A Possible Role for Zonisamide in Treating Neuropathic Pain: A Case of Idiopathic Polyneuropathy

Anti-epilepsy medications have frequently beenused in the treatment of neuropathic pain to reduce thetransmission of nociceptive signals. 1,2 Zonisamide is a sulfona-mide drug that was approved in 2000 for the adjunctive treat- ment of partial seizures in adults. Because of the unique com-bination of mechanisms through which zonisamide functions,it has potential to be a useful option in the treatment of re-fractory neuropathic pain. We present the case of a patientwith refractory neuropathic pain related to idiopathic poly-neuropathy, who responded to adjunctive treatment withzonisamide. Key Words: anticonvulsants, sulfonamides, adjunctivetherapy CASE REPORT A 53-year-old female presented for evaluation of chronicpain associated with idiopathic sensorimotor neurop-athy. Her symptoms began in 1992 with constant burn-ing in her toes that gradually intensified and extendedproximally to her knees. The pain was lancinating inquality, was exacerbated by light touch and heat, andwas associated with numbness in a stocking distribu-tion. Her pain intensity was rated an average of 9 out of10 on a visual analog scale (VAS), where 0 is no pain,and 10 is the worst pain imaginable. Her past medicalhistory was positive only for hypertension. Prior to pre-sentation, she had undergone extensive diagnostic test-ing for peripheral neuropathy, which included screeningfor diabetes, HIV, ethanol, Lyme disease, connective tis-sue disorders, occult malignancy, and heavy metals, allof which were negative. She was found to have a mildlylow vitamin B