Ziconotide: Definition

Detailed Explanation

Ziconotide (brand name Prialt) is a synthetic version of ω-conotoxin MVIIA, a 25-amino-acid peptide originally isolated from the venom of the marine cone snail Conus magus. It contains three disulfide bonds that create a rigid, compact structure essential for its pharmacological activity. Ziconotide was approved by the FDA in 2004 for the management of severe chronic pain in patients who are intolerant of or refractory to other therapies.

Ziconotide works by selectively blocking N-type voltage-gated calcium channels (Cav2.2) at presynaptic nerve terminals in the spinal cord dorsal horn. By blocking calcium influx, it prevents the release of neurotransmitters involved in pain signaling (substance P, glutamate, CGRP) from primary afferent nociceptors. This mechanism is entirely different from opioids — ziconotide does not bind opioid receptors and therefore does not cause respiratory depression, tolerance, or addiction, making it valuable for patients who cannot use opioid analgesics.

Because ziconotide cannot cross the blood–brain barrier, it must be delivered directly into the cerebrospinal fluid via intrathecal infusion using an implanted pump. This limits its use to severe cases, but it achieves potent, non-opioid analgesia. Side effects include dizziness, nausea, confusion, and, rarely, psychiatric symptoms. Ziconotide remains one of the most striking examples of venom-to-drug development and demonstrates the untapped pharmaceutical potential of the estimated 100,000+ peptides in cone snail venoms worldwide.

Key Facts

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