Local Anaesthetics

Question 1

Name the two (2) main classes of local anesthetics and provide an example of each

Answer 1

Esters: (more allergic - metabolized in blood) Procaine, Tetracaine, Cocaine
Amides: (metabolized in liver) - Fast onsetet. bupivacaine, lidocaine, ropivicaine, mepivacaine, levobupivcaine

Question 2

State two (2) ways of managing local anesthetic allergy.

Answer 2

ABCs, epinephrine, fluids

Question 3

What are the two chemical types of local anesthetics?

Answer 3

Amides (bupivocaine, lidocaine) and esters (procaine)

Question 4

Why do local anesthetics need hydrochloride salt to be added to them?

Answer 4

So that they can be injectable – LAs are all weak bases that require H+ (salt) to become stable and injectable.

Question 5

How do local anesthetics work?

Answer 5

They cause a reversible conduction blockade of nerve impulses by sodium channel blockade; this slows the rate of depolarization so threshold action potential is never reached.

Question 6

What are the important physiochemical properties of local anesthetics can influence their sites of action and duration of action? (just list them for now) (there’s 4)

Answer 6

lipid solubility, % ionization at a physiological pH, protein binding affinity, vasodilation properties

concentration of drug, volume of drug, route of administration, site of administration, adjuvants added (epinephrine), vascularization of the site.

Question 7

How will lipid solubility of an LA affect the site and duration of action?

Answer 7

Lipid solubility affects the potency; high lipid solubility leads to improved transit,

Question 8

How will pKa of an LA affect the site and duration of action?

Answer 8

Low pka=fast onset

pKA refers to ionization

Question 9

How will protein binding affect an LAs site and duration of action?

Answer 9

High protein binding results in a longer duration of action.

Question 10

How will vasodilation properties of LAs effect the site and duration of action?

Answer 10

The wider the vessels, the more able the drug is to be carried into the bloodstream.

Question 11

List the toxicities of local anesthetics (just list) (there are 4)

Answer 11

True allergy, neurotoxicity, systemic toxicity (CNS), cardiac toxicity

Question 12

Early warning signs of CNS toxicity?

Answer 12

numbness in tongue, tinnitus, lightheadedness, visual changes, ,muscle twitching, convulsions.

Question 13

What topical LAs can you use for needle phobia?

Answer 13

EMLA (slow) Ametop (fast)