Yelland, M.J., Poulos, C.J., Pillans, P.I., Bashford, G.M., Nikles, C.J., Sturtevant, J.M., . . . Brown, R. (2009). N-of-1 randomized trials to assess the efficacy of gabapentin for chronic neuropathic pain. Pain Medicine, 10, 754–761.

To determine whether gabapentin is more effective than placebo in regard to reducing pain, sleep interference, functional limitation, and the frequency of adverse events in patients with chronic neuropathic pain; to assess whether patients find gabapentin tolerable

The trial was offered to two groups of patients who had shown a clinical response to gabapentin: Three cycles of gabapentin and placebo treatment pairs were assigned in random order, with each treatment lasting two weeks. Dose was titrated to a maximum of 1,800 mg/day, depending on response and adverse effects. Rate of titration was 300 mg twice daily to start; dose increased by 300 mg/day. Breakthrough medications were, most commonly, opioids.

• Of the 112 enrolled patients, 39 dropped out due to nonresponses.
• Of all patients, 59% were women and 41% were men.
• Mean patient age was 57.6 years.
• The sample included these diagnoses: phantom limb pain, poststroke pain, post-therapeutic neuralgia, diabetic neuropathy, and complex regional pain syndrome.

The study was conducted at two hospitals in Australia.

Randomized, double-blind placebo-controlled crossover trial

• Visual analog scale (VAS), to measure pain and sleep interference
• Patient-Specific Function scale, to measure function
• VAS, to rate the degree that pain limited activities of daily living
• A checklist that listed symptoms that could be adverse events
• Global assessment of medication preference

Only 29% of participants showed a positive response to gabapentin. The ceiling dose of 1,800 mg, compared to 3,600 mg in other studies, may have reduced response rates. The participant withdrawal rate of 35% was high but fairly typical of n-of-1 trials.

Approximately 33% of patients responded to gabapentin, indicating that the drug may be fairly effective.

• No patients with cancer pain were included in the study.
• A fairly low ceiling dose may have limited the effectiveness of the drug.

The study findings were in line with other research that has shown gabapentin to be useful for patients with neuropathic pain. Approximately 33% of participants found gabapentin useful. However, applicability of findings to patients with cancer is unclear.