Chapter 3 Flashcards
(34 cards)
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.
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.
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
If a person is allergic to one agent they are likely to what?
experience hypersensitivity to another agent in the same group
Cross-hypersensitivity between esters and amides is
Unlikely
ALL injectable local anesthetics manufactured for dentistry today are
Amides
Topical anesthetics are available in
Both esters and amides
What are two major routes of delivery for local anesthetic drugs?
- Topical
- Submucosal injection
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.
What happens during an infection?
Tissue acidity can impede the development of local anesthesia.
Acidic environment associated with what?
An active infection which causes a much lower pH in the vicinity of 5-6.
It is difficult to achieve what when an infection is present?
Dental anesthesia
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.
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
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
The process by which the local anesthetic moves from its extra neural site of deposition toward the nerve is called what?
Diffusion
The higher the concentration of administered local anesthetic
The more readily its molecule diffuse through the nerve, producing a more rapid onset of action.
The time interval between the initial deposition of the anesthetic solution at the nerve site until complete conduction blockade is call what?
Induction Time
When pain has returned after anesthetic was injected it is difficult to do what?
anesthetize again
It is important to do what before feeling comes back?
reinject the anesthetic before the mantel fibers have fully recovered.
What happens when increased tolerance to a drug that is administered repeatedly?
Tachyphylaxis
What affects the duration of anesthesia
- Vascularity of the injection site
- Presence or absence of a vasoconstrictor drug
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.
What do vasoconstrictors do?
- Reduces rapid systemic absorption
- Increases duration of the anesthetic
