Local Anesthetics

Question 1

Amide and Ester drugs are what kind of drugs?

Answer 1

Local anesthetics

Question 2

What is the MOA of local anesthetics?

Answer 2

Bind to Na channels in nerve membranes slowing rate of depolarization

Question 3

T/F: Local anesthetics are weak bases

Answer 3

TRUE.

Question 4

What happens to local anesthetics in infected tissue sites?

Answer 4

When there is an infection in the tissue (acidic tissue due to infection) ionized portion of drug is increased causing less absorption of the drug into tissues.

Question 5

Potency, onset and duration of action are affected by what factors?

Answer 5

pK, protein binding and lipid solubility

Question 6

Lower pK, higher protein binding and higher lipid solubility will have what effect on the drug?

Answer 6

Faster onset, longer duration and higher potency

Question 7

Lidocaine, bupivacaine, mepivacaine and prilocaine are examples of which class of local anesthetics?

Answer 7

Amides

Question 8

What is the ONLY anesthetic drug used IV?

Answer 8

Lidocaine

Question 9

What are some systemic effects of Lidocaine?

Answer 9

Anti-arrhythmic, decrease MAC, analgesic, free radical scavenger, improve GI motility

Question 10

What amide has the highest CV toxicity?

Answer 10

Bupivicaine

Question 11

What amide is used for nerve blocks in equine patients due to the fast onset of action?

Answer 11

Mepivacaine

Question 12

Procaine, tetracaine/ proparacaine and benzocaine are examples of what class of local anesthetics?

Answer 12

Esters

Question 13

Which ester is used for ophthalmic procedures?

Answer 13

Proparacaine

Question 14

Which ester is used for laryngeal spray?

Answer 14

Benzocaine

Question 15

T/F: If epinephrine is administered, you will have decreased absorption of drugs.

Answer 15

TRUE-Epi causes vasoconstriction

Question 16

What route of administration allows for fastest absorption of local anesthetics?

Answer 16

Intercostal blocks-highest peak plasma concentration

Question 17

How are esters and amides metabolized?

Answer 17

Esters: hydrolysis by plasma cholinesterase
Amides: metabolized by microsomal liver enzymes-more likely to accumulate

Question 18

What drug allows for faster onset and prolonged duration and also helps by decreasing the sting upon injection?

Answer 18

Bicarbonate

Question 19

What effects will you have if you combine lidocaine and bupivacaine?

Answer 19

Shorten onset and lengthen DOA

Remember toxicity is additive, can’t use the MAX dose

Question 20

What drug combination causes severe methemoglobinemia in cats?

Answer 20

Benzocaine + tetracaine

Question 21

What is the most chondrotoxic and the least chondrotoxic drug?

Answer 21

Most: bupivacaine
Lease: Mepivacaine

Question 22

What mechanism do local anesthetics cause adverse CV reactions?

Answer 22

Block the Na channels

Question 23

If epinephrine is included, what initial signs will we see upon intravscular injection?

Answer 23

Increased HR

Question 24

What is the area with the highest absorption and the lowest absorption?

Answer 24

Intercostals > Epidural > brachial plexus

Question 25

Which LA commonly has allergic reactions?

Answer 25

Procaine in procaine penicillin G

Question 26

What fibers are blocked with LA that block pain?

Answer 26

A-delta and C fibers

Question 27

What are the 6 epidural contraindications? (CHINAS)

Answer 27

Coagulopathy
Hypovolemia
Infection at injection site
Anatomy
Sepsis