Anaesthetics

Question 1

List the amide group LAs

Answer 1

Lidocaine
Mepivacaine
Bupivacaine
Etidocaine
Prilocaine

Question 2

List the ester group LAs

Answer 2

Cocaine
Procaine
Chloroprocaine
Tetracaine

Question 3

Why does bupivacaine have a long-acting property

Answer 3

Its hydrophobicity increases its likelihood of penetration through membranes

Question 4

Characteristics of amide group LAs

Answer 4

More prone to hydrolysis hence shorter duration of action
Metabolised in liver by microsomal cytochrome P450 isoenzymes
Excreted by kidneys

Question 5

Characteristics of ester group LAs

Answer 5

More likely to cause allergic reactions
Rapidly hydrolysed in blood by circulating butyrylcholinesterases into inactive metabolites, hence have very short plasma half-life

Question 6

Mechanism of action of LA

Answer 6

Bind to receptors near intracellular end of sodium channels to increase threshold for excitation while decreasing amplitude, frequency and impulse conduction.
The drug is administered parenterally, IM, in the proximity of the nerve such that it is able to reach the voltage gated sodium channels of the nerve.

Question 7

What does susceptibility of nerve fibers to blockade depend on?

Answer 7

• Smaller fiber diameter
• Faster firing frequency
• Fiber position on bundle (circumferential fibers are first to be exposed to LA)