Local Anesthetics Flashcards
1
Q
Basic Structural Features of a LA
A
- benzene ring
- quaternary amine
- intermediate chain w ester or amide linkage
2
Q
Ester vs Amide Linkage
A
Ester - readily hydrolyzed
Amide - not hydrolyzed
LA with ester will be shorter acting
3
Q
Ionization
A
ionization is an equilibrium process that is reversible
4
Q
Ionization of a LA
A
5
Q
The predominating form of the LA is dependent on what?
A
The predominating form is dependent on the pKa of the amine and pH of the medium as described by the Henderson-Hasselbach equation:
6
Q
Lidocaine
A
- amide anesthetic.
- Metabolized by cytochrome P450 enzymes.
- The N- dealkylated metabolite retains activity.
- antiarrhythmic agent.
- pKa 7.6
7
Q
What amines are difficult to ionize?
A
Primary amines are difficult to ionize.
The most difficult form of an amine to ionize is a tertiary amine.
8
Q
Cocaine
A
- unique from other LA because it inhibits catacholamine uptake, particularly dopamine, at CNS synapses.
- hydrolyzed at both esters
- pKa 8.7
9
Q
Bupivacaine
A
- chiral carbon (As a consequence of a chiral center, optical isomeric forms of this local anesthetic are possible.)
- Marketed as a racemic mixture and as the levo isomer, levobupivacaine.
- long-acting amide
- pKa 8.1
10
Q
racemic
A
Bupivacaine is racemic - 50% of one isomer, 50% of another.
Levobupivacaine is an isomer
11
Q
Benzocaine - a LA outlier
A
- an exception to the basic quarternary amine local anesthetic structure.
- very short acting
- topical preparation
12
Q
A
Benzocaine
13
Q
A
Bupivacaine
14
Q
A
Cocaine
15
Q
A
Lidocaine
