Skip to main content
. 2006 Fall;53(3):98–109. doi: 10.2344/0003-3006(2006)53[98:EOLAP]2.0.CO;2

Figure 2.

Figure 2

Local anesthetic action. An injected local anesthetic exists in equilibrium as a quaternary salt (BH+) and tertiary base (B). The proportion of each is determined by the pKa of the anesthetic and the pH of the tissue. The lipid-soluble species (B) is essential for penetration of both the epineurium and neuronal membrane. Once the molecule reaches the axoplasm of the neuron, the amine gains a hydrogen ion, and this ionized, quaternary form (BH+) is responsible for the actual blockade of the sodium channel. Presumably, it binds within the sodium channel near the inner surface of the neuronal membrane.