Pharmacology

Local anesthesia

Local anesthesia

  • Local anesthesia is the reversible loss of sensation in a particular are of the body caused nerve ending depression or inhibit peripheral nerve conduction.

Types of anesthesia

  1. Surface anesthesia  
  2. Infiltration anesthesia  
  3. Epidural anesthesia  
  4. Spinal anesthesia  

1. Surface anesthesia  

  • It produce by locally only topical action and there is no loss of motor function.
  • Example: Lidocaine in throat acts in 2-5 min and produced anesthesia for 30-45 min.

2. Infiltration anesthesia  

  • LA anesthesia (dilution solution) administered under the skin at the operation area.
  • Immediate onset of action, duration of action – shorter than the nerve block.
  • Example: Lidocaine – 30 – 60 min. Bupivacaine – 120 -180 min.

3. Conduction block

  • The LA is injected around nerve trunks so that the area distal to injection is anaesthetized and paralyzed.

4. Spinal anesthesia   

  • It blocks the pain in a particular region.
  • Epidurals block the nerve impulses from the lower spinal segments.
  • This results decreased sensation in the lower half of the body.

Classification

A. Injectable anesthesia  

  1. Low potency, short duration

Example: procaine, chlorprocaine

2. Intermediate potency and duration

Example: lidocaine (Lignocaine), Prilocaine

3. High potency, long duration

Example: tetracaine, bupivacaine, ropivacaine dibucaine (cinchocaine)

B. Surface anesthesia  

            Soluble:

                        Example: cocaine, lidocaine, tetracaine, benoxinate

            Insoluble:

                        Example: benzocaine, butylaminobenzoate (Butamben)

C. Ester – linked Las

            Example: cocaine, procaine, chlorprocaine, tetracaine, benzocaine

D. Amino – linked Las

            Example: Lidocaine, bupivacaine, dibucaine, prilocaine, ropivacaine.

Mechanism of action

  • M-gate and “h” gate (halt gate) is present at the extra and intra cellular mouth of the membrane.
  • The gates are closed in the resting state.
  • Threshold depolarization of the membrane opens the activation gate allowing Na+ ions.
  • The local anesthetics receptor is located within the channel in its intracellular half.
  • The unionized form of local anesthetics traverses the membrane.
  • Re-ionized in the axoplasm and binds at the LA receptor.
  • The cationic form (BH+) of the local anesthetics which primarily binds to the receptor.
  • The LA receptors are more affinity, so more accessible of LAs, thus reduce the opening of channels and Na+ ions does not enter.

Hello! My name is Smrutiranjan Dash, a pharmacy professional. belonging from, Bargarh, Odisha. I have acquired Master degree in Pharmacy (Pharmacology) form B.P.U.T, Rourkela, Odisha. Presently I am working as an Assistant Professor at The pharmaceutical college, Barpali.

Leave a Reply

Your email address will not be published. Required fields are marked *

', 'auto'); ga('send', 'pageview');