local anesthetic Flashcards
(78 cards)
1
Q
List the local anesthetic: Esters
A
- Procaine (Novocain®)
- Tetracaine (Pontocaine®)
- Benzocaine (Americaine®)
- Cocaine
2
Q
what drug class is Lidocaine (Xylocaine®) in
A
local anesthetics: amides
3
Q
what drug class is Prilocaine (Citanest®) in
A
local anesthetics: amides
4
Q
what drug class is Bupivacaine (Marcaine®) in
A
local anesthetics: amides
5
Q
what drug class is Mepivacaine (Carbocaine®) in
A
local anesthetics: amides
6
Q
what drug class is Ropivacaine (Naropin®) in
A
local anesthetics: amides
7
Q
what drug class is Etidocaine (Duranest®) in
A
local anesthetics: amides
8
Q
what drug class is Articaine (Septocaine®) in
A
local anesthetics: amides
9
Q
what drug class is Dibucaine (Nupercainal®) in
A
local anesthetics: amides
10
Q
what drug class is Baclofen (Lioresal®) in
A
- GABA-mimetic
- muscle relaxant
11
Q
what drug class is Diazepam (Valium®) in
A
- Benzodiazepine
12
Q
list the 4 spinal cord or brain stem sedatives
A
- Cyclobenzaprine (Flexeril®)
- Carisoprodol (Soma®)
- Metaxalone (Skelaxin®)
- Methocarbamol (Robaxin®)
13
Q
local anesthetics are broken down into what 2 groups
A
- esters
- amides
14
Q
do esters or amides have shorter duration of action? which has increased systemic toxicity?
A
- Esters have shorter duration of action
- Esters have increased systemic toxicity
15
Q
local anesthetics are acids or bases?
A
- weak bases
- pKa = 7.5-9
16
Q
What form does the local anesthetic need to be in to cross the cell membrane? what form binds to Na+ channel
A
- non-ionized (LA + H+)
- ionized (LAH+)
17
Q
the closer the pKa is the physiological pH (7.4) the higher the concentration of the local anesthetic in what form? what benefit does this have
A
- non-ionized form
- membrane transport increases -> faster onset of action
- ex: lidocaine (pKa 7.8) has a faster onset than bupivacaine (pKa 8.1)
- membrane transport increases -> faster onset of action
18
Q
what local anesthetic drug is an exception to the rule and even at a pKa of 3.5 is always in the non-ionized form ? route of administration?
A
Benzocaine
- topical application only
19
Q
how does bicarbonate affect LA transport across cell membrane
A
- makes pH more basic and may increase non-ionized drug concentrations and thus, the degree of LA transport
20
Q
MOA of local anesthestics
A
-
block Na+ channels and inhibit neuronal firing and the propagation of action potentials
- When progressively increasing concentrations of a local anesthetic are applied to a nerve fiber, the threshold for excitation increases, impulse conduction slows, the rate of rise of the action potential declines, and finally, the ability to generate an action potential is completely abolished.
21
Q
LA have high affinity for Na channels in what state
A
- high affinity for channels in the activated (open state) and inactivated state and lower affinity for channels in the resting (closed) state
- drug is more marked in rapidly firing axons than in resting fibers.
22
Q
what effect does elevated calcium have of the MOA of local anesthetics
A
- increase membrane potential; more channels are in resting state and the effect of LAs is diminished.
23
Q
what effect does elevated potassium have of the MOA of local anesthetics
A
- depolarize the membrane; more channels in inactivated state and the effect is enhanced
24
Q
duration of action of local anesthetics is dependent on
A
spent at the site of action
25
List local anesthetics with a short duration of action
* Procaine
26
List local anesthetics with a medium duration of action
* cocaine
* Mepivacaine
* Lidocaine
27
List local anesthetics with a long duration of action
* Tetracaine
* Bupivicaine
* Ropivicaine
28
toxic effects of LA are dependent on
half-life
29
how does epinephrine affect absorption of local anesthetic
* epinephrine -\> vasoconstriction
* decreases diffusion of drug
* prolongs duration of action
* decreases systemic absorption and decreases risk of systemic toxicity
30
Where are Amides LA metabolized
* Liver by CYP450
* toxicity is more likely in pts with hepatic disease or reduced hepatic blood flow
31
Where are esters LA metabolized
* rapidly metabolized by **butyrylcholinesterases** in the **plasma**
32
What is the problem with using local anesthetics for a differential block (trying to block pain)
* **block is not limited to intended site**
* also blocks motor nerves -\> motor paralysis, respiratory impairment, hypotension
* different degrees of sensory and motor nerve block in LA
* bupivacaine little action on motor
* etidocaine primarily affects motor
33
what is the order of sensitivity to LA
* **sympathetic** (blocked first) \> **sensory (pain)** \> **touch** \> **motor**
34
how does the intrinsic susceptibility of nerve fibers affect how they are blocked
* 3 factors: **diameter, degree of myelination,** and **conduction velocity**
* smaller fibers are blocked first and more sensitive
* myelinated fibers are blocked faster than unmyelinated but less sensitive
* the faster the conduction velocity, the slower the block
35
cardiovascular side effects of local anesthetics
* arrhythmias
* vasodilation
* hypotension
36
which local anesthetic has the most cardiac side effects
Bupivacaine
37
CNS effects of local anesthetics
depression of cortical inhibitory pathways
* sedation
* visual/auditory disturbances
* muscle twitching
* convulsions
38
which type of local anesthetic is more prone to cause allergic reactions
* Esters
39
Procaine is an ester or amide? long or short duration of action
* ester
* short
40
metabolic product of Procaine
* para-aminobenzoic acid (PABA)
* can cause allergic reactions
41
Use of procaine
* infiltration anesthesia
42
Tetracaine is an ester or amide? duration of action?
