Arai, Y.C., Matsubara, T., Shimo, K., Suetomi, K., Nishihara, M., Ushida, T., . . . Arakawa, M. (2010). Low-dose gabapentin as useful adjuvant to opioids for neuropathic cancer pain when combined with low-dose imipramine. Journal of Anesthesia, 24, 407–410.

To evaluate the effectiveness of low-dose gabapentin combined with imipramine, in treating cancer-related neuropathic pain

Patients were allocated to four groups. Group 1, consisting of 14 patients, received gabapentin 200 mg and imipramine 10 mg orally every 12 hours; Group 2, consisting of 14 patients, received gabapentin 200 mg orally every 12 hours; Group 3, consisting of 12 patients, received gabapentin 400 mg orally every 12 hours; and Group 4, consisting of 12 patients, received imipramine 10 mg orally every 12 hours. The average intensity of total pain over the past 12 hours was assessed, and the number of paroxysmal pain episodes in the past 24 hours were recorded. Pain was assessed at the first visit and seven days after the beginning of the regimen. Opioid rescue doses were available if needed.

• The sample consisted of 52 patients with solid tumors and neuropathic pain from nerve compression or spinal cord invasion.
• The mean age across groups was 65–69 years, range was 58–79 years.
• Men outnumbered women, 65% to 35%.

• Single-site outpatient setting
• Japan

Randomized, controlled trial

Pain was measured on a numeric scale, 1–10.

The total pain scores and daily paroxysmal pain episodes of the patients taking the low-dose gabapentin-imipramine combination (Group 1) decreased significantly (p < 0.05). The combination significantly decreased the previous 24-hour opioid rescue dose. Researchers observed mild adverse symptoms in all four groups. Symptoms included drowsiness, dizziness, and nausea. Note: Three patients dropped out of Group 3 because of adverse effects.

The combination of gabapentin and imipramine in low doses offers a means of successfully treating neuropathic pain, with minimal side effects.

• The small total sample size (< 100 participants) and the use of a single pain measurement scale are limitations.
• The results may not be reproduceable.
• Generalizing results to chemotherapy-induced neuropathic pain may be inappropriate.

The gabapentin-imipramine combination is effective in treating neuropathic pain caused by nerve compression or invasion of the spinal cord.