Local Anesthetics – Mechanism, Classes, Toxicity and vasoconstrictors PPT

June 28, 2012 | By | Reply More

Local Anesthetics –  Mechanism, Classes, Toxicity and vasoconstrictors PPT

powerpoint lecture slide

Local Anesthetics- History

•1860 – cocaine isolated from erythroxylum coca
•Koller – 1884 uses cocaine for topical anesthesia
•Halsted – 1885 performs peripheral nerve block with local
•Bier – 1899 first spinal anesthetic
Local Anesthetics – Definition

A substance which reversibly inhibits nerve conduction when applied directly to tissues at non-toxic concentrations

Local anesthetics – Mechanism

Limit influx of sodium, thereby limiting propagation of the action potential.

Local Anesthetics – Classes












Local anesthetics – Formulation

Biologically active substances are frequently administered as very dilute solutions which can be expressed as parts of active drug per 100 parts of solution (grams percent)


Ex.:   2% solution  =

_2 grams__   =   _2000 mg_   =   __20 mg__

100 cc’s              100 cc’s                1 cc


Local Anesthetics – Allergy

•True allergy is very rare
•Most reactions are from ester class – ester hydrolysis (normal metabolism) leads to formation of PABA – like compounds
•Patient reports of “allergy” are frequently due to previous intravascular injections
Local Anesthetics – Toxicity

Tissue toxicity – Rare

•Can occur  if administered in high enough concentrations (greater than those used clinically)
•Usually related to preservatives added to solution

Systemic toxicity – Rare

•Related to blood level of drug secondary to absorption from site of injection.
•Range from lightheadedness, tinnitus to seizures and CNS/cardiovascular collapse
Local anesthetics – Duration
•Determined by rate of elimination of  agent from site injected
•Factors include lipid solubility, dose given, blood flow at site, addition of vasoconstrictors (does not reliably prolong all agents)
•Some techniques allow multiple injections over time to increase duration, e.g. epidural catheter
Local anesthetics – vasoconstrictors


Epinephrine is added to local anesthetics in extremely  dilute concentrations, best expressed as a ratio of grams of drug:total cc’s of solution. Expressed numerically, a 1:1000 preparation of epinephrine would be

Vasoconstrictors should not be used in the following locations

•Ear lobes


Category: Dental, Medical

WARNING: Any unauthorised use or reproduction of  www.neuronarc.com content for commercial or any purposes is strictly prohibited and constitutes copyright infringement liable to legal action.