Ziconotide: a new option for refractory pain.

Ziconotide has been introduced as a new nonopioid treatment for chronic pain. Structurally, it is a peptide, the synthetic analog of the omega-conotoxin, derived from the marine snail, Conus magus. N-type voltage-sensitive calcium channels play a role in the transmission of nociceptive stimuli and also are involved in the release of neurotransmitters important in pain transmission. Ziconotide's therapeutic benefit derives from its potent and selective blockade of neuronal-type voltage-sensitive calcium channels. Blockade of the channels results in suppression of abnormal ectopic discharges from the injury site or the dorsal root ganglia, possibly resulting in decreased neuroplasticity, and decreased synaptic transmission that leads to the generation of chronic pain syndromes. The advantage of ziconotide is that tolerance does not occur, while disadvantages associated with ziconotide are the need for intrathecal administration and significant neurotoxicites associated with its use. When tested in clinical trials, ziconotide has been shown to have synergistic or additive value to the effect of morphine. Ziconotide, formerly known also as SNX- 111, represents a new class of agents, the N-type calcium channel blockers. These may represent another option for patients with refractory pain and refractory pain syndromes.