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Local Anesthetics
Exam I stuff
120
Pharmacology
Graduate
01/07/2013

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Term
Local Anesthesia can be accomplished by what substances?
Definition
Amines, alcohols, and toxins
Term
T or F? LA's are capable of producing reversible blockade of conduction of nerve impulses
Definition
True
Term
How do LAs differ?
Definition
structure, speed of onset, doa, potency, protein binding, solubility
Term
cocaine is found in the leaves of what shrub in andes mts in south america?
Definition
Erythroxylon Coca
Term
Einhorn prepared the first synthetic La called?
Definition
procaine
Term
Name the first amide anesthetic?
Definition
Dibucaine
Term
Lidocaine was synthesized by?
Definition
Lofgren
Term
explain MOA of LAs?
Definition
LAs produce a reversible, dose dependent blockade of sodium ion influx into nerve cytoplasm
Term
Functional unit of nerve
Definition
axon
Term
nerve cell membrane
Definition
axolema
Term
intracellular contents
Definition
axoplasm
Term
these surround, support, and insulate axon
Definition
scwann cells
Term
bundle of axons
Definition
fascicle
Term
layer of delicate collagen tissue around axon embedding it in the fascicle
Definition
endoneurium
Term
Over-lapping group of cells binding fascicles
Definition
perineurium
Term
layers of connective tissue around fascicles
Definition
epineurium
Term
This is a liquid substance containing proteins and lipids, forms insulating layer around some nerves. Prevents current from leaking out of nerve
Definition
myelin
Term
small, unmyelinated segments between schwann cells. Intense APs jump from node to node in saltatory conduction
Definition
nodes of ranvier
Term
LAs are ______ in aqueous solution
Definition
weak bases
Term
actual drug(LAs) are poorly soluble in h2o and produced as
Definition
hydrochloride salts that are acidic and more stable
Term
Epi breaks down in what solution?
Definition
Alkaline, this is important when preparing LAs with epi, if no acidic solution, epi would break down
Term
this preservative is added to LAs with epi making the pH 4, to further stabalize it
Definition
sodium bisulfite
Term
preservative that is added to MDV, some are paraben derivatives( potent allergen)
Definition
antimicrobial
Term
these can be cytotoxic and should not be added to LAs to be used in spinals or epidurals or iv regional
Definition
preservatives
Term
morphine in liposomes
Definition
depodur
Term
how do liposomes affect LAs?
Definition
slow release of LA to diffusion and prolonged duration( 48-96 hr)
can be used for chronic pain management
Term
available bupivicaine liposome
Definition
exparel
Term
minimum effective dose is used to?
Definition
mimimize LA toxicity, use of lowest effective concentration, and lowest effective volume
Term
higher concentrations of LAs can?
Definition
increase potential for nerve damage
Term
concentration effect of LAs?
Definition
higher concentrations will speed onset and intensity
Term
differential sensitivity of LAs
Definition
effects on diff nerve functions
Term
Structure of LAs
Definition
Hydrophillic,lipophillic portion, ester or amide link
Term
LAs are present in equilibrium as
Definition
ionized (cationic) salt and unionized base
Term
chemical linkage is associated with?
Definition
Metabolism
Term
lipid solubility is assosciated with?
Definition
potency
Term
dissociation constant is associated with?
Definition
speed of onset
Term
protein binding is associated with?
Definition
DOA
Term
Frequency dependent block is associated with?
Definition
sensorimotor discriminations
Term
vasodilation potential is assosciated with?
Definition
DOA, potency
Term
tissue penetration is assosciated with
Definition
speed of onset
Term
what form is primarily responsible for blocking sodium influx
Definition
ionized form
Term
lipophilic end consists of a?
Definition
aromatic ring
Term
hydorphillic end consists of a ?
Definition
amino group
Term
LAs exist in body as?
Definition
weak bases, packaged in salts for stability and water solubility
Term
Ester structure is
Definition
CO
Term
Amide structure is
Definition
NHC
Term
when u increase molecular weight
Definition
u enhance potency and DOA
Term
the lipophilic end is
Definition
lipid soluble, uncharged
Term
the hydrophillic end is an
Definition
amine, ionized portion
Term
What is more cardiac toxic L bupivicaine or the racemic bupivicaine?
Definition
bupivicaine, these two are enantiomers
Term
This is a pure S isomer and is less cardiotoxic as well
Definition
Ropivicaine
Term
the site of action for LAs are
Definition
protein structures
Term
this may be a factor in some toxicity issues
Definition
high protein binding
Term
if highly protein bound how does this affect the placenta
Definition
less crossing unwanted membranes
Term
Lipid solubility affects
Definition
potency
Term
Protein binding affects
Definition
duration
Term
linkage determines?
Definition
metabolism
Term
whats the most supported theory of how LAs work
Definition
Specific receptor theory
Term
LAs block voltage sodium channel and reduce influx of na ions thereby: 3things
Definition
preventing outflow of K, prevent depol., and block AP
Term
Do LAs change membrane potential or threshold
Definition
no
Term
Blockade is dependant on?
