Dextromethorphan Versus Placebo for Neuropathic Pain

Patients must be over 18 years of age. Patients must have a definite diagnosis of diabetic neuropathy or post herpetic neuralgia or a diagnosis of neuropathic pain of various etiologies other than diabetic neuropathy or post herpetic neuralgia. Duration of symptoms must be at least 3 months. Severity of pain must be at least mild, if constant; or at least moderate, if intermittent and at least 2 hours duration a day. Patients using tricyclics, narcotics, or antiseizure medications, must keep the drug dosages constant throughout the study. No patients with unstable disease process; i.e., angina pectoris, accelerated hypertension, recent stroke or transient cerebral ischemia, uncontrolled seizures. No pregnant or lactating women. Women of child bearing potential must use birth control pills, intrauterine device, or barrier contraceptive devices. No history of significant drug abuse or PCP use. No history of IV drug abuse, prescription drug abuse, or alcoholism. No significant liver or kidney disease. No MAO inhibitors. No cognitive impairment or language difficulty as judged by difficulty completing pain diary, medical history, or telephone conversation. Patients must not have any other chronic pain condition that gives them pain greater than the neuropathy pain.