* ester
* long duration of actions
43
compare tetracaine and procaine in terms of toxicity
tetracaine 16 x more potent and more toxic
44
use of tetracaine
* ophthalmological use
* spinal anesthesia
45
Benzocaine is an ester or amide? route of adminstration?
* ester
* topical only
46
adverse effects of Benzocaine
methemoglobinemia
47
cocaine is an ester or amide
* ester
* used topically
48
Lidocaine is an ester or amide
* amide
49
Use of Lidocaine
* infiltration blocks
* epidural anesthesia
50
why is Lidocaine not preferred for spinal blocks
* increased risk for **Transient neurological symptoms (TNS)**
51
Prilocaine is ester or amide
* amide
52
compare the clearance of Prilocaine to the other amides
Prilocaine has the **highest rate of clearance** of the amides
53
adverse effect of Prilocaine
* methemoglobinemia
* due to metabolites
54
use of Prilocaine
* largely limited to use in **dentistry**
55
Bupivacaine is an ester or amide? duration of action
* amide
* long duraction of action
56
adverse effects of Bupivacaine
* cardiotoxicity
57
Bupivacaine has a higher sensitivity to motor block or sensory block
* more potent sensory block than motor block
58
use of Bupivacaine
* epidural during labor and childbirth
59
MOA of Ropivacaine
* **amide**
* **long acting**
* the S **enantiomer** of bupivacaine
* less lipid soluble and **cleared more rapidly** than bupivacaine
* less cardiac toxicity
60
use of Ropivacaine
* peripheral and epidural block
* **vasoconstricting** effects at clinical doses
* don't need to add epinephrine
61
Is Mepivacaine an ester or amide
amide
62
Is Etidocaine an ester or amide
amide
63
Does Etidocaine have more blocking effect on motor or sensory
* **inverse differential block**
* ****may cause motor block before or without sensory block
64
Is Articaine an ester or amide
* amide
* also has an additional ester group
65
use of Articaine
dental medicine
66
Is Dibucaine an ester or amide
* amide
* topical use
67
What is the Dibucaine number test
* The dibucaine number is a measure of activity of **butyrylcholinesterase** (dibucaine inhibits wildtype)
* Used to differentiate individuals who have **mutations and deficiencies**.
* number of **80** or below is considered deficient
68
MOA of Diazepam?
acts on **GABAA** receptor to facilitate GABA-mediated presynaptic inhibition in the spinal cord
69
dose of Diazepam in use as muscle relaxant produces what side effect
heavy sedation
70
MOA of Baclofen
* agonist at **GABAB** receptors
* **opens K+** channels -\> hyperpolarizaiton
* **inhibits Ca2+** influx -\> decreases transmitter release
71
MOA of Tizanidine
* **alpha 2 receptor agonist**
* produces both **pre** and **post synaptic** inhibition of spinal cord synaptic activity to decrease muscle spasticity
* **inhibits pain transmission** in dorsal horn
72
side effect of Tizanidine
sedation
73
MOA of Dantrolene
* **inhibits ca2+ release** from sarcoplasmic reticulum
* **interferes with excitation-contraction coupling** of actin and myosin in skeletal muscle fiber
74
Use of dantrolene
* tx
* **neuroleptic malignant syndrome**
* **malignant hyperthermia**
75
MOA of Botulinum toxin
* inhibits ACh release from berve at NMJ
76
use of Botulinum toxin
* used **locally** to control muscle spasms following **stroke** or neurological injury
77
List the drugs for acute local muscle spasms
* Cyclobenzaprine (flexeril)
* Carisoprodol (soma)
* Metaxolone
* Methocarbamol
78
main side effect of drugs for acute local muscle spasms
* significant sedation
