Ch 26: Local Anesthetics

Question 1

Group 1:

Answer 1

Low potency, short duration

- Procaine, chloroprocaine

Question 2

purpose of local anesthetics

Answer 2

• to elicit loss of sedation in a discreet area
• reduce pain (analgesia)
• reduce nerve impulses (reflex sympathetic dystrophy syndrome)

Question 3

peripheral nerve block

Answer 3

An injection close to nerve trunk (tooth extraction)

A type of regional anesthetic

Question 4

transdermal

Answer 4

A route of administration that can increase penetration w/ iontophoresis or phonophoresis

(A patch used for medicine delivery)

Question 5

sympathetic ganglion block

Answer 5

An anesthetic (injection in neck) that blocks the nerves along the spine

near a firing ganglion (for reflex sympathetic dystrophy syndrome)

Question 6

central nerve block

Answer 6

Anesthetic (injection) into epidural or intrathecal space

Question 7

Group 2:

Answer 7

Intermediate potency/ duration

- Lidocaine, mepivocaine

Question 8

What are the two basic classes of local anesthetics

Answer 8

amino amides and amino esters

must have -caine suffix

Question 9

What are the different classifications of local anesthetics?

Answer 9

Group 1
Group2
Group3

Question 10

What are the different uses of local anesthetics?

Answer 10

topical
transdermal
infiltration anesthesia
peripheral nerve block
central nerve block
sympathetic ganglion block

Question 11

infiltration anesthesia

Answer 11

Anesthetic (injection) into tissue (repair skin laceration)

Question 12

local anesthetics allow for what?

Answer 12

rapid recovery
lack of residual effects
little/no interference w/ CCV, respiratory, etc

Question 13

Example’s of Local Anesthetics

Answer 13

• Benzocaine (pKa- 3.5)
  * * enters tissues quickest (a good topical)
• Mepivocaine (pKa- 7.7)
• Procainamide (pKa- 9.3)
• Lidocaine (pKa- 7.8)

Question 14

Group 3:

Answer 14

High potency, long duration

- Bupivocaine, tetracaine

Question 15

topical

Answer 15

skin, mucous membranes, cornea

spray on skin for hypertonic muscle (then exercise)

Question 16

differential nerve block

Answer 16

tendency to anesthetize smaller fibers first (ex. pain fibers)

Ex: in labor, will block pain but not reduce uterine muscle tone or block contraction

Question 17

goal of pharmacokinetics

Answer 17

produce analgesic w/o toxicity

discreet area effect (inject NEAR a nerve)

Question 18

more on pharmacokinetics

Answer 18

• large volume will act quicker, but may not stay local
• low amount may not reach desired & efficacious concentration
• add vasoconstrictor to reduce diffusion (keeps drug local)

Question 19

how do local anesthetics work?

Answer 19

• bind to Na+ channels
  (to reduce action potentials of nerve conduction)
• bind to ACTIVE sodium channels
  (keep channel in a closed state)

** pKa of drug affects its rate of onset
cation (+) form is active
base forms transverse membrane
(more free base= quicker penetration (onset))

Question 20

what are local anesthetics chosen for?

Answer 20

rate of onset
potency
duration of action

Question 21

toxicity of local anesthetics

Answer 21

• potent ones LIKELY to cause toxicity
  (have narrower therapeutic index)
• can lead to convulsions by depressing central inhibitory fibers