Flashcards in Chapter 3 Deck (34)
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1
How do local anesthetics work?
They are agents that block the sensation of pain by reversibly blocking nerve conduction when applied to a circumscribed area of the body.
2
Local Anesthetics Mechanism of Action
-Blocking the conduction of a nerve impulse by preventing the nerve from reaching its firing potential
-Bind to specific receptors in the nerve membrane to prevent the influx of sodium ions through cell membrane.
3
What are properties if the ideal local anesthetic?
-Potent
-reversible
-Absence of local reaction
-Absence if systemic reaction
-Absence of allergic reaction
-rapid onset
-Satisfactory duration
-Adequate tissue penetration
-low cost
-Stability in solution (long shelf life)
-Ease of metabolism and excretion
4
If a person is allergic to one agent they are likely to what?
experience hypersensitivity to another agent in the same group
5
Cross-hypersensitivity between esters and amides is
Unlikely
6
ALL injectable local anesthetics manufactured for dentistry today are
Amides
7
Topical anesthetics are available in
Both esters and amides
8
What are two major routes of delivery for local anesthetic drugs?
-Topical
-Submucosal injection
9
What does pka represent?
the PH at which 50% of the molecules exist in the lipid-soluble tertiary form and 50% in the quaternary, water-soluble form.
10
What happens during an infection?
Tissue acidity can impede the development of local anesthesia.
11
Acidic environment associated with what?
An active infection which causes a much lower pH in the vicinity of 5-6.
12
It is difficult to achieve what when an infection is present?
Dental anesthesia
13
Anesthetic buffering provides what?
the practitioner a way to neutralize the anesthetic immediately before the injection in vitro (outside the body) rather than the in vivo buffering process, which relies on the patient's physiology to buffer anesthetic.
14
Anesthetics that have a low degree of lipid solubility, that are catatonic, and ionized will penetrate the nerve membrane slowly and have a what?
Slower onset
15
Anesthetics that have high degree of lipid solubility and are in the base un-ionized form will readily cross the nerve membrane and attach to the sodium receptors have what?
Rapid onset
16
The process by which the local anesthetic moves from its extra neural site of deposition toward the nerve is called what?
Diffusion
17
The higher the concentration of administered local anesthetic
The more readily its molecule diffuse through the nerve, producing a more rapid onset of action.
18
The time interval between the initial deposition of the anesthetic solution at the nerve site until complete conduction blockade is call what?
Induction Time
19
When pain has returned after anesthetic was injected it is difficult to do what?
anesthetize again
20
It is important to do what before feeling comes back?
reinject the anesthetic before the mantel fibers have fully recovered.
21
What happens when increased tolerance to a drug that is administered repeatedly?
Tachyphylaxis
22
What affects the duration of anesthesia
-Vascularity of the injection site
- Presence or absence of a vasoconstrictor drug
23
What affects the absorption of Local Anesthesia?
-Total does and concentration of the administered drug.
-Route of Administration
-Vascularity of the tissue at the administration site.
-Presence or absence of vasoconstrictor.
24
What do vasoconstrictors do?
-Reduces rapid systemic absorption
-Increases duration of the anesthetic
25
Highly vascular organs have what?
higher concentrations of anesthetics.
26
Toxicity is directly related to what?
the amount of anesthetic accumulation in tissue.
27
What is elimination half-life?
The period of time it takes for 50% of the drug to be metabolized/removed from the body.
28
What is the primary excretory organ for Local anesthetics?
Kidneys
29
Small percentage excreted is what?
unchanged in the urine
30
Esters are what during excretion?
almost completely hydrolyzed in blood
31
What are excreted in small amounts in urine?
Esters
32
What do you need to consider before giving anesthetics?
patients with renal disease will accumulate the anesthetic in their kidneys
33
Systemic Effects of Local anesthetics are directly related to what?
-Nature of drug
-Concentration of the drug and does administered
-Route of administration
-Rate of injection
-Vascularity in area of injection
-Age of patient
-Weight of patient
-Health of patient
-Route and rate of metabolism and excretion of drug.
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