Local Anesthetics Flashcards
Who first utilized cocaine as a local anesthetic?
Carl Koller and Sigmund Freud
They used it for tongue numbing and corneal anesthesia.
What are the main drawbacks of cocaine as a local anesthetic?
Significant toxicity, short duration, high cost, addiction
These factors limited its clinical use.
Who synthesized procaine?
Alfred Einhorn
Procaine was synthesized as a degradation product of cocaine.
What is the mechanism of action for local anesthetics?
Blockade of sensory information via sodium channels
Limited blockade occurs at potassium and calcium channels.
What is the general structure of local anesthetics?
Lipophilic substituted benzene ring linked to a hydrophilic amine group
This linkage is through either an ester or amide.
Name a few examples of amide local anesthetics.
- Lidocaine
- Prilocaine
- Mepivicaine
- Ropivicaine
- Bupivicaine
- Levobupivicaine
- Etidocaine
Amides are characterized by their specific chemical structure.
Name a few examples of ester local anesthetics.
- Cocaine
- Procaine
- 2-chloroprocaine
- Tetracaine
- Benzocaine
Esters differ in structure and certain properties from amides.
What is the pKa in relation to local anesthetics?
The pH at which the neutral and charged forms of the anesthetic occur equally
Lower pKa agents have a more rapid onset.
How does increased lipophilicity affect local anesthetics?
Slows rate of onset and prolongs duration of action
Increased protein binding also increases duration of action.
What is tachyphylaxis in the context of local anesthetics?
Tolerance does not occur if re-dosing occurs before pain
This phenomenon is important for managing pain.
What role does epinephrine play in local anesthesia?
Prolongation of local anesthetic block and decreased systemic absorption
It achieves this through vasoconstriction, slowing clearance from the injection site.
What is the typical ratio of epinephrine used with local anesthetics?
1:200,000
This ratio is commonly used to enhance the effects of local anesthetics.
How does alkalinization affect the onset of local anesthetics?
Shortens onset to blockade
Sodium bicarbonate can hasten blockade by 3-5 minutes.
What is the typical pH range of commercial local anesthetic solutions?
3.9-6.47
The pH is lower when epinephrine is present.
What is the effect of combining opioids with local anesthetics?
Synergistic analgesia when given neuraxially, except 2-chlorprocaine
This combination can enhance pain relief.
What are alpha2 agonists used for in local anesthesia?
Enhancing analgesic effects
They can be used in combination with local anesthetics.
