sedation Visual/auditory disturbances Circumoral numbness Nystagmus Muscle twitching Convulsions Death ```
29
What metabolite of ESTERs may cause hypersensitivity?
PABA
30
What AMIDE has the greatest cardiac toxicity?
Bupivacaine
31
What LAs may cause methemoglobinemia? | How is it revered?
Prilocaine and Benzocaine | Methylene blue
32
What LA can cause transient neurological symptoms?
Lidocaine for spinal anesthesia
33
What are the ester drugs? (4)
Procaine Tetracaine Benzocaine Cocaine
34
What is procaine used for? (2)
Infiltration anesthesia | Diagnostic nerve blocks
35
Is Tetracaine or Procaine more potent and toxic?
Tatracaine
36
What are the uses of Tetracaine?
``` Ophthalmological use Spinal anesthesia (combined with 10% dextrose/solution is denser than CSF- Hyperbaric) ```
37
How is Benzocaine administered?
Topical only
38
What is Benzocaine used for?
Sunburns, minor burns, pruritus
39
What are the uses of cocaine?
``` Mucous membranes typically around the upper respiratory tract Reduce bleeding (dental) ```
40
What are the uses of lidocaine (amide)?
Preferred for infiltration blocks and epidural anesthesia NOT spinal blocks (risk of TNS)
41
Which amide has the highest rate of clearance?
Prilocaine
42
What are contraindications of Prilocaine?
Cardiac or respiratory disease
43
What is the use of Prilocaine?
Limited use in denistry
44
What is the use of Bupivacaine? (4)
Preferred epidural during labor Post-operative pain control Spinal anesthesia Infiltration blocks
45
What is the S-enantiomer of Bupivacaine?
Ropivacaine
46
What is the difference between Bupivacaine and Ropivacaine?
Ropivacaine is less lipid soluble and cleared more rapidly than Bupivacaine (less cardio toxic)
47
What are the uses of Ropivacaine?
Peripheral and epidural blocks (Bupivacaine is preferred b/c of its differential block)
48
What amide has intermediate duration of action and is preferred for peripheral nerve blocks?
Mepivacaine
49
Which AMIDE has an additional ester group which subjects it to metabolism by plasma esterases?
Articaine
50
What is the use of Articaine?
Dental medicine (large therapeutic window and low potential for systemic toxicity)
51
What is a SE of Articaine?
Persistent paraesthasias
52
What is the use of Dibucaine?
Topical (in the US) | Dibucaine number test (measure butyrylcholinesterase activity)
53
What are the centrally acting muscle relaxants (spasmolytics)?
“Brilliant Cops Detained Trump” - Baclofen - Cyclobenzaprine - Diazepam - Tizanidine
54
What are the direct acting muscle relaxants (spasmolytics)? -work at NMJ
Dantrolene | Botulinum Toxin
55
What is the MOA of Diazepam?
Acts on the GABA receptor to facilitate GABA-mediated presynaptic inhibition in the spinal cord
56
What are the uses of Diazepam? (4)
Alcohol/BZ withdrawal Status Epilepticus Local muscle trauma Adjunct for chronic spasticity
57
What is the MOA of Baclofen?
Agonist at GABA receptors - Stimulation opens K+ channels --> hyperpolarizes - Presynaptic inhibition of Ca2+ influx --> decreases transmitter release
58
What is the MOA of Tizanidine?
Alpha2 receptor agonist (pre and post synaptic inhibition)
59
What are the uses of Tizanidine?
Chronic and acute muscle spasms
60
What is the MOA of Dantrolene?
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
What are the uses of Danrolene? (2)
Neuroleptic malignant syndrome | Malignant hyperthermia
62
What is the MOA of Botulinum Toxin?
Inhibits ACh release from nerve at the NMJ
63
What are the uses of Botulinum Toxin?
Injected locally to control muscle spasm following stroke
64
What 2 drugs can be used for acute local muscle spasms?
Cyclobenzaprine | Carisoprodol

Pharmacology 3 (10 decks)

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