Phase II, Open-Label, Multicenter Study of Combined Intrathecal Morphine and Ziconotide: Addition of Ziconotide in Patients Receiving Intrathecal Morphine for Severe Chronic Pain

A comprehensive review on ziconotide

Managing severe chronic pain is a challenging task, given the limited effectiveness of available pharmacological and non-pharmacological treatments. This issue continues to be a significant public health concern, requiring a substantial therapeutic response. Ziconotide, a synthetic peptide initially isolated from Conus magus in 1982 and approved by the US Food and Drug Administration and the European Medicines Agency in 2004, is the first-line intrathecal method for individuals experiencing severe chronic pain refractory to other therapeutic measures. Ziconotide produces powerful analgesia by blocking N-type calcium channels in the spinal cord, which inhibits the release of pain-relevant neurotransmitters from the central terminals of primary afferent neurons. However, despite possessing many favorable qualities, including the absence of tolerance development, respiratory depression, and withdrawal symptoms (largely due to the absence of a G-protein mediation mechanism), ziconotide's application is limited due to factors such as intrathecal administration and a narrow therapeutic window resulting from significant dose-related undesired effects of the central nervous system. This review aims to provide a comprehensive and clinically relevant summary of the literatures concerning the pharmacokinetics and metabolism of intrathecal ziconotide. It will also describe strategies intended to enhance clinical efficacy while reducing the incidence of side effects. Additionally, the review will explore the current efforts to refine the structure of ziconotide for better clinical outcomes. Lastly, it will prospect potential developments in the new class of selective N-type voltage-sensitive calcium-channel blockers.

The American Society of Pain and Neuroscience (ASPN) Evidence-Based Clinical Guideline of Interventional Treatments for Low Back Pain

Introduction

Painful lumbar spinal disorders represent a leading cause of disability in the US and worldwide. Interventional treatments for lumbar disorders are an effective treatment for the pain and disability from low back pain. Although many established and emerging interventional procedures are currently available, there exists a need for a defined guideline for their appropriateness, effectiveness, and safety.

Objective

The ASPN Back Guideline was developed to provide clinicians the most comprehensive review of interventional treatments for lower back disorders. Clinicians should utilize the ASPN Back Guideline to evaluate the quality of the literature, safety, and efficacy of interventional treatments for lower back disorders.

Methods

The American Society of Pain and Neuroscience (ASPN) identified an educational need for a comprehensive clinical guideline to provide evidence-based recommendations. Experts from the fields of Anesthesiology, Physiatry, Neurology, Neurosurgery, Radiology, and Pain Psychology developed the ASPN Back Guideline. The world literature in English was searched using Medline, EMBASE, Cochrane CENTRAL, BioMed Central, Web of Science, Google Scholar, PubMed, Current Contents Connect, Scopus, and meeting abstracts to identify and compile the evidence (per section) for back-related pain. Search words were selected based upon the section represented. Identified peer-reviewed literature was critiqued using United States Preventive Services Task Force (USPSTF) criteria and consensus points are presented.

Results

After a comprehensive review and analysis of the available evidence, the ASPN Back Guideline group was able to rate the literature and provide therapy grades to each of the most commonly available interventional treatments for low back pain.

Conclusion

The ASPN Back Guideline represents the first comprehensive analysis and grading of the existing and emerging interventional treatments available for low back pain. This will be a living document which will be periodically updated to the current standard of care based on the available evidence within peer-reviewed literature.

Analgesic effect of recombinant GABAergic precursors releasing MVIIA in a model of peripheral nerve injury in rats

Development of chronic pain has been attributed to dysfunctional GABA signaling in the spinal cord. Direct pharmacological interventions on GABA signaling are usually not very efficient and often accompanied by side effects due to the widespread distribution of GABA receptors in CNS. Transplantation of GABAergic neuronal cells may restore the inhibitory potential in the spinal cord. Grafted cells may also release additional analgesic peptides by means of genetic engineering to further enhance the benefits of this approach. Conopeptides are ideal candidates for recombinant expression using cell-based strategies. The omega-conopeptide MVIIA is in clinical use for severe pain marketed as FDA approved Prialt in the form of intrathecal injections. The goal of this study was to develop transplantable recombinant GABAergic cells releasing conopeptide MVIIA and to evaluate the analgesic effect of the grafts in a model of peripheral nerve injury-induced pain. We have engineered and characterized the GABAergic progenitors expressing MVIIA. Recombinant and nonrecombinant cells were intraspinally injected into animals after the nerve injury. Animals were tested weekly up to 12 weeks for the presence of hypersensitivity, followed by histochemical and biochemical analysis of the tissue. We observed beneficial effects of the grafted cells in reducing hypersensitivity in all grafted animals, especially potent in the recombinant group. The level of pain-related cytokines was reduced in the grafted animals and correlation between these pain markers and actual behavior was indicated. This study demonstrated the feasibility of recombinant cell transplantation in the management of chronic pain.

