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Pharmacology Units 1-10 > Unit 3 > Flashcards

Unit 3 Flashcards

1
Q

Which type of sensory nerves freeze best?

A

unmylenated

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2
Q

What are desirable properties of LA

A
  • non irritating
  • does not cause permanent alteration of nerve structure
  • systemic toxicity should be low
  • effective regardless of whether it is injected or applies locally
  • short time of onset
  • duration of action long enough to allow for comort during procedure but short enough to limit recovery time
  • sufficient potency to provide complete anesthesia without the use of harmful concentrated solutions
  • free of potential allergens
  • stable in solution and readily undergo biotransformation in the body
  • sterile (capable of being sterilized)
  • cost effective
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3
Q

What are some factors a hygienist must weigh when selecting LA?

A
  • duration of action of LA agent
  • length of time pain control needed
  • duration of pulpal and soft tissue anesthesia
  • need for post treatment pain control
  • health status of the client
  • client’s medications
  • allergies to LA agents
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4
Q

How does concentration affect LA action?

A

higher = more cations diffuse + rapid onset

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5
Q

how does pKa affect LA action?

A

lower pKa = faster onset

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6
Q

How does lipid solubility affect LA action?

A

increased solubility = increased potency

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7
Q

How does protein binding affect LA action?

A

increased ability of cations to bind to receptor sites = duration

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8
Q

How does non-nervous diffusion affect LA action?

A

the more a solution diffuses away from the nerve the longer the onset

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9
Q

How does vasodilation affect LA action?

A

if the solution increase vasodilation, blood flow will carry solution away faster therefore decreasing the potency and decreasing the duration

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10
Q

How does the perineurium thickness affect LA action?

A

increased thickness decreases the rate of onset

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11
Q

How are LA agents divided chemically?

A
  • esters and amides
  • all injectable LA agents are amides due to increased risk of allergic reaction to esters
  • LA molecules consist of 3 components: lipophilic aromatic ring (facilitates penetration and increases potency), an intermediate chain (ester or amide which predetermines biotransformation), hydrophilic terminal amide
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12
Q

How are LA agents divided chemically?

A
  • esters and amides
  • all injectable LA agents are amides due to increased risk of allergic reaction to esters
  • LA molecules consist of 3 components: lipophilic aromatic ring (facilitates penetration and increases potency), an intermediate chain (ester or amide which predetermines biotransformation), hydrophilic terminal amide (wich can exist as a cation or anion)
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13
Q

What is a dissociation constant?

A
  • pKa of a molecule represents the pH at which 50% of the molecules exist in the lipid soluble tertiary form and 50% are in the quaternary water soluble form
  • higher pKa=fewer base molecules therefore has a slower onset
  • lower pKa=more base molecules=rapid onset
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14
Q

What happens in an area of infection?

A
  • normal pH of tissue is 7.4
  • decreased pH favours water soluble cation which decreases penetration
  • how might this impact selection of an LA agent?
  • other factors can include increased edema which will diffuse/dilute the LA solution
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15
Q

What are the properties of free base (anion)?

A
  • viscid liquids or amorphous solids
  • fat soluble (lipophilic)
  • unstable
  • alkaline
  • uncharged, nonionized
  • penetrates nerve tissue
  • form present in tissue (pH7.4)
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16
Q

What are the properties of salt (cation)?

A

-crystalline solids
-water soluble (hydrophilic)
-stable
-acidic
-charged, cation(ionized)
-active form at site of action
form present in dental cartridge (pH 4.5-6.0)

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17
Q

Why is a local anesthetic solution with a pKa closer to the tissue pH of 7.4 able to penetrate the nerve more effectively leading to greater potency?

A
  • there are close to equal amount of lipid and water soluble molecutes
  • increased presence of H+: equilibrium shifts to left RNH+>RN+H; anesthetic solution has higher concentration of ionized cationic form (water woluble), active form of molecule
  • decreased presence of H+: equilibrium shifts to right RNH+
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18
Q

Why might it be difficult to re-anesthetize an area if freezing came out prior to a procedure being completed?

A
  • at reinjection, the core fibers contain less than the mantle fibers but are partially anesthetized, therefore less solution is needed to reach threshold making it more rapid to regain adequate pain control with less volume
  • clinician may encounter greater difficulty reestablishing pain control
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19
Q

What is tachyphylaxis?

A

occurs with re-anesthetizing tissue

-it is an increased tolerance to a drug

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20
Q

Why might it be difficult to re-anesthetize an area if freezing came out prior to a procedure being completed?

A
  • at reinjection, the core fibers contain less than the mantle fibers but are partially anesthetized, therefore less solution is needed to reach threshold making it more rapid to regain adequate pain control with less volume
  • clinician may encounter greater difficulty reestablishing pain control
  • tachyphylaxis may occur
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21
Q

What is tachyphylaxis?

