EPIDURAL CLONIDINE ANALGESIA FOR INTRACTABLE CANCER PAIN

Although the vast majority of patients with cancer pain receive effect ive analgesia from standard therapy, a few patients, particularly thos e with neuropathic pain, continue to experience severe pain despite la rge doses of systemic or intraspinal opioids. Animal studies suggest i ntraspinal alpha(2)-adrenergic agonists may be effective in such cases . Eighty-five patients with severe cancer pain despite large doses of opioids or with therapy-limiting side effects from opioids were random ized to receive, in a double-blind manner, 30 mu g/h epidural clonidin e or placebo for 14 days, together with rescue epidural morphine. Pain was assessed by visual analog score (VAS), McGill Pain Questionnaire, and daily epidural morphine use. Success was defined as a decrease in either morphine use or VAS pain, with the alternative variable either decreasing or remaining constant. Blood pressure, heart rate, and deg ree of nausea and sedation were monitored. Successful analgesia was mo re common with epidural clonidine (45%) than with placebo (21%). This was particularly prominent in those with neuropathic pain (56% vs. 5%) . Pain scores were lower at the end of the treatment period in patient s with neuropathic pain treated with clonidine rather than placebo, wh ereas morphine use was unaffected. Clonidine, but not placebo, decreas ed blood pressure and heart rate. Hypotension was considered a serious complication in 2 patients receiving clonidine and in 1 patient recei ving placebo. This study confirms the findings from previous animal st udies which showed the effective, potent analgesic properties of intra spinal alpha(2)-adrenergic agonists and suggests that epidural clonidi ne may provide effective relief for intractable cancer pain, particula r of the neuropathic type.