An evaluation of intrathecal ziconotide for the treatment of chronic pain.

Ziconotide, the synthetic form of cone snail peptide pi-conotoxin MVIIA, is a neurone-specific N-type calcium channel blocker with an analgesic and neuroprotective effect. Intrathecal ziconotide has been recommended for approval by the FDA for the management of chronic pain. Spinally administered ziconotide produces analgesia by blocking neurotransmitter release from primary nociceptive afferents and prevents the propagation of pain signals to the brain. It has an advantage over intrathecal morphine in that there is no development of tolerance after prolonged use. Systemic toxicity is considerably reduced by administration of smaller doses intrathecally and selective delivery to the site of action in the nervous system. Nevertheless, there are neurological adverse effects due to delay in clearance of ziconotide from the neural tissues. Overall, ziconotide has a favourable risk/benefit ratio with advantages over several currently available intrathecal therapies for pain.