Ziconotide

Prialt

Ziconotide is a synthetic 25-amino-acid peptide identical to ω-conotoxin MVIIA, a component of the venom of the marine cone snail Conus magus. It is one of the most striking examples of a natural venom peptide becoming a human medicine. Its target is the N-type voltage-gated calcium channel (Cav2.2), which sits on the presynaptic terminals of pain-transmitting nerves in the dorsal horn of the spinal cord. By blocking these channels, ziconotide prevents the release of pain neurotransmitters, interrupting pain signaling at the spinal level through a mechanism completely independent of the opioid system. Because the peptide cannot cross the blood-brain barrier and would be destroyed if taken by mouth, ziconotide is delivered by intrathecal infusion — directly into the cerebrospinal fluid via an implanted or external pump. Its approved use is the management of severe chronic pain in patients for whom intrathecal therapy is warranted and who are intolerant of, or unresponsive to, other treatments including systemic analgesics, adjunctive therapies, or intrathecal morphine. In other words, it is reserved for difficult, refractory pain, not first-line use. The defining challenge with ziconotide is its narrow therapeutic window and neuropsychiatric side-effect profile. It carries a boxed warning for severe psychiatric symptoms and neurological impairment, including cognitive changes, hallucinations, and mood disturbances, and it must be titrated slowly and monitored closely by a pain specialist experienced with intrathecal therapy. Crucially, it is not an opioid: it does not cause respiratory depression, tolerance, or physical dependence in the way opioids do, which is a meaningful advantage for a chronic-pain therapy. It was approved by the FDA in 2004 (Prialt). It is a specialist medicine used only within managed intrathecal pain programs.