Definition
concentration
Term
Blockade requires
Definition
disruption of several contiguous channels to overcome nerve conduction
Term
LAs block voltage sodium channel and reduce influx of na ions thereby: 3things
Definition
preventing outflow of K, prevent depol., and block AP
Term
Do LAs change membrane potential or threshold
Definition
no
Term
Blockade is dependant on?
Definition
concentration
Term
Blockade requires
Definition
disruption of several contiguous channels to overcome nerve conduction
Term
Na channels can be in one of 3 states
Definition
activated open
inactivated closed
rested closed
Term
LAs gain access to receptors in which state
Definition
activated open
Term
LAs bind to the channel in what state
Definition
inactivated closed
Term
other potential site of action for LAs
Definition
K and CA channel, g protein, may explain cardiac effects
Term
rapid or slow firing nerves are blocked first?
Definition
rapid firing
Term
A nerve is divided into
Definition
alpha beta gamma and delta, its myelinated
Term
A alpha nerve
Definition
somatic motor, proprioception
Term
A beta nerve
Definition
touch, pressure
Term
A gamma
Definition
motor to muscle spinde
Term
A delta
Definition
pain, touch, temp
Term
B nerve
Definition
autonomic preganglionic, myelinated
Term
C nerve
Definition
pain, reflex response, autonomic postganglionic, unmyelinated
Term
where do LAs work in type C fibers
Definition
at breaks in myelin
Term
where do LAs work in type A delta
Definition
at nodes of ranvier
Term
when nodes of ranvier are exposed to LA in high concentration, how many nodes need to be blocked to prevent transmission of the impulse?
Definition
2 or 3
Term
why do we see diff blocks?
Definition
nerve function affects sensitivity
fiber diameter and myelination determine conduction velocity
fibers may have some differences in resistance to block
Term
whats the order of blockade of nerve fibers
Definition
BCA, dgba
Term
What we see, order of block?
Definition
Autonomic
sensory
motor
proprioception (all students must pass)
Term
LAs cause vasodilation except for
Definition
cocaine
Term
differing vasodilation properties can play a role in
Definition
potency
Term
the greater the lipid solubility, the more?
Definition
potent
Term
pKa determines
Definition
how much of drug is ionized, and influences speed of onset
Term
closer to physiologic PH means it is
Definition
faster
Term
Cmin stands for
Definition
minimum blocking concentration
Term
is tachyphylaxis seen when dosing intervals are short enough to prevent pain
Definition
no
Term
do long intervals resulting in pt pain cause tachyphylaxis?
Definition
yes it hastens it
Term
the MOA is unknown, thought to be central spinal acting mechanism, what topic is this regarding?
Definition
tachyphylaxis to LA
Term
absorption and distribution is only a factor with what type of LAs
Definition
topical
Term
Plasma concentration is determined by
Definition
rate of tissue distribution and rate of drug clearance and tissue absorption
Term
absorption and distribution are more critical in determining
Definition
the rate of offset of anesthesia
Term
Absorption is affected by what 3 factors
Definition
site of injection
drug tissue binding
presence or absence of vasoconstrictors
Term
injection into a highly vascular area results in
Definition
rapid absorption
Term
Absorption is modified by what 3 factors
Definition
site of injection
drug tissue binding
presence or absence of vasoconstrictors
Term
injection into a highly vascular area results in
Definition
rapid absorption
Term
Factors that affect absorption include
Definition
tissue blood flow
lipid solubility of agent
pt age and cv status
Term
maximum blood levels for regional occur in what order
Definition
intercostal, caudal, epidural, brachial plexus
Term
these reduce systemic absorption of LA from site
Definition
vasoconstrictors
Term
In spinal anesthesia epi acts directly on the cord, acting on alpha receptors which inhibit release of what
Definition
substance p
Term
epi prolongs effect of LA by what percent
Definition
50%
Term
alpha 2 agonist that can be added to produce analgesia in its own right
Definition
clonidine
Term
Vasoconstrictors are less effective in
Definition
highly lipid soluble long acting drugs b/c they are highly tissue bound
Term
this linkage is widely distributed after IV administration, sequestration in fat, after initial rapid distribution phase( highly perfused organs) and slower distribution phase (muscle and gut)
Definition
amides
Term
this structure has short plasma half lives
Definition
esters
Term
these are hydrolyzed rapidly by plasma cholinesterase, resulting in very short plasma half lives
Definition
Esters
Term
this is hydrolyzed by hepatic microsomal enzymes cp450
Definition
Amides
more LA toxicity in patients with impaired liver func
Term
In normal liver function it can take how long to metabolize lidocaine
Definition
1.8hrs
Term
in liver failure it can take how long to metabolize lidocaine
Definition
6hrs
Term
this can extract some amide LA from circulation limiting amt sent to systemic circulation
Definition
pulmonary extraction
Term
other drugs competing for cp450 can
Definition
prolong half life
Term
elimination is via
Definition
hepatic clearance primarily
Term
what can decrease hepatic clearance
Definition
hypotension, va's
Term
which amide is metabolized fast?
Definition
prilocaine
Term
which amide is metabolized intermediate
Definition
lido and mepivicaine
Term
which amide is metabolized slow
Definition
etidocaine
bupivicaine
ropivicaine
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