Ch 26: Local Anesthetics Flashcards
Group 1:
Low potency, short duration
- Procaine, chloroprocaine
purpose of local anesthetics
- to elicit loss of sedation in a discreet area
- reduce pain (analgesia)
- reduce nerve impulses (reflex sympathetic dystrophy syndrome)
peripheral nerve block
An injection close to nerve trunk (tooth extraction)
A type of regional anesthetic
transdermal
A route of administration that can increase penetration w/ iontophoresis or phonophoresis
(A patch used for medicine delivery)
sympathetic ganglion block
An anesthetic (injection in neck) that blocks the nerves along the spine
near a firing ganglion (for reflex sympathetic dystrophy syndrome)
central nerve block
Anesthetic (injection) into epidural or intrathecal space
Group 2:
Intermediate potency/ duration
- Lidocaine, mepivocaine
What are the two basic classes of local anesthetics
amino amides and amino esters
must have -caine suffix
What are the different classifications of local anesthetics?
Group 1
Group2
Group3
What are the different uses of local anesthetics?
topical transdermal infiltration anesthesia peripheral nerve block central nerve block sympathetic ganglion block
infiltration anesthesia
Anesthetic (injection) into tissue (repair skin laceration)
local anesthetics allow for what?
rapid recovery
lack of residual effects
little/no interference w/ CCV, respiratory, etc
Example’s of Local Anesthetics
- Benzocaine (pKa- 3.5)
* * enters tissues quickest (a good topical) - Mepivocaine (pKa- 7.7)
- Procainamide (pKa- 9.3)
- Lidocaine (pKa- 7.8)
Group 3:
High potency, long duration
- Bupivocaine, tetracaine
topical
skin, mucous membranes, cornea
spray on skin for hypertonic muscle (then exercise)
differential nerve block
tendency to anesthetize smaller fibers first (ex. pain fibers)
Ex: in labor, will block pain but not reduce uterine muscle tone or block contraction
goal of pharmacokinetics
produce analgesic w/o toxicity
discreet area effect (inject NEAR a nerve)
more on pharmacokinetics
- 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)
how do local anesthetics work?
- 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))
what are local anesthetics chosen for?
rate of onset
potency
duration of action
toxicity of local anesthetics
- potent ones LIKELY to cause toxicity
(have narrower therapeutic index) - can lead to convulsions by depressing central inhibitory fibers
