2005B03 Write brief short notes on the physicochemical properties of lignocaine.

Structure	· Lipophilic modified benzene ring, amide chain, terminal amine N(C2H5)2 · Achiral · Molecular weight 234g/mols
Behaviour	· Weak base o pKa 7.9 o ECF pH: 25% unionised o ICF pH: <10% unionised · Lipid solubility 150x procaine
Additives	· HCl: ↓pH -> ↑ionisation -> ↑solubility · Sodium metabisulfite: antioxidant/antibacterial (can cause hypersensitivity)
Formulation	· Aqueous solution for injection · Solution for spray onto upper airway · Topical gel · With prilocaine as EMLA