A phase II study to establish the efficacy and toxicity of sodium valproate in patients with cancer-related neuropathic pain.

The efficacy and toxicity of sodium valproate for cancer-related neuropathic pain was evaluated in a phase II study at this cancer center. Twenty-five patients entered the study over a 13 month period. Pain was assessed using a pain scale based on the Brief Pain Inventory at days 0, 8 and 15. Nineteen patients completed the two week study period, one patient discontinued treatment because of toxicity, and five discontinued because of progressive disease. The most frequently observed side effects were drowsiness, unsteadiness, nausea, and decreased appetite. Response was defined as a decrease in pain score in the absence of increased need for analgesic medication. The response rate for average pain at day 15 in assessable patients was 55.6% (30.8-78.5%, 95% CI), but response rates varied considerably depending on the mode of analysis. Baseline efficacy data have been gained on which to base future comparative studies against antidepressants.