Module 5 Flashcards
local anesthetics are manufactured in ____ use cartridges
single
how many mL does each carpule contain
1.8 mL
2 % solution is how many mg per carpule
36
3 % solution is how many mg per carpule
54
4 % solution is how many mg per carpule
72
0.5 % solution is how many mg per carpule
9 mg
what are the different percentages of solution that local anesthetics are produced as
0.5, 2, 3, & 4
what are the carpule contents of local anesthetic agents
- local anesthetic drug
- sodium hydroxide
- sodium chloride
- vasoconstrictor
- vasoconstrictor preservative
what is often used as the vasoconstrictor in local anesthetic agents
EPI or levonordefrin
what is often used as the vasoconstrictor preservative
sodium bisulfite
what effect does the sodium bisulfite have
decreases solution pH making it more acidic and DELAYING ONSET
what is a negative aspect of sodium bisulfite in local anesthetic agents
increases likelihood of allergic reactions to occur
prior to 1984 local anesthetic solutions without EPI added ___ as a preservative
methylparaben
what are the 2 groups of local anesthetics
- esters
- amides
which group of local anesthetics has an increased risk of allergic reactions
esters
which group of local anesthetics is metabolized in the blood via pseudocholinesterase
esters
which group of local anesthetics is metabolized in the liver
amides
which group of local anesthetics is the only one used in dentistry in the US
amides
amides have low __ with esters
cross-hypersensitivity
T/F if you are allergic to one ester then you are most likely allergic to all esters
true
what are the three components of the chemical structure of local anesthetics
- lipophilic aromatic ring
- intermediate linkage
- hydrophilic terminal amine
what determines the potency of the local anesthetic and can penetrate the membrane but not bind to the receptors unless it picks up a H+ ion
lipophilic aromatic ring
what determines if the local anesthetic is an ester or an amide
the intermediate linkage
what dissociates becoming a tertiary amine and enters the nerve to gain a H+ ion and the binds to the receptor site activating the drug
hydrophillic terminal amine
what is the term used to describe the physiological effects of the drug on the body
pharmacodynamics
local anesthetic molecules in the cartiridge include
- cations = RNH+ = active form that CANNOT cross membrane
- anions = RN = inactive lipid soluble form CAN cross membrane
all local anesthetics are ___ solutions before injection
acidic - more cations than anions
T/F all local anesthetics are vasoconstrictors
false - vasodilators
a LOW pKa of a local anesthetic causes what to occur
RAPID onset - fast diffusion across the membrane
a HIGH pKa of a local anesthetic causes what to occur
SLOW onset - slow diffusion across the membrane
what predicts the proportion of acid : base molecules
pKa
A local anesthetic with a low pKa will result in:
a - higher concentration of base molecules, resulting in a fast diffusion across the membrane, resulting in rapid onset
b - higher concentration of acid molecules, resulting in a fast diffusion across the membrane, resulting in rapid onset
c - higher concentration of base molecules, resulting in a slow diffusion across the membrane, resulting in slower onset
a - higher concentration of base molecules, resulting in a fast diffusion across the membrane, resulting in rapid onset
infected tissues are acidic or basic?
acidic (pH of 5-6)
when local anesthetic (acidic) is injected into an infected tissue (acidic) what occurs
INADEQUATE ANESTHESIA - low concentrations of molecules can cross the membrane
RNH+ molecules cannot dissociate H+ ions in acidic tissues so what occurs
active form CANNOT enter the cell membrane so INADEQUATE ANESTHESIA
local anesthetics must penetrate ___ mm of myelinated nerve length to block a nerve impulse
8-10 mm (3-4 nodes of Ranvier)
what is required for large nerves
increased volume of local anesthetics
what is the impact of high concentrations
increased diffusion across the membrane leading to RAPID ONSET
what is the impact of a low pKa
increased RN molecules and base leading to RAPID ONSET
what is the impact of high lipid solubility
increased POTENCY and decreased dose needed because it enhances the diffusion of the drug through the nerve
what is the impact of high protein binding capacity
increased DURATION - binds more strongly to the receptor, prolonging the anesthetic presence at the site of action
what is the impact of increased vasodilation
decreased POTENCY + decreased DURATION + increased DOSE needed
because vasodilation increases blood flow and increases the rate of removal of local anesthetics from the site of action
what is the term used to describe the action of the drug within the body
pharmacokinetics
what is included in pharmacokinetics
- onset of action
- induction
- recovery from block
- reinjection
- duration / potency
- distribution
- absorption
- biotransformation
- excretion
- systemic effects
what is a secondary factor of the onset of action
site - a small diameter nerve = rapid onset
what is the period from local anesthetic deposit to blocked impulse conduction
onset of action
what is the diffusion of molecules across a membrane
induction of local anesthetics
what is the primary factor of induction of local anesthetics
initial concentration
what do anesthetics lose concentration from
- tissue fluid
- capillaries
- lymphatics
- anatomic barriers
what is the reversal of local anesthetic action
recovery from local anesthetic block
what is the primary factor of recovery from local anesthetic block
degree of binding (slower process than induction)
if nerve fibers are only partially recovered a ___ volume is effective with rapid onset
small
if nerve fibers are fully recovered what occurs
tachyphylaxis / tolerance / ineffective block
the degree of protein binding at the receptor site controls which of the following:
a - the duration of anesthetic action
b - the speed of the nerve recovery from local anesthesia
c - both are correct
c - both are correct
what is the duration of local anesthetic related to
potency
what are the three factors of duration/potency of local anesthetic
- protein binding
- vascularity of injection site
- vasoconstrictor
how does protein binding impact duration and potency
the stronger the binding the longer the duration and the higher the potency
how does vascularity of the injection site impact duration and potency
the higher the vascularity the shorter the duration and the lower the potency
how does the vasoconstrictor of the local anesthetic impact duration and potency
vasoconstriction decreases the blood flow increasing the duration and potency of the local anesthetic
how are local anesthetics distributed
highly vascular organs have higher concentrations
brain, heart, lungs, liver, kidneys
what is directly related to the amount of local anesthetic accumulated in the tissues
toxicity
high rates of absorption lead to to high__
risk of systemic toxicity
what are the 5 components of local anesthetic absorption
- total dose administered
- local anesthetic concentration
- route of administration
- vascularity of administration site
- presence of vasoconstrictor
how does increased dose impact absorption
increases absorption
all molecules diffuse out of Na+ channels into bloodstream
how does increased local anesthetic concentration impact absorption
increases absorption
how does a topical route of administration impact absorption
increases absorption
how does intravascular injection impact absorption
increases absorption
how does increased presence of vasoconstrictor impact absorption
decreases absorption
ALL local anesthetics are __
vasodilators
an increased half life increases __
risk of systemic toxicity
because drug lingers in tissues for longer
what are examples of ester local anesthetics
- benzocaine
- tetracaine
- procaine
TOPICAL ONLY
what are examples of amide local anesthetics
- lidocaine
- mepivacaine
- bupivacaine
- prilocaine
- articaine
INJECTABLES & TOPICALS
which amide local anesthetics are metabolized only in the liver
- lidocaine
- mepivacaine
- bupivacaine
where is prilocaine metabolized
liver & lungs –> shorter half life
where is articaine metabolized
plasma & liver –> shortest half life
what is the primary excretory organ for all local anesthetics
kidneys
higher blood levels leads to __
increased toxicity
toxicity and adverse reactions are directly related to:
- nature of specific local anesthetic
- concentration
- route of administration
- dose administered
- rate of injection
- vascularity of site
- age of patient (child/elder = low rate of metabolism)
- weight of patient
- height of patient