Treatment that block pain transmission at the primary afferent level
Injection of anesthetic drugs like lidocaine blocks sodium channels at the nerve terminal and axon.
This blockade prevents depolarization and transmission of impulses. Another approach is to deplete substance P from the cutaneous nerve terminal with capsaicin.
This depletion does not completely prevent pain transmission but reduces pain sensitivity at the cutaneous field supplied by the primary afferent.
Fishman SM, Ballantyne JC, Rathmell JP (eds): Bonica’s management of pain, 4th ed. New York: Lippincott Williams & Wilkins, 2009.