How do Local Anesthetics work?

How do Local Anesthetics work?

• A. Block K+ Channels
• B. Activate Na+ Channels
• C. Activate Calcium Channels
• D. Block Na+ Channels

Answer: (D)

Local anesthetics work by reversibly blocking voltage-gated sodium channels in nerve membranes. They cross the nerve membrane in an uncharged form, then inside the cell become ionized and bind to the inner portion of the sodium channel, preventing Na+ entry during depolarization. Without sodium influx, the action potential cannot propagate along the nerve, so sensory signals, including pain, are not transmitted. The blockade is stronger in small, myelinated pain fibers and is use-dependent, meaning active fibers are blocked more readily. Tissue acidity can reduce effectiveness because it lowers the amount of uncharged drug that can cross the membrane. They produce their effect by targeting sodium channels, not potassium or calcium channels.

Local anesthetics work by reversibly blocking voltage-gated sodium channels in nerve membranes. They cross the nerve membrane in an uncharged form, then inside the cell become ionized and bind to the inner portion of the sodium channel, preventing Na+ entry during depolarization. Without sodium influx, the action potential cannot propagate along the nerve, so sensory signals, including pain, are not transmitted. The blockade is stronger in small, myelinated pain fibers and is use-dependent, meaning active fibers are blocked more readily. Tissue acidity can reduce effectiveness because it lowers the amount of uncharged drug that can cross the membrane. They produce their effect by targeting sodium channels, not potassium or calcium channels.