Neurotropin to Treat Chronic Neuropathic Pain

Study Summary

This study will examine the effectiveness of the drug neurotropin in treating chronic pain after injury to a limb or a large nerve. Two groups of patients will participate in this study: patients with complex regional pain syndrome type 1, or CRPS-I (also called reflex sympathetic dystrophy) and patients with complex regional pain syndrome type 2, or CRPS-II. CRPS-I is pain that develops after relatively minor injury to an arm or leg, but lasts much longer and is much more severe than would normally be expected. CRPS-II is pain resulting from injury to a large nerve. Candidates will have a history and physical examination, blood tests, and electrocardiogram. Participants will undergo the following tests and procedures: Patients with CRPS I and II will receive an individualized regimen of physical therapy and standard treatment to control their pain. In addition, they will receive neurotropin or placebo tablets for 5 weeks, then no trial medicine for at least 1 week, and then the other trial drug for the next 5 weeks. That is, patients who took placebo the first 5 weeks will take neurotropin the second 5 weeks and vice versa. Neither the patients nor the doctors will know who received which drug during the two intervals until the study is over. Patients will complete questionnaires about their pain, quality of life, and ability to perform daily living activities. They will have various tests to measure pain (such as sensitivity to heat and cold, to an electric current, to a mild pin prick, etc.); to provide information about changes in their condition (such as tests of range of motion of joints and limb size); to measure blood circulation and sweating in the arm or leg (such as measurements of blood flow to the limb, skin temperature, and sweat production), and other procedures.

Primary Outcome

Assessments of pain severity by the patient using a visual analogue scale ranging from 0 to 100 (mm), with 0 = no pain and 100 = maximal pain level. When it is difficult to recruit the patients, the interim analysis using these data is performed after completion of the study of first 16 patients (target number is 30). The data from 16 patients was analyzed while investigators were blinded to the treatment code (Drug A and B) provided by the NIH pharmacy. Only after the analysis was completed was

Interventions

• DRUG Placebo
• DRUG Neurotropin