local anesthetics Flashcards
when were procaine and lidocaine first synthesized?
1905 (Einhorn) and 1943 (Lofgren)
at a pH of 7.4, how much dibucaine is in the acidic form?
30%
what are the 3 structural components of a local anesthetic?
aromatic group, ester or amide linkage, amine group
the aromatic group renders the local anesthetic _______.
lipophilic
are ester groups or amide groups favored in dentistry?
amide
why are ester groups NOT favored in dentistry?
- esters are hydrolyzed by pseudocholinesterase and have very short 1/2 life in plasma
- more allergenic
how are amide groups metabolized?
P450 enzymes in the liver, therefore longer 1/2 in plasma than esters
the acidic (unionized) amine form allows anesthetic to ___________ while the basic (ionized) form allows for better ___________ once inside the cell.
cross cell membrane, binding to open form of Na+ channel to inhibit nerve impulse
t/f: slow firing nerves are inactivated slower by local anesthetics. the opposite is true regarding rapid firing nerves.
true
B and C fiber fxns are more or less disrupted by local anesthetics than larger diameter A fibers
more
t/f: sensory nerves are homogeneous in size and sensitivity
false. heterogeneous
pain is the ____sensitive sensation while ______ is the least.
most, deep pressure
the faster a fiber is blocked, the _________it takes to recover.
longer
___________produces sensory anesthesia at 1/3 the concentration for motor blockade, but ________ shows no selectivity. which is favored during childbirth epidural?
bupivacaine, etidocaine, bupivacaine
inflamed tissue is _____difficult to anesthetize due to lower pH.
more
anesthetic must be _________ enough to diffuse into site of action and _________ to bind to proteins and increase duration or action.
hydrophilic, lipophilic
the most lipophilic anesthetics
bupivocaine, etidocaine, ropivacaine
middle range lipophilic anesthetics
lidocaine, mepivacaine, prilocaine
least lipophilic anesthetics
chloroprocaine
most local anesthetics are prepared as a water-soluble _______ salt at a pH of _______.
HCl, 6 or 7
if epi is included in local anesthetic, pH is lowered to _______ in order to __________. _________ at ejection site usually neutralizes this. ______ might be added prior to injection to increase circulation of free base.
4 or 5, stabilize epinephrine, buffering capacity, NaHCO3
CNS affects of local anesthetics
- very sensitive to LAs
- too much can affect CNS activity (dizziness, slurred speech, unconsciousness, death)
cardiovascular affects of LAs
- block Na+ and Ca2+ channels
- therefore depress pacemaker activity, excitability, conduction
autonomic nervous sys affects of LAs
- depress contractility
- produce hypotension
- inhibition of sympathetic responses
bupivacaine is especially __________ because it binds tighter to ______ channels and leaves __________.
cardiotoxic, Na+, slower
what is maximum epi per session for uncompromised pt. vs. compromised pt.
200ug, 40ug
lidocaine and procaine are potent ________, therefore epinephrine is administered to provide________.
vasodialators, vasocontriction
local anesthetics bind to plasma _________ (_________ and _______), while unbound drug is free to diffuse to CNS, various tissues and placenta. liver absorption and metabolism important to keep amide LAs low.
proteins (alpha1- glycoprotein, albumin)
esters metabolized very quickly. t1/2 for procaine is ______.
esters with __________ are hydrolyzed very rapidly by ______________.
p-aminobenzoic acid, pseudocholinesterase
amide t1/2 is __________, which is limited by hepatic blood flow
1.5-3.5 hours
first step in amide metabolism is __________.
dealkylation
the 2 exeptions to amide metabolism
- prilocaine- secondary amine, no dealkylation required, extrahepatic metabolism
- articaine- inactivated in the blood by esterase
the most serious adverse affects of LAs result from___________ by
operator error, excessive dosage, intravascular injection (just 10mg of lidocaine injected into a vertebral a. can induce convulsions)
excessive admin or intravascular injection may result in _______, _______ or ________.
convulsions, respiratory arrest, cardio collapse
convulsion tx (the rest are common sense tx)
benzodiazepine, thiopental, succinylcholine (symptoms only)
pregnancy anesthetics
lidocaine, prilocaine category B, articaine, mepivacaine, bupivacaine catercory C
