A prospective open-label trial of gabapentin as an adjuvant analgesic with opioids for Japanese patients with neuropathic cancer pain.

BACKGROUND

Neuropathic pain is regarded as one of the main causes of cancer pain refractory to standard opioid therapy in palliative care. The use of adjuvant analgesics for neuropathic cancer pain is largely empirical and the true efficacy of these adjuvant analgesics has been unknown. Gabapentin is one of the new promising anticonvulsant drugs as an adjuvant analgesic for neuropathic cancer pain.

METHODS

The clinical usefulness of gabapentin in combination with opioids for Japanese patients with neuropathic cancer pain was assessed in an open-label, single-center, prospective study. Gabapentin was initiated in addition to the drugs currently being administered. The dose of gabapentin was titrated from 200 mg to a maximum dose of 2400 mg per day over 15 days, based on discussion with each patient. The primary endpoint variable was the numerical rating scale (NRS) of 0-10 measured using the brief pain inventory.

RESULTS

From February 2007 to December 2007, gabapentin was administered to 24 patients that were already receiving an opioid without sufficient analgesia. Administration of gabapentin statistically reduced the worst-NRS, the least-NRS, and the average-NRS (7.3 --> 5.8, 3.6 --> 3.0, 5.8 --> 4.5, respectively). Four patients (16.7%) were withdrawn from the study because of adverse events (headache, myoclonus, heartburn, bronchial asthma).

CONCLUSION

Although gabapentin might be regarded as a promising new adjuvant analgesic for neuropathic cancer pain, our results indicated that the decrease in pain score was of minimal clinical benefit. Controlled trials with other adjuvant analgesics are needed.