Local anaesthetics

摘要

LAs reversibly block neuronal transmission and stabilise electrically excitable membranes. They exist in two states: acidic (ionised) and basic (non-ionised). There are two mechanisms of action:Blockade of Na~+ channels: Unionised, lipid-soluble drug passes through the phospholipid membrane (charged molecules do not cross the cell membrane). It becomes ionised and binds to the intracellular surface of fast Na~+ channels, preventing further depolarisation.Membrane expansion: Unionised drug dissolves into the phospholipid membrane, expanding and disrupting the Na~+ channel/lipoprotein matrix causing inactivation.