Gabapentin for the treatment of chronic intractable neuropathic pain: a long-term follow-up study

Abstract

Aim of Investigation: Neuropathic pain is caused by functional abnormalities or structural lesions in the peripheral or central nervous systems, and occurs without peripheral nociceptor stimulation. The treatment of neuropathic pain is difficult and done in a variety of ways. This long-term follow-up clinical study investigates efficacy and safety of gabapentin in reducing chronic intractable neuropathic pain, with patients who are resistant to current analgesic treatment regimens or conventional pain therapies. Methods: The investigation was carried out between May 2001 and November 2004. The duration for follow-up of our study was 2 to 43 months. Efficacy was evaluated using four verbal ranking scales, 0–10 for pain intensity, 0–3 for mood profile, 0–3 for quality of sleep, and 0–4 for activity (Eastern Cooperative Oncology Group Scale). Measurements were taken before and after each treatment. Pain quality was assessed with the McGill Pain Questionnaire. Adverse effects and satisfaction (0–4 level scale) were also recorded. Data were analyzed by paired Student's t-test with p < 0.05 considered statistically significant. Results: The 58 enrolled Chinese patients (female: 37, male: 21) had a mean age of 67.2 years (range 45–86) and a history of neuropathic pain unresponsive to conventional medicine. Previous duration of pain was 3 months to 16 years (mean 29.2 ± 41.7 months). Significant improvement (p < 0.0001) was found in initial versus final estimations of pain (9.67 ± 0.96 vs 3.01 ± 1.84), interference of mood (2.5 ± 0.76 vs 0.55 ± 0.54), quality of sleep (2.38 ± 0.99 vs 0.45 ± 0.65), daily activity (1.62 ± 1.14 vs 0.59 ± 0.77), and overall satisfaction with results (3.7 ± 0.53). No significant adverse effects were found when combining gabapentin with amitriptyline (n = 44, 76%) and/or tramadol (n = 24, 41%). Final daily doses were gabapentin 584.5 ± 361.7 mg (range: 100–1800 mg), amitriptyline 27.6 ± 11.9 mg (range: 10–75 mg) and tramadol 216.7 ± 120.4 mg (range: 100–600 mg). Long-term follow-up found these results to continue for 2 to 43 months (9.7 ± 10.9 months). The most frequent adverse effects were dizziness (28%), somnolence (19%) and ataxia (9%). Conclusions: Treatment with gabapentin at low clinical doses combined with low doses of amitriptyline and/or tramadol was found to effectively and safely treat chronic intractable neuropathic pain with few side effects.