Unit 4: Local Anesthetics Flashcards
what was the first local anesthetic?
cocaine
cerebral stimulating qualities
ophthalmology (1884)
localized vasoconstriction: shrink nasal mucosa
1st synthetic ester was ___
procaine
1st synthetic amine was ____
lidocaine
Name the class of antidysrythmIc drugs that are also LA
Antiarrhythmic Drug Classes:
Class I - Sodium-channel blockers.
what is the introp dose of lidocaine?
1mg/kg over an hour
what is the initial dose of lidocaine for induction?
1-2mg/kg over 2-4 minutes
what is the drip dose for lidocaine?
1-2mg/kg/hr
stopped 12-72 hours after
discuss the plasma lidocaine concentrations with the side effects
local anesthetics (LAs) have a (1) _____ portion connected by a (2) _____ chain to the (3) ______ portion.
lipophilic
hydrocarbon
hydrophilic
what are the two classess of local anesthetics?
amine and ester
the standard LA is ____
lidocaine
LA blocks pain and ____
motor
when you give lidocaine the patient will often say it taste like ____
metal
we give lidocaine to blunt the airway reflexes. What are those?
swallowing, gagging, coughing
Lidocaine have vaso_____ properties
vasodilatory
you give your pt lidocaine and they are having tinnitus and skeletal muscle twitching. What plasma lido concentration would you suspect?
5-10mcg/ml
Bond between () & () classifies it as ester or amide
1 and 2
the hydocarbon/intermediate chain classifies it as ester or amide
esters have 1 i
amines have 2 i’s
LA are weak ____ with a pH of 6
bases
sodium bisulfite makes the LA more ____ with epi
soluble
non ionize % is the largest indicator of ___ solublility
lipid
the higher the nonionized% of the drug the more ____ the drug
lipid soluble it is
and sometimes potent
bupivicaine is more potent what lidocaine even with a lower nonionized component? why?
lidocaine causes vasodilation and this causes it to travel away from the site of action
bupivicaine is also more lipid soluble
liposomes do what? what are the drugs that do this(3)?
do they cause an increase or decrease in toxicity?
can be compared to an extended release
what is the MOA of LA?
Binds to inactivated closed @ inner voltage-gated Na+ channels
Block/inhibit Na+ passage in nerve membranes
LAs Block/inhibit Na+ passage in nerve membranes, What 3 things does this cause?
Slowed rate of depolarization
Does not reach threshold
No action potential
what factors affect the LA blockade? (3)
Lipid solubility or non-ionized/unionized form
Repetitively stimulated nerve (more sensitive, reacts well with LA)
Diameter of the nerve (bigger the nerve the more drug we need)
what are other targets of the LA besides the fast NA channels?
K channels
Ca ion channels
GPCR
A
minimum effective concentration (MEC) is ___
At least 2, preferably 3 Nodes of Ranvier (1 cm) blocked to gain numbness
comparable to MAC with volatiles
preganglionic B fibers are the ____
fastest
Myelinated A (medium) and B fibers (faster) > Unmyelinated C fibers (small)
what pt population have increase sensitivity to LA?
preg women because they have a decrease in plasma cholinesterase
- you will give a lower dose, especially with the esters
- can travel into the fetus, who has more acidic blood, and turns into ionized form and cause ion trapping
- the fetus can become bradycardic and comatose
usually all LA are ___% lipid soluble
50
pKa’s closest to physiologic pH = most ______ OOA
rapid
what 4 factors influence absorption?
Site of injection
Dosage
Use of Epinephrine
Pharmacologic characteristics of the drug
Rate of tissue distribution
***Lipid solubility is the _____ determinant of potency
primary
rate of clearance is dependent on what 2 things
CO and protein binding
% bound of a drug is _____ related to % plasma
inversely
the highest protein binding drug has the ____ metabolism
slowest
describe metabolism of amides
Amides: Microsomal enzymes in the liver
Most rapid: Prilocaine
Intermediate: Lidocaine & Mepivacaine
Slowest: Etidocaine, Bupivacaine & Ropivacaine
describe the metabolism of esters
Esters: Hydrolysis by cholinesterase enzyme in plasma > liver
except with Cocaine: Liver)
Metabolite: para-aminobenzoic acid (PABA): allergies
Amides are slower than esters
cocaine is an ester but is mainly metabolize in the ___
liver
what is the usual reason pt have allergies to LA
PABA
para-aminobenzoic acid
this is the metabolite for ester LA, so if they have this allergy you will use an amide
what are the three main LA that have first pass puml extraction
these are inactive once in the lungs
Lidocaine, bupivacaine (dose dependent), and prilocaine
main elimination and clearance of LA is in the ___
kidney
Poor water solubility
Unchanged drug in urine = 5%
Cocaine is 10 to 12%
PABA through urine
true
A and D
clearance from primary site of action
the higher the protein binding and ____ it is available to be metabolized
lesser
