Local Anesthetic Flashcards
What distinguishes the acid form from the basic form?
Acid form has a proton that is lacking in basic form
T/F: The acidic form will always have a positive charge.
False
Charge will be more positive than basic form but one can be neutral
What is the acid/base distribution of dibucaine in the body? What is significance?
50% of each
Need both.
Acid - blocks axonal conduction
Base - allows it to cross neuronal membrane
What are the three parts of local anesthetic?
Aromatic group and amine group linked by an ester or amide linkages
T/F: Ester linkages break apart more easily than amide linkages.
True
Ester - oxygen
Amide - Nitrogen
T/F: Local anesthetic will cross membranes in the brain.
True
T/F: Ester linked anesthetics are more susceptible to allergies.
True
What type of anesthetic (ester or amide) is used in dentistry?
Amides
Not worried about getting into bloodstream and amides are less likely to develop me allergies
LA with an amide linkage are metabolized by _______ in the liver and have a ___________ half life in the plasma.
P450; longer
How can you recognize an amide LA versus an ester based on nomenclature?
Amides will have an “i” before the “caine”
Ex. Lidocaine
What form of LA crosses the cell membrane?
Uncharged basic form
What form of the LA will block axonal conductance?
Charged acidic form bonds to Na channel
When can LA not interact with the Na channel?
When it is in the resting state
Can interact with open and inactivated
T/F: Anesthetic will act on a nerve that is not firing.
False
Cannot act on resting state of channel
T/F: Pain receptors are easier to inactivate with LA than motor neurons.
True
Thinner nerves are easier to inactivate
What are the two classes of pain neurons?
A delta - myelinated, fast pain, cold
C fibers - not myelinated, slow pain, hot
T/F: Rapidly firing nerves are more susceptible to LA.
True
In what order will nerve functions be lost?
- Pain
- Cold
- Warmth
- Touch
- Deep pressure
Come back in reverse order
T/F: Inflamed tissue is more difficult to anesthetize.
True
Inflammatory products lower the pH -> make it harder for LA to get in the axon (less basic form of LA)
T/F: If a LA is more lipid-soluble it will be shorter acting.
False
Hydrophilic will help it diffuse to site, but the more lipid soluble = the less quickly it gets cleared
Lipid soluble = longer acting
What effects can LA have on the heart?
Block Na channels and Ca channels (Ca at very high concentrations)
Which LA is especially cardiotoxic?
Bupivacaine
For use in pregnancy, what are the classes of most LAs?
B and C
T/F: Fatalities during dental LA are very low.
True
