Gabapentin effect on neuropathic pain compared among patients with spinal cord injury and different durations of symptoms

Study Design. This study evaluated the effect of gabapentin on neuropathic pain in patients with spinal cord injury. Objective. To compare the effect of gabapentin on neuropathic pain refractory to conventional analgesics in patients with spinal cord injury and different durations of symptoms. Summary of Background Data. Neuropathic pain in patients with spinal cord injury severely compromises their quality of life. Gabapentin is a new antiepileptic drug that may additionally have a role in the treatment of neuropathic pain. So far, there has been little prospective research investigating the effect of gabapentin on neuropathic pain in patients after spinal cord injury or comparing gabapentin-treated patients with varying durations of symptoms after spinal cord injury. Methods. The study included 31 patients who had experienced neuropathic pain associated with spinal cord injury or cauda equina syndrome. These subjects were divided into two groups. Group 1 (n = 13) was composed of patients whose duration of pain was less than 6 months, and Group 2 (n = 18) comprised patients whose symptoms of neuropathic pain had lasted more than 6 months. Although these patients had been treated with conventional analgesics such as antidepressants, anticonvulsants, membrane stabilizer, and neuroleptics, they reported that their condition did not improve after a medication trial of at least 2 weeks duration. In this study, conventional analgesics were continued at a therapeutic level, and gabapentin was administrated for an 18-day titration period followed by a 5-week maintenance period at a dosage of 1800 mg/day or the maximum tolerable dosage. The efficacy of gabapentin administration was gauged by a pain score and a sleep interference score using a 100-mm visual analogue scale (VAS) every 2 weeks. The scores of the two groups were compared every 2 weeks over the course of the 8-week study. Results. The mean pain score and the mean sleep interference score for Group 1 decreased more than that of Group 2 during the interval between 2 to 8 weeks (P < 0.05). The mean pain score for Group 1 decreased from 7.3 +/- 0.5, initially to 3 +/- 0.6 after 8 weeks of treatment, whereas the corresponding score for Group 2 decreased from 7.6 +/- 0.4 to 5.1 +/- 0.6 (P < 0.05). The mean sleep interference score for Group 1 decreased from 5.7 +/- 0.9 initially to 1.8 +/- 0.8 after 8 weeks of treatment, whereas the corresponding score for Group 2 decreased from 5.9 +/- 0.8 to 4.2 +/- 0.7 (P < 0.05). As compared with the onset of this study, a decrease in pain score of 2 or more was reported at the completion of this study for 11 patients (100%) in Group 1 and 10 (71%) of 14 patients in Group 2. A decrease of 2 or more in sleep interference scores was reported for 8 (89%) of 9 patients with sleep interference in Group 1 and for 8 (62%) of 13 patients with sleep interference in Group 2. Some adverse effects such as somnolence were noted, but they were mild or moderate in intensity. Conclusions. Gabapentin may be effective in decreasing neuropathic pain refractory to conventional analgesics in some patients with spinal cord injury whose duration of symptoms is less than 6 months, although those with duration of symptoms longer than 6 months showed a significant decrease as well. The drug is unlikely to cause serious adverse effects that limit its use in patients with spinal cord injury.