Week 2 Flashcards
New FDA law requires LA carpule labeling to say?
1.7 mL
Name 2 buffering agents that can be in the carpule
sodium hydroxide and sodium chloride
The vasoconstrictor present in the carpule
epi or levonordefrin
This vasoconstrictor preservative helps decrease the solution pH to delay the onset of the LA
sodium bisulfite
If a pt reported that they had an allergic rxn to a LA before 1984, then what were they probably allergic to?
parabens
Esters are metabolized in the ______ while amides are metabolized in the _________
blood; liver
T/F: Allergic rxns are rare with esters.
False bruh they’re hella common
ALL injectables LAs are?
amides
Describe the chemical structure of LAs
1) lipophilic aromatic ring
2) intermediate linkage
3) hydrophilic terminal amine
Which part of the chemical structure of LAs determines if it’s an ester/amide?
the intermediate linkage
Once the LA has gained a ________ ion, it’s now in it’s ___________ form
H+; active
L.A. molecules in the cartridge include anions and cations. How do they differ with their onset?
more anions: low pKa, more base, fast diffusion, rapid onset
more cations: high pka, less base, slow diffusion, slow onset
Infected tissues are acidic. What happens if you inject LA into this acidic tissue?
since the LA is also acidic, then there will be less molecules that cross the membrane = INADEQUATE ANESTHESIA
L.A. must penetrate _______mm of myelinated nerve length (3-4 nodes of Ranvier) to block a nerve impulse
↑ — of L.A. is required for large nerves (inferior alveolar n.)
8-10mm
↑___________ of L.A. is required for large nerves (inferior alveolar n.)
volume
Describe the onset if there is a high concentration of the LA and it has a low pKa
rapid onset
What happens to the dosage if the lipid solubility decreases?
have to increase the dose to enhance diffusion of drug through the nerve
What happens to the duration of the LA if there is increased protein binding?
increased duration
T/F: LAs are vasodilators
true
Pharmacokinetics of LAs include…. (fat list)
1) onset of action
2) induction
3) recovery from block
4) reinjection
5) duration / potency
6) distribution
7) absorption
8) biotransformation (metabolism)
9) excretion
10) systemic effects
period from LA deposit to blocked impulse conduction
onset of action
the primary factor of onset of action of a LA
pKa!!!
low pKa = rapid onset
secondary factor of onset of action of LA
site!
small diameter nerves have rapid onset
primary factor of induction of LAs
initial concentration
increased conc = rapid onset
Name some areas in the body where the anesthetic loses concentration from
-tissue fluid
-capillaries
-lymphatics
-anatomic barriers
Degree of ____________ to receptor site is primary factor for recovery from LA block
binding
T/F: Recovery is a slower process than induction
True
What will occur if i try to reinject a pt and their nerve fibers have fully recovered?
tachyphylaxis -> the LA is ineffective
3 factors that affect potency of LA
1) protein binding
2) vascularity of injection site
3) vasoconstrictor in LA
Examples of highly vascular organs
brain
heart
liver
lungs
kidneys
Which route of administration will allow for increased absorption?
topical
T/F: The presence of a vasoconstrictor increases absorption.
false!! it decreases it cuz if you’re constricting the blood vessel aka making the diameter smaller then less flows into bloodstream
Biotransformation refers to the ____________ of a drug
metabolism
Name 3 ester LAs
- procaine
- tetracaine
- benzocaine
Name 5 amide LAs
- lidocaine
- mepivacaine
- bupivacaine
- prilocaine
- articaine
which amide LA has shortest half life?
Articaine
Why is there an increased risk of systemic toxicity of LAs in severe renal disease?
due to build up of drug when not cleared by kidneys
Although small amounts of both esters and amides L.A.s are excreted unchanged in urine, which is excreted in a greater percent this way?
amides
At what point can LAs affect the CNS and CV system
after they are absorbed into blood (before metabolized)(↑blood levels = ↑toxicity)
Toxicity and adverse reactions of LAs are directly related to what? (9)
1) Nature of specific L.A. (vasodilation)
2) Concentration of drug
3) Route of administration
4) Dose administered
5) Rate of injection
6) Vascularity of site
7) Age of patient
8) Weight of patient
9) Health of patient
What color is the band for lidocaine -> 2% 1:100,000 epi
red
Order of selection of LAs
1) duration of pain control needed
2) need for post op pain control
3) patient’s health assesment and current meds
4) allergic to the LA or sodium bisulfite
5) need for hemostasis
If a pt is allergic to wine, dried fruit, or dried potatoes, they we assume they have a ___________ allergy
bisulfite
highest dose of epi
1: 50,000
T/F: Most LAs are short-acting.
