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Administering drugs into the intrathecal space is becoming more popular in the treatment of patients with intractable pain or intolerable side effects of systemic analgesic treatments. Although morphine and ziconotide are the only intrathecal analgesics currently approved by regulatory authorities in the U.S. (Food and Drug Administration) and Europe (national-level approval by individual countries for morphine and European Agency for the Evaluation of Medicinal Products approval for ziconotide), a wide variety of opioid and non-opioid drugs are being used in this way. There is no official guidance concerning the selection of these drugs or their use in combinations and a paucity of efficacy and safety data from randomized controlled trials. The polyanalgesic initiative aims to summarize the current knowledge and to facilitate rational choices of intrathecal drug and drug combinations for the management of chronic pain. The most recent polyanalgesic consensus recommendations were published in 2007. In this review, we shall examine these recommendations, which are tailored toward those practicing intrathecal analgesia in the U.S., and discuss how they should be implemented in Europe, where the healthcare systems and regulations of the medical authorities are different.

Chronic pain may recur after initial response to strong opioids in both patients with cancer and patients without cancer or therapy may be complicated by intolerable side effects. When minimally invasive interventional pain management techniques also fail to provide satisfactory pain relief, continuous intrathecal analgesic administration may be considered. Only 3 products have been officially approved for long-term intrathecal administration: morphine, baclofen, and ziconotide. The efficacy of intrathecal ziconotide for the management of patients with severe chronic refractory noncancer pain was illustrated in 3 placebo-controlled trials. A randomized study showed this treatment option to be effective over a short follow-up period for patients with pain due to cancer or AIDS. The efficacy of intrathecal opioid administration for the management of chronic noncancer pain is mainly derived from prospective and retrospective noncontrolled trials. The effect of intrathecal morphine administration in patients with pain due to cancer was compared with oral or transdermal treatment in a randomized controlled trial, which found better pain control and fewer side effects with intrathecal opioids. Other evidence is derived from cohort studies. Side effects of chronic intrathecal therapy may either be technical (catheter or pump malfunction) or biological (infection). The most troublesome complication is, however, the possibility of granuloma formation at the catheter tip that may induce neurological damage. Given limited studies, the evidence for intrathecal drug administration in patients suffering from cancer-related pain is more compelling than that of chronic noncancer pain.

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