Lec 8 - Local Anesthetics

Exam 1 - Dr. Castro

What South American plant did the first local anesthetics originate from?

Erythroxylum coca → Coca leaves

How did the native utilize coca leaves?

chew leaves → suppress hunger, fatigue, thirst, & pain

Local anesthetics act _______ to prevent the transmission of _______ in nerve fibers and other excitable tissues.

reversibly

electrical impulses

Why do myelinated fibers conduct electrical impulses faster than unmyelinated fibers?

saltatory conduction → action potential jumps between nodes of Ranvier

What are the advantages of local anesthetics?

can be used in conscious/ sedated patients

analgesia produced by local or regional effect

reduced opioid consumption/side effects

provide MAC (inhalant anesthetics) sparing effect

multimodal analgesia protocol

sustained analgesia during the recovery period

What are the clincial applications of local anesthetics?

topical

infiltration (intratesticular block)

splash blocks

intravenous regiona anesthesia (IVRA or Bier block) → large animal

soaker-type catheter

spinal & epidural anesthesia

peripheral nerve block

Local anesthetics work via voltage-gated _______ channels.

SODIUM

Local anesthetics are weak ______ meaning that they exist as an unionized _______ (B) and ionized ______ (BH) in equilibrium.

bases

lipophilic

hydrophilic

________ molecules cross the phospholipid neuronal membrane (main access)

unionized (lipophilic)

Inside the cell, _______ form binds to an open voltage-gates Na⁺ channels in a _______ & ________ manner. This ________ further neuronal transmission.

ionized (hydrophilic)

reversible & concentration dependent

prevents

The chemical structure of local anesthetics consists of what 3 components?

1. lipophilic benzene ring

2. hydrophilic amine group (3^o or 4^o amine)

3. intermediary chain → ester (-COO-) or amides (-CONH-)