A

occurs with re-anesthetizing tissue

-it is an increased tolerance to a drug

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22
Q

What is the main factor that influences the onset of action of a local anesthetic agent?

A

-determined by the pKa, the administration site (smaller nerve trunks and those with thinner perineurium), as well as the accuracy of the operator

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23
Q

What is the main factor that influences the onset of action of a local anesthetic agent?

A
  • determined by the pKa, the administration site (smaller nerve trunks and those with thinner perineurium), as well as the accuracy of the operator
  • diffusion - movement of LA solution toward the nerve fibers (consider mantle fibers compared to core bundles)
  • induction time - time from initial deposition to complete conduction blockage
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24
Q

What is onset of action of an anesthetic?

A

defined as the time from deposition to profound anesthesia

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25
Q

What are factors that affect LA action?

A
  • concentration: higher=more cations diffuse causing rapid onset
  • pKa: lower pKa=faster onset
  • lipid solubility: increased solubility=increase potency
  • protein binding: increased ability of cations to bind to receptor sites=duration
  • non-nervous diffusion: the more a solution diffuses away from the nerve
26
Q

What are the 3 components that LA molecules consist of?

A
  • lipophilic aromatic ring
  • an intermediate chain (ester or amide)
  • hydrophilic terminal amide
27
Q

What are the two chemical groups that LA agents are made up of?

A

esters and amides

28
Q

Why are injectiable LA agents amides?

A

due to increased risk of allergic reaction to esters

29
Q

What is the role of the aromatic ring (lipophilic)

A

facilitates penetration and increases potency

30
Q

What is the role of the intermediate chain (ester or amide)

A

predetermines biotransformation

31
Q

What is the role of the terminal amine (hydrophilic)

A

can exist as a cation or anion

32
Q

What is the pharmacodynamics of LA

A

defined as physiolical effects of the drugs on the body and the mechanism of action and relationship between drug concentration and effect

33
Q

Why are acids (HCL) added to LA

A

to become more water soluble and stable

34
Q

What is the pH of LA without vasoconstrictors

A

5-6

35
Q

What is the pH of LA with vasoconstrictor

A

3.3-5.5

36
Q

Describe the recovery process from an LA block

A
  • slower than induction
  • follows same diffusion patter in the reverse order
  • concentration outside the nerve is depleted by diffusion, dispersion and uptake of the drugs
  • concentration inside the nerve then exceeds the concentration outside reversing the gradient
  • mantle fibers lose before core fibers
  • recovery is slower in areas of decreased vascularity
37
Q

What influences the duration of anesthesia?

A
  • ability of the solution to bind to the receptor sites
  • protein binding - increased protein binding allows the cations (RNH+) to bind firmly so duration is increased
  • vascularity - increased vascularity allows drug to be removed from the area which decreases duration and potency
  • presence of vasoconstrictor - decrease in vasoldilation effect of local anesthetic
38
Q

Describe the distribution of LA

A
  • after absorption into the blood stream, highly vascular organs such as the brain, heart, liver, kidneys and lungs will have a higher concentration of anesthetic
  • toxicity is related to concentration in tissue - and rate of absorption and elimination impact toxicity
39
Q

What is the half life of a drug?

A

period of time that it takes for 1/2 of the drug to be removed from the body

40
Q

Where are most amide anesthetics metabolized?

A

in the liver with the exeption of articain (by plasma pseudocholinesterase like esters)
-excreted primarily by the kidneys

41
Q

Where are most ester anesthetics metabolized?

A

-hydrolyzed by plasma pseudocholinesterase and in the liver (mainly topicals now)

42
Q

Which effects should a dental hygienist be most concerned about?

A
  • nature of drug: all LA solutions are vasodilators and the extent will impact toxicity potential
  • concentration of drug
  • route of administration
  • rate of administration
  • vascularity of area injected
  • age of the patient
  • weight of the patient
  • patient health (impact of ability to excrete or biotransform)
43
Q

What are the two phases of LA effects on the CNS?

A 
Phase I (excitatory phase) - muscle twitching, tremors (low to moderate overdose = elevated blood pressure and elevated heart rate)
Phase II (depressive phase) - CNS depression, unconsiousness, convulsions, hypotension, respiratory arrest (in a moderate overdose, the patient may experience reduced heart rate, blood pressure, and respiration rate, which could lead to circulatory collapse and cardiac arrest)
44
Q

What is the most sensistive system to high blood levels of LA?

A

CNS

45
Q

Describe how concentrations of LA are ‘inversely proportional’ on CNS

A
  • overdose manifests as CNS depression
  • low blood levels may have anticonvulsant properties
  • higher doeses may present in 2 phases (excitatory and depressive)
46
Q

What determines the severity of the overdose reaction?

