(635) The Advantages and Adverse Effects of Long‐Term Intrathecal Delivery of Opioid and Clonidine HCL Admixture

Intrathecal clonidine may be effective in neuropathic pain situations where large doses of opioids and local anesthetics or baclofen result in side effects and inadequate pain control. Addition of clonidine activates K (ATP) channels via a‐2 receptors. Clonidine administered intrathecally provides fourfold better pain control with lower side effects than systemic clonidine. Because clonidine does not interact with opioid receptors, it fails to cause opioid‐like side effects. Clonidine and opioids may have a synergistic efficacy. Materials & Methods: We performed a retrospective analysis of 23 patients, 10 male and 13 female, with a mean age of 55.4 years. Seventeen patients had neuropathic pain and 6 patients had mixed (neuropathic‐nociceptive) nonmalignant pain. They had failed to achieve satisfactory analgesia despite preclinical infusion of high dose morphine sulfate, hydromorphone HCL, or combinations of bupivacaine HCL/opioid or baclofen. The range of initiating daily dose of clonidine was 25 μg to 50 μg, to a maximum of 900 μg/day. The clonidine doses were titrated upwards to the end point of either efficacy or adverse effects. Clinical parameters studied were patient vital signs, pain intensity, pain relief, quality of sleep, drug intake, and side effects. Results: The preclonidine VAPS scores were on average 7.67 and the postclonidine VAPS scores were 5.82. Sleep improved for 50% of patients having poor to fair sleep. Length of therapy ranges from 1 month to 35 months with an average of 14.7 months of therapy. Of the 23 patients studied, 8 patients have been satisfied, coping with any side effects, and are still receiving mixed clonidine/opioid therapy. The side effects noted were nausea (9), sleepiness (8), dry mouth (7), dizziness (7), orthostatic hypotension (2), short term memory loss (2), headache (2), edema (2), depression (2), tinnitus (1), lethargy (1), nausea with vomiting (1), decreased energy (1), decreased libido (1), impotence (1), fine tremor (1), and anxiety (1). Conclusions: Intraspinal infusion of clonidine plus opioid may provide safer and better synergistic control of intractable neuropathic or mixed nonmalignant pain than pure intraspinal infusions of u‐opioid with local anesthetic.