SAR of Local anaesthesia

SAR of Local anaesthesia

SAR of Local Anaesthesia shows how lipophilic group, intermediate chain, and amine group influence potency, duration, and activity.

1. Aromatic Group (Lipophilic End):

   • Typically, a benzene ring, responsible for lipophilicity, enabling penetration of nerve cell membranes.
   • Potency is proportional to lipid solubility, influencing membrane penetration.

2. Intermediate Chain (Linker):

   • Connects the aromatic group to the ionizable group and determines metabolism and duration of action.
   • Ester-linked Anesthetics:
     • Metabolized by plasma cholinesterases.
     • Higher risk of allergic reactions.
   • Amide-linked Anesthetics:
     • Metabolized in the liver.
     • Lower allergy risk and longer duration of action.

3. Ionizable Group (Hydrophilic End):

   • Usually a tertiary amine, contributing to hydrophilicity.
   • Degree of ionization affects onset of action:
     • Non-ionized form penetrates membranes.
     • Ionized form blocks sodium channels inside nerves, causing anesthesia.

Additional SAR Factors:

• Stereochemistry: Enantiomers may differ in activity and toxicity (e.g., bupivacaine).
• Intermediate Chain Length: Longer chains generally increase duration of action.
• Aromatic Ring Substituents: Lipophilic groups enhance potency, while hydrophilic groups may reduce it.

Thank you for reading from Firsthope's notes, don't forget to check YouTube videos!