Intrathecal therapy with ziconotide: clinical experience and considerations on its use

Ziconotide is a synthetic peptide equivalent of an w-conotoxin, obtained from the marine snail Conus magus, which acts by blocking N-type calcium channels in the spinal cord, reducing the perception of pain. It is a newly marketed drug, exclusively for intrathecal use, indicated for severe chronic pain. Ziconotide came to the physicians' table with both doubts and promises; to determine its safety and efficacy, one of the largest and most well-designed randomized double-blind studies in the history of intrathecal therapy was undertaken, and this drug demonstrated efficacy in relieving chronic pain in patients coming from many years of different therapies and therapy failures. However, the pain relief came with some adverse effects, which are few compared with morphine's adverse effects but in some cases could undermine the course of therapy with this conotoxin. The experience described in this paper began in June 2007 and gave us the opportunity to analyze how the conotoxin works outside of the papers. We noted differences between the well-known activity of morphine on pain and mood, and the more focused action of ziconotide on pain. In addition, it is important to consider the lack of addiction, opioid-induced hyperalgesia and other systemic effects that are common with morphine. These are the reasons why the Polyanalgesic Consensus Conference of 2007 put ziconotide in the first line of intrathecal therapy management.