Systemic lidocaine silences ectopic neuroma and DRG discharge without blocking nerve conduction.

Systemic application of lidocaine in rats suppressed ectopic impulse discharge generated both at sites of experimental nerve injury and in axotomized dorsal root ganglion (DRG) cells. ED50 for DRGs was significantly lower than for the injury site. Lidocaine doses effective at blocking ectopic discharge failed to block the initiation or propagation of impulses by electrical stimulation, and only minimally affected normal sensory receptors. This selectivity may account for the effectiveness of systemic local anesthetics and other drugs that share the same mechanism of action (notably certain anticonvulsants and antiarrhythmics), in the management of neuropathic paresthesias and pain. In addition, it may account for the prolonged analgesia sometimes obtained using regional local anesthetic block.