Local Anesthetics

Question 1

Name the ester local anesthetics.

Answer 1

Benzocaine, Procaine, Cocaine

Question 2

Name the amide local anesthetics.

Answer 2

Lidocaine, Ropivacaine

Question 3

Describe the pharmacokinetic properties of of ester local anesthetics.

Answer 3

They have a short duration of action, are metabolized by the plasma and liver pseudocholinesterases, and are more prone to allergies because of derivatives produced by their metabolism.

Question 4

Describe the pharmacokinetic properties of amide local anesthetics.

Answer 4

They have a longer duration of action and are metabolized by P450 enzymes in the liver. They are less prone to allergy development.

Question 5

Describe the side effects from low systemic absorption of local anesthetics.

Answer 5

Disruption of sensory perception

Question 6

Describe the side effects of high systemic absorption of local anesthetics.

Answer 6

Anxiety, confusion, tremors, and convulsions if it enters the brain (secondary to blocking GABA-A receptors, tx with diazepam). Also causes depressed contractility, bradycardia, vasodilation, and hypotension. **Exception: cocaine

Question 7

Describe the adverse effects of cocaine.

Answer 7

Opposite CV side effects from other local anesthetics- causes tachycardia, htn, vasoconstriction

Question 8

Describe the mechanism of action of local anesthetics (benzocaine, procaine, cocaine, lidocaine, and ropivacaine)

Answer 8

They block activated and inactivated states of the VGSC (voltage-gated sodium channels), are use-dependent blockades.

Question 9

How is benzocaine used clinically?

Answer 9

Applied topically for EENT or dental conditions to reduce pain for minor procedures

Question 10

How is procaine used clinically?

Answer 10

It can be injected into skin, subcutaneous tissue, or mucous membranes (infiltration anesthesia), or for epidural or spinal anesthesia

Question 11

How is cocaine used clinically?

Answer 11

For dermal lacerations and ENT surgery, reducing pain of minor procedures (same as benzocaine)

Question 12

How is lidocaine used clinically?

Answer 12

For infiltration anesthesia (injection into skin, subcutaneous tissue, or mucous membranes), bier block (regional anesthesia w/ injection into vasculature), peripheral nerve block, epidural anesthesia, or spinal anesthesia

Question 13

Which local anesthetic requires an adjunct?

Answer 13

Lidocaine. It is given with epinephrine because when given alone it causes vasodilation.

Question 14

How is ropivacaine used clinically?

Answer 14

As a peripheral nerve block

Question 15

What is one advantage to using ropivacaine?

Answer 15

It is only synthesized in the S-isomer form, so it has a much lower affinity for cardiac Na+ channels, thus having fewer CV effects than the other local anesthetics

Question 16

Name the two types of pain fibers and how they differ in types of pain.

Answer 16

A-delta fibers are myelinated and are responsible for immediate, sharp pain response. C fibers are unmyelinated and are responsible for the later onset of dull, aching pain.

Question 17

What determines the potency of a local anesthetic?

Answer 17

Lipid solubility.

Question 18

What pKa (high or low) has a more rapid onset of action for local anesthetics?

Answer 18

Low pKa

Question 19

Name the local anesthetic agents.

Answer 19

Benzocaine, Procaine (aka Novacaine), Cocaine, Lidocaine, Ropivacaine