Sodium channel-blocking agents: Their use in neuropathic pain conditions

Neuropathic pain conditions are due to damage or permanent alteration of the peripheral or central nervous system. These conditions are generally chronic and less responsive to opiates than nociceptive (acute) pain conditions; as such, they are very difficult to treat clinically. Numerous classes of drugs, including opiates, antidepressants, anticonvulsants, local anesthetics, antiarrhythmics, steroids, antipsychotic agents, and topical capsaicin have been used to treat neuropathic pain. One mechanism common to several of these pharmacological agents is their ability to block sodium channels in a use-dependent fashion. In this focus article clinical evidence of the effectiveness of sodium channel-blocking drugs for relieving neuropathic pain will be presented. Experimental evidence for the site of action of these drugs will be discussed, along with future studies that are needed to develop new, more effective, agents.