False! They’re intermediate-acting so they last for about a hour
Characteristics of lidocaine
-good for hemostasis if 1:50,000 epi
-duration: 60 mins
-good as topical
2-3 min onset
MRD = 500mg
Characteristics of mepivacaine
-not used for hemostasis
-w/levo it lasts 60 mins
-NOT an effective topical agent
-onset is about 2 mins
-MRD = 400 mg
Characteristics of prilocaine
-least toxic LA in dentistry
-good for pregnant pts
-risk of methemoglobinemia
-w/ epi it last 60-90 mins
-onset is 2 mins
MRD = 600 mg
Characteristics of articaine
-very lipid soluble
-good choice in CV and liver disease pts
-have to give with vasoconstrictor
-duration = 45-75 mins
-NOT an effective topical
-onset: 3 mins
MRD: none
Which LA is metabolized primarily in the blood? where is the rest of it metabolized?
articaine
10% in liver
Characteristics of bupivacaine
-most potent and most toxic!!!
-good for long treatment
-NOT available w/o epi
-duration: 1.5-3hrs
-NOT an effective topical
-onset: 5-10 mins
-MRD: 90 mg
The CNS is very sensitive to high levels of LA because they?
readily cross the blood-brain barrier
Has this pt suffered from a moderate or high overdose of LAs?
presents with:
increased HR, RR, BP, and also has muscle twitching with tremors
moderate
Has this pt suffered from a moderate or high overdose of LAs?
presents with:
decreased HR, RR, BP, they’re convulsing and experiencing unconsciousness
High!! They progressing to respiratory arrest cuz of CNS depression
Has this pt suffered from a moderate or high overdose of LAs?
presents with:
increased HR, RR, BP, headache and feeling lethargic
moderate! they have initial cardiovascular stimulation
Has this pt suffered from a moderate or high overdose of LAs?
presents with:
decreased HR, RR, BP, slurred speech, disoriented
high! progressing to cardiac arrest and cardiac depression
4 functions of vasoconstrictors
1) constrict blood vessels @ site
2) increase duration of LA
3) provides hemostasis at injection site
4) decrease absorption rate of LA
Which vasoconstrictor affects alpha and beta receptors equally?
epi
T/F: Levonordefrin affects the alpha receptors more.
True! 75% is alpha and 25% is beta
An overdose usually occurs via which route?
intravascular injection
symptoms of an overdose
1) dysrhytmias
2) dramatic increase in HR
3) increased BP
4) headache
5) hyperventilation
6) tremors
7) anxiety
Absolute contraindication for LA
allergy
Relative contraindications of LA
1) H2 receptor blocker
2) beta blocker
3) CNS depressants
Absolute contraindications for vasocontrictors
basically anything heart related
hypertension
angina
arrythmias
hyperthyroidism
glaucoma
Relative contraindications of vasoconstrictors
CVD pts
Tricyclic antidepressants
nonselective beta blocker
digitalis
MRD is based on:
-maximum dose per appointment
-body weight
How do we calculate the amount of LA in 1 carpule
take the % x 10
take that number x 1.8ml/carpule
MRD and AMD of lidocaine
MRD: 3.2 mg/lb
AMD: 500 mg
What is the MRD of a 120lb pt if you wanna give them lidocaine?
MRD of lidocaine is 3.2 so take that x pt’s weight
3.2 x 120 = 384mg of lidocaine is the max dose
Calculate the maximum amount of carpules if the pt weighs 120lbs and the max dose is 384 mg of lidocaine.
20 x 1.8 = 36mg of lidocaine
384/36 = 10.6 carpules
How much lidocaine did you administer if you gave a pt 5 carpules?
in one carpule there is 36 mg of 5 x36 = 180 mg of lidocaine
MRD and AMD of prilocaine
MRD: 4 mg/lb
AMD: 600mg
MRD of vasoconstrictor in a healthy patient
EPI: 0.2 mg
Levonordefrin: 1 mg
MRD of vasoconstrictor in a cardiac or medically compromised patient
EPI: .04mg
Levonordefrin: 0.2 mg
Calculate the amount of epi in one carpule
1:100,000 epi -> .01mg
.01mg x 1.8 = .018 mg epi/carpule
Calculate the max amount of epi carpules in a healthy pt and cardiac pt
Healthy: 0.2/.018 = 11 carpules max
Cardiac: .04/.018 = 2 carpules max
