Takahashi, H., & Shimoyama, N. (2010). A prospective open-label trial of gabapentin as an adjuvant analgesic with opioids for Japanese patients with neuropathic cancer pain. International Journal of Clinical Oncology, 15, 46–51.

To assess the usefulness of gabapentin in the treatment of cancer-related neuropathic pain

Patients who met the eligibility criteria of a score of 5 or greater on a numeric pain rating scale were entered. Gabapentin was begun at baseline at 200 mg and titrated to a maximum dose of 2,400 mg per day. Patients were asked to keep a pain diary and were assessed by a clinician throughout the 15-day study period.

• Twenty participants (10 men, 10 women) with a median age of 62 years (range of 31–74 years) were included in this study.
• Participants had a variety of tumor types, with the most common being colon and lung cancers.
• Of the total sample, 83% were inpatients, all were on opioids, 46% also were receiving nonsteroidal anti-inflammatory drugs, 79% were taking anticonvulsants, and 67% were on antidepressants.
• The range of the opioid dose was 6–600 mg.
• Fifty-four percent had pain from the tumor rather than from the treatment, and only 29% had actual peripheral neuropathy.

The study was conducted in a single-site inpatient setting in Japan.

This was an open-label, prospective study.

Measurements included a numeric pain rating scale using the Brief Pain Inventory, the McGill Pain Questionnaire, a numeric pain relief scale, and the Patient Global Impression of Change scale.

A significant reduction was noted at various time points for worst, least, and average pain on the numeric scale (p < 0.004). Mean change in scores from baseline ranged from 0.6 to 1.3. No differences were found in any other outcome measure.

A statistical reduction in pain occurred as measured on the five-point numeric rating scale; however, the change was relatively small.

• The study had a small sample size, with less than 30 participants.
• Neuropathic symptoms were found to be related to treatment in only 46% of patients in the study.
• Pain was measured by various means, but no direct measures were specific to neuropathy.
• No discussion took place as to whether there were any changes in analgesic regimens provided during the study.
• No appropriate control or comparison groups were used.

The study findings do not provide strong support for the effectiveness of gabapentin for the management of cancer-related neuropathic pain or other symptoms.