|Trade names||Prialt, others|
|Main uses||Severe chronic pain|
|Side effects||Dizziness, confusion, headache, nystagmus, sleepiness, psychosis|
|Intrathecal – directly into cerebrospinal fluid by a catheter|
|Elimination half-life||2.9 to 6.5 hours|
|Chemical and physical data|
|Molar mass||2639.14 g·mol−1|
|3D model (JSmol)|
Ziconotide, sold under the brand name Prialt among others, is a medication used for severe chronic pain. It is given by injection into the space around the spinal cord. Use is not recommended as of 2007 by NHS Scotland. The dose used is generally slowly increased over 3 weeks.
Common side effects include dizziness, confusion, headache, nystagmus, and sleepiness. Serious side effects may include psychosis or meningitis. It works by blocking neurons that sense pain by binding to N-type calcium channels. It is not an opioid.
Ziconotide was approved for medical use in the United States in 2004 and Europe in 2005. It was originally made from the venom of the snail Conus magus. Though is now a manufactured form of a ω-conotoxin peptide. In 2012 45 days of medication cost about 730 USD to 4,400 USD in the United States.
Due to the profound side effects or lack of efficacy when delivered through more common routes, such as orally or intravenously, ziconotide must be administered intrathecally (i.e. directly into the spinal fluid). As this is the most expensive and invasive method of drug delivery and involves additional risks of its own, ziconotide therapy is generally considered appropriate (as evidenced by the range of use approved by the FDA in the US) only for “management of severe chronic pain in patients for whom intrathecal (IT) therapy is warranted and who are intolerant of or refractory to other treatment, such as systemic analgesics, adjunctive therapies or IT morphine”. Research is ongoing to determine whether ziconotide can be formulated in a way that would allow it to be administered by less invasive means.
However, this must be weighed against the high level of pain management, both in terms of degree and length, and the apparent lack of tolerance and other signs of dependence even after extended treatment along with the need for alternatives to other therapies that have not worked for the patient. Ziconotide is also contraindicated for people with certain preexisting mental disorders (e.g. psychosis) due to evidence that they are more susceptible to certain severe side effects.
It is generally started at a dose of 2.4 micrograms per day with generally less than 10 micrograms per day required though doses may go as high as 21 micrograms per day.
The most common side effects are dizziness, nausea, confusion, nystagmus and headache. Others may include weakness, hypertonia, ataxia, abnormal vision, anorexia, somnolence, unsteadiness on feet, vertigo, urinary retention, pruritus, increased sweating, diarrhea, nausea, vomiting, asthenia, fever, rigors, sinusitis, muscle spasms, myalgia, insomnia, anxiety, amnesia, nystagmus, tremor, memory impairment and induced psychiatric disorders. Other side effects which are less frequent but still clinically significant include auditory and visual hallucinations, thoughts of suicide, acute kidney failure, atrial fibrillation, cardiovascular accident, sepsis, new or worsening depression, paranoia, disorientation, meningitis and seizures. Therefore, it is contraindicated in people with a history of psychosis, schizophrenia, clinical depression, and bipolar disorder. Recent incidents suggesting a link between intrathecal ziconotide treatment and increased risk of suicide have led to calls for strict and ongoing psychiatric monitoring of patients to avoid suicide occurring in vulnerable individuals. There is no known antidote.
Mechanism of action
Ziconotide is a hydrophilic molecule that is freely soluble in water and is practically insoluble in methyl t-butyl ether. Ziconotide acts as a selective N-type voltage-gated calcium channel blocker. This action inhibits the release of pro-nociceptive neurochemicals like glutamate, calcitonin gene-related peptide (CGRP), and substance P in the brain and spinal cord, resulting in pain relief.
Ziconotide is derived from the toxin of the cone snail species Conus magus. Scientists have been intrigued by the effects of the thousands of chemicals in marine snail toxins since the initial investigations in the late 1960s by Baldomero Olivera. Olivera, now a professor of biology in the University of Utah, was inspired by accounts of the deadly effects of these toxins from his childhood in the Philippines. Ziconotide was discovered in the early 1980s by University of Utah research scientist Michael McIntosh, when he was barely out of high school and working with Baldomero Olivera.
Ziconotide was developed into an artificially manufactured drug by Elan Corporation. It was approved for sale under the name Prialt by the U.S. Food and Drug Administration on December 28, 2004, and by the European Commission on February 22, 2005. Azur Pharma acquired worldwide rights (except Europe) to Prialt in 2010.
Society and culture
The drug was patented by Neurex Corp., a U.S. company purchased in 1998 by Élan Corporation, plc of Ireland. U.S. patents assigned to Elan include 5,859,186, 5,795,864 5,770,690, 5,587,454, and 5,587,454.
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