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Local Anesthesia > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

What makes LA different from other drugs used in medicine and dentistry?

A

Local anesthetics stop providing clinical effects once they enter the circulation
- We don’t want to inject dental LA into the bloodstream

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2
Q

What is the termination of action of LA?

A

Redistribution from nerve to CVS

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3
Q

What does it mean to have LA in circulation?

A

Drug can exert effects on other cells in the body

- Detrimental effects

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4
Q

LA injected into soft tissues = What?

A

Local effect on blood vessels in area

- VASODILATORY effect

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5
Q

Which is the most potent vasodilator?

A

Procaine (ester)

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6
Q

Which is the only local anesthetic that produces vasoconstriction?

A

Cocaine

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7
Q

How does cocaine work?

A

Prohibits uptake of catecholamines (especially norepinephrine) into tissue binding sites
- Prolonged, intense vasoconstriction

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8
Q

What is the significance of the vasodilatory effect of LA?

A

Increases rate of absorption into the blood

  • Decreases duration and quality of pain control
    • -> Anesthetic gets carried away from site of administration
  • Increases blood concentration of anesthetic and potential for overdose (toxicity)
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9
Q

Routes of administration for LA

A

Oral route = poorly absorbed from GI tract (except for cocaine)
Topical route = different rates of absorption on mucous membranes
Parenteral route = injection
–> in dentistry: subcutaneous injection

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10
Q

How is LA distributed?

A

Once in bloodstream, LA distributed throughout the body to all tissues

  • Highly perfused organs obtain higher blood levels of LA
  • Skeletal muscle contains greatest percentage of LA (largest mass of tissue in body) even though not as highly perfused.
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11
Q

T or F, LA readily crosses blood-brain barrier but not placenta

A

False, both

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12
Q

blood level of the LA is determined by what:

A
  1. Rate of absorption into CVS
  2. Rate of distribution from vascular compartment to the tissues
    • Healthier people can redistribute the drug more quickly, leading to lower blood levels
  3. Elimination of drug through metabolic or excretory pathways
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13
Q

LA follows what elimination kinetics?

A

First order kinetics

- drug is removed in 4 to 5 half-lives

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14
Q

T or F, Metabolism of esters and amides occur in a similar manner

A

False, they differ

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15
Q

Describe the biotransformation of esters

A

Hydrolyzed in the blood by plasma cholinesterase

- also called cholinesterase and pseudocholinesterase

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16
Q

What is the metabolic byproduct of esters being hydrolyzed by cholinesterase?

A

PABA - paraminobenzoic acid

  • This triggers allergy
  • Excreted in urine
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17
Q

What is Atypical Pseudocholinesterase?

A

Inherited disorder

  • Unable to hydrolyze ester local anesthetics and related drugs
  • Prolongation of higher LA blood levels = risk for toxicity
  • **Relative contraindication to use of ester local anesthetics
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18
Q

Describe the biotransformation of amides

A

Metabolized in liver

-

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19
Q

Describe the role of liver function in biotransformation of amides

A

Liver function and hepatic perfusion influence rate of biotransformation

  • Liver disease
  • Lower than usual hepatic blood flow (hypotension, congestive heart failure)
  • ->both lead to slower rates of biotransformation, increased anesthetic blood levels = risk for toxicity
20
Q

Name the contraindications for both amides and esters

A 
Amides = significant liver dysfunction or heart failure
Esters = Atypical pseudocholinesterase
21
Q

T or F, rates of biotransformation of amides are relatively similar

A

True

- lidocaine, mepivacaine, artisane, and bupivacaine

22
Q

Where does prilocaine undergo metabolism

A

Primary metabolism in liver, with some also in lung

23
Q

What is the primary metabolite in prilocaine

A

Orthotoluidine = primary metabolite

  • induces the formation of methemoglobin
  • leads to methemoglobinemia
24
Q

What are the metabolites in Lidocaine?

A

monoethylglycinexylidide
glycine xylidide
–> may be responsible for producing sedation

25
Q

What organs excrete LA and metabolites

A

Kidneys

- percentage varies by drug

26
Q

Between amides and esters, which appears in greater percentage ?

A

Amides are present in urine as a parent compound in greater percentage than esters (but still small amount)
- esters apear in very small concentrations in urine (almost completely metabolized in plasma)

27
Q

What disease is a relative contraindication to LA?

A

Renal disease

28
Q

Systemic actions of local anesthetics are related to what?

A

Blood/plasma level

29
Q

Pharmacological effect of LA

A

CNS depression.

  • Therapeutic doses –> no CNS effects
  • Overdose/toxicity –> generalized tonic-clonic convulsions (INHIBIT inhibition = SEIZURE)
30
Q

LA can also be used to treat what?

A

Epilepsy

  • Some LA have anticonvulsant properties
  • Blood level is lower than that which produces seizures
31
Q

Describe the CVS effects of LA

A

direct actions on myocardium and peripheral vasculature

  • Pharmacological action = myocardial depression
    • -> decrease electrical excitability of myocardium
    • -> decrease conduction rate (negative chronotropic effect)
    • -> decrease force of contraction (negative inotropic effect)
32
Q

Lidocaine is used how in CVS

A

As an anti-arrhythmic medication

33
Q

Describe systemic effects of LA being a vasodilator

A
  1. increases blood flow to/away from site of deposition
  2. increases rate of LA absorption
  3. Decreases depth and duration of anesthesia
  4. Increases bleeding
  5. Increases LA levels in circulation
34
Q

T or F, LA effect on blood pressure = hypertension

A

False, hypotension –> they are vasodilators

35
Q

Describe CVS effects at Non-overdose levels of LA

A

Slight increase or no change in BP due to increased CO and HR; vasoconstriction of some vascular beds

36
Q

Describe CVS effects when approaching overdose levels of LA, but still below

A

Mild hypotension (direct relaxant action on vascular smooth muscle)

37
Q

Describe CVS effects at overdose levels of LA

A

PROFOUND HYPOTENSION

- caused by decreased myocardial contractility, decreased CO and decreased peripheral resistance

38
Q

Describe CVS effects at lethal levels of LA

A

CARDIOVASCULAR COLLAPSE

- Massive peripheral vasodilation, decreased myocardial contractility and decreased HR (sinus bradycardia)

39
Q

Bupivacaine may produce what at overdose levels

A

Fatal ventricular fibrillation

40
Q

What tissue is more sensitive to irritating properties of LA than other tissues?

A

Skeletal muscle

41
Q

Respiratory System effects at non-overdose levels

A

Direct relaxant action on bronchial smooth muscle

42
Q

Respiratory system effects at overdose levels

A

Respiratory arrest due to generalized CNS depression

43
Q

T or F, Therapeutic dosing produces effects similar to non-overdose levels

A

False, does not produce any significant effects on respiratory function

44
Q

Describe how LA can help cause neuromuscular blockage

A

Additive effects when LA is used with other depolarizing and non-depolarizing muscle relaxants (not typical in a dental patient)

45
Q

When combined with a certain genetic variant, LA can increase an individual’s susceptibility to this disorder

A

Malignant hyperthermia

Local Anesthesia (3 decks)

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