Exam 2; Local Anesthetics and Spasmolytics Flashcards
This is any agent that can reversibly block the electrical activity of excitable tissues
local anesthetic
What are the two actions of local anesthetics
decrease neuronal conduction
block impulse conduction in the heart
How are local anesthetics used as painkillers
temporary analgesia without loss of consciousness
All local anesthetics have what two ends
automatic (lipophilic)
amino (hydrophilic)
This part of the local anesthetic can get though the neuronal membrane
lipophilic
This part of the local anesthetic is inside the membrane or cell, this end gets ionized
amino
Local anesthetics in the non-ionized form get through the neuronal membrane and once inside, what occurs
the hydrophilic side is ionized and binds to a specific site on the sodium channel of the excitable membrane/tissue; blocking the Na channel
What are the three events of local anesthetics blocking the Na channels
decreases neuronal conduction
decreases repolarization rate
increases refractory period
What will increase effect of the local anesthetic
Na channels are open; neurons not fire more rapidly
will have open channels more often and affected more
Which size of neurons are generally more susceptible to local anesthetics
smaller neurons
pain more susceptible than motor neurons
Which type of myelination of neurons is more susceptible to local anesthetics
myelinated neurons
Which speed of firing is more susceptible to local anesthetics
faster the firing rate the more susceptible
What is the sensitivity ranking regarding, warm, cold, pain, motor, and touch/pressure
pain > cold > warm > touch/pressure > motor
What is the major distinction between local anesthetics
their duration of action
This type in linkage has a relatively short duration
ester linkage
The ester is metabolized by what
plasma cholinesterase
What is the half like of ester linked LAs
minutes
This type of linkage is fairly long
amide linkage
The amide is metabolized by what
in the liver by CYP450
What is the half life of amide linked LAs
hours
Local anesthetics are weak bases or acids
bases
In an acidic environment, the local anesthetic will be what
more ionized
In infected tissues which tend to be more acidic, what happens to the local anesthetic
the molecules don’t readily enter the cell and LA activity is decreased
Repeated use of an epidural anesthetic can do what
lower pH and cause tachyphalaxis
These are used with local anesthetics to increase duration of action (except for cocaine)
vasoconstrictors (like Epi.)
What are the three topical routes of administration of a LA
skin
mucosa
eye
What are the three routes of administration of injection of LA
infiltration
direct nerve block
spinal or epidural
Regardless of route of administration, all local anesthetics can be what
systemically absorbed
Which linkage of LA is more likely to cause an allergic reaction
esters
This ester LA inhibits the re-uptake of NE in the CNS
cocaine
What is cocaine used for
ophthalmic; nasal surgery
This is an ester LA with low solubility so a long duration of action and is used topically
benzoxaine
This ester LA has a short half-life and is not used topically because it doesn’t readily pass through the mucous membranes
procaine
These are ester LAs that are used in the eye
benoxinate and proparacaine
These is an amino amide LA used IV for cardiac arrthymia and produces a lupus like syndrome in slow acetylators
procainamide
This is the most common amino amide LA and is used IV for arrthymias
lidocaine
What are some CNS side effects of lidocaine
tremors
slurred speech
drowsiness
What is it that distinguishes the amino amide LAs
all the names contain “two i’s” and “-caine”
articaine
mevpicane
What are the six CNS side effects of local anesthetics
disorientation drowsiness slurred speech tongue numbness tinnitus (ringing in the ears) burred vision
What is the side effect on the cardiovascular system of LAs
alter the heart rhythm
What are the two specific side effects of cocaine
vasoconstrictor
CNS effects
This is an irreversible sodium channel blocker that can cause muscle weakness, respiratory paralysis, and death
tetrodotoxi
This is an irreversible sodium channel blocker that can cause muscle weakness, respiratory paralysis, and death; from the red tide
saxitoxin
This is excessive muscle contraction; muscle hypertonia
spasticity
What results in spasticity
neuronal damage; injury, stroke, MS, CP, ALS
What is the treatment for spasticity
either alter the innervating neurons or act directly on muscle
This is a GABA agonist that increases the activity of inhibitory neurons; treatment for spasticity
baclofen
This is a minor tranquilizer and muscle relaxant that increases GABA activity; treatment for spasticity
diazepam and other benzodiazepines
This is an α2 agonist; inhibiting motor neurons; treatment for spasticity
tizanidine
This is a treatment for spasticity; neuronal effects
botulinum toxin
This acts directly on muscle cells and inhibits the stimulus induced release of Ca from the muscle SR; decreasing availability of Ca for muscle; treatment for spasticity
dantrolene
What are two side effects of dantrolene
muscle weakness
hepatitis