A
  • TIME LAPSE BETWEEN THE ADMINISTRATION OF LOCAL ANESTHETIC TO REACTION
  • rapidly occurring symptoms are more likely to evolve into a more serious reaction
  • delayed symptoms (after 5 minutes) are usually easily resolved and the reaction is not as serious
  • rare instances, cardiac arrhythmia or hypotension and cardiovascular collapse occur
47
Q

What is the composition of the local anesthetic solution?

A
  1. drug (ester or amide)
  2. vasoconstrictor (epinephrine, levonordefrin)
  3. sodium sulphite (decrease oxidation of epi shelf life 18 months)
  4. sodium hydroxide buffers pH to between 5=6-7
    5 sodium chloride buffer which creates injectable isotonic solution
  5. distilled water
  6. methyl paraban (bacteriostatic agent in 1984 no longer added due to allergic reasponse)
48
Q

What is MRD?

A
  • maximum recommended dose
  • highest amount of an anesthetic drug that can be safely administered without complication
  • each drug has a MRD for healthy and compromised clients
  • if a vasoconstrictor is added, the MRD is based on which of the 2 drugs reaches MRD first
49
Q

What does ‘limiting drug’ refer to ?

A

whether the vasoconstrictor of the concentration of a drug reaches MRD first in a compromised or healthy client.

50
Q

What is absolute MRD

A

the absolute maximum dose the patient can receive regardless of weight

51
Q

What is MRD based on?

A
  • patients weight
  • drug concentration
  • amount of solution in cartridge
  • maximum recommended dose as provided by manufacturer
52
Q

What is the pharmacology of Lidocaine

A
  • concentration = 2%
  • amount of anesthetic = 20mg/ml
  • MRD = 4.4 mg/kg
  • maximum recommended does per appointment = 300mg
  • blue label = plain
  • green label = 1:50,000 epinephrine
  • red label = 1:100,000 epinephrine
53
Q

What is the pharmacology of Mepivacaine

A
  • concentration = 3%
  • amount of anesthetic = 30mg/ml
  • MRD = 4.4 mg/kg
  • maximum recommended does per appointment = 300mg
  • no vasoconstrictor in this concentration
54
Q

What is the pharmacology in Articaine

A
  • concentration = 4%
  • amount of anesthetic = 40mg/ml
  • MRD = 7 mg/kg
  • maximum recommended does per appointment = 500mg
  • dark grey label = 1:100,000 epinephrine
  • light grey label = 1:200,000 epinephrine
55
Q

How do you calculate the number of mg of anesthetic in a carpule?

A

concentration x volume x 10

56
Q

How do you calculate the number of carpules of anesthetic solution that can safely be used on an individual?

A
  1. determine the volume
    concentration x volume x 10
  2. check the MRD provided by manufacturer
  3. determine the weight of the client in kgs
  4. multiply the weight of individual by the MRD
  5. multiply that number to the volume of each carpule
57
Q

What factors besides weight can affect maximum allowable dosage of anesthetic

A
  1. age
  2. liver disease
  3. diabetes
  4. individual tolerance
  5. injection site vascularity
  6. general systemic health
  7. kidney disease
  8. presence of vasoconstrictor
  9. technique (aspiration)
58
Q

What is the law of local anesthetics

A

always use the lowest dose to achieve effective anesthesia

a local anesthetic alternative diphenhydramine - Benedryl

59
Q

Dental hygiene considerations review (be able to ask why each is important to check for learner’s understanding)

A
  • high degree of hypersensitivity to ester local anesthetic metabolites
  • most potent local anesthetic with greatest degree of lipid solubility is Bupivacaine
  • higher pKa = slower onset of drug action
  • recovery begins in molar teeth and ends with anterior teeth
60
Q

Dental hygiene considerations review (be able to ask why each is important to check for learner’s understanding)

A
  • degree of binding to receptor site determines speed of recovery
  • reinject anesthetic before mantel fibers have fully recovered
  • tachphylaxis is an increased tolerance to a repeatedly administered drug
  • local anesthetics are vasodilators
  • added vasoconstrictors counteract the vasodilatory properties of anesthetics
61
Q

Dental hygiene considerations review (be able to ask why each is important to check for learner’s understanding)

A
  • rate of systemic absorption depends on total dose, concentration, route of administration, vascularity of tissues, presence or absence of a vasoconstrictor
  • intravascular injection increases possibility of an overdose
  • local anesthetics affect CNS and CVS before biotransformation
  • local anesthetics cross blood-brain barrier
62
Q

Dental hygiene considerations review (be able to ask why each is important to check for learner’s understanding)

A
  • degree of toxicity depends on rate of absorption and elimination half-life
  • lower dosage for patients with liver dysfunction
  • lower dosage of prilocaine for patients with respiratory difficulties
  • articaine biotransformed in blood same as esters

Pharmacology Units 1-10 (13 decks)

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