Effects of Ultramicronized N-Palmitoylethanolamine Supplementation on Tramadol and Oxycodone Analgesia and Tolerance Prevention

Chronic pain management requires increasing doses of opioids, the milestone of painkillers, which may result in the onset of tolerance with exacerbated side effects. Maintaining stable analgesia with low doses of opioids is thus imperative. N-palmitoylethanolamine (PEA) is an endogenous lipid compound endowed with pain-relieving as well as anti-inflammatory properties. The ultramicronized formulation of PEA was recently demonstrated to be able to modulate morphine’s effects, delaying tolerance and improving efficacy. To evaluate the possible application to other opioids, in this study, we analysed the capacity of ultramicronized PEA to regulate analgesia and tolerance induced by oxycodone and tramadol. Pre-emptive and continuative treatment with ultramicronized PEA (30 mg kg⁻¹, daily, per os) delayed the onset of opioid tolerance and enhanced opioid analgesia when it was acutely administered in association with tramadol (20 mg kg⁻¹, daily, subcutaneously) or oxycodone (0.5 mg kg⁻¹, daily, subcutaneously). Moreover, PEA exerted antinociceptive effects on tolerant rats, suggesting the use of PEA together with opioids for stable, long-lasting analgesia. To that purpose, the oxycodone dose needed to be increased from 0.3 mg kg⁻¹ (day 1) up to 1 mg kg⁻¹ (day 31) in the oxycodone + vehicle group; the tramadol dose was progressively enhanced from 15 mg kg⁻¹ to 50 mg kg⁻¹ in 31 days in the tramadol + vehicle group. Acute oral co-treatment with PEA (120 mg kg⁻¹) achieved the same analgesia without increasing the dose of both opioids. The behavioural effects of PEA on opioid chronic treatment paralleled a decrease in astrocyte activation in the dorsal horn of the spinal cord (a marker of the development of opioid tolerance) and with a modulation of mRNA expression of IL-6 and serpin-A3. In conclusion, pre- and co-administration of ultramicronized PEA delayed the development of tramadol tolerance, potentiating either oxycodone or tramadol analgesia and allowing a long-lasting analgesic effect with a low opioid dose regimen. The use of PEA is suggested for clinical purposes to support the opioid-based management of persistent pain.

Physicochemical Stability Study of the Morphine-Ropivacaine-Ziconotide Association in Implantable Pumps for Intrathecal Administration

PURPOSE

This study aimed to investigate the physicochemical stability of morphine-ropivacaine-ziconotide mixtures used in intrathecal analgesia.

MATERIALS AND METHODS

Eight mixtures were studied to assess their stability profiles according to the initial drug concentrations used. The solutions obtained were put in implantable pumps and stored at 37 °C over a period of 60 days. Assays were performed using ultra high-pressure liquid chromatography. Turbidity and pH were also measured throughout the study.

RESULTS

Results confirmed excellent physicochemical stability for morphine and ropivacaine. Concerning ziconotide, three of the eight mixtures did not show any sign of chemical instability: average concentrations remained constant throughout the 60 days. A decrease of the concentration was observed for the five other mixtures. Moreover, the appearance of a degradation product linked to oxidation confirmed the ziconotide degradation.

CONCLUSIONS

All these results are in favor of a physicochemical stable preparation for three of the mixture profiles when stored in implantable pumps at 37 °C up to 60 days. For the five others, the efficacy should decrease over time owing to the degradation of ziconotide. The decrease in kinetics of the ziconotide concentration depends on the mixing profile. One possibility is to adapt the filling intervals according to the profile of the mixture. Finally, the results show the period of stability ensuring maximum analgesic efficacy for the eight mixture profiles studied.

Analgesic effects of Phα1β toxin: a review of mechanisms of action involving pain pathways

Phα1β is a neurotoxin purified from spider venom that acts as a high-voltage-activated (HVA) calcium channel blocker. This spider peptide has shown a high selectivity for N-type HVA calcium channels (NVACC) and an analgesic effect in several animal models of pain. Its activity was associated with a reduction in calcium transients, glutamate release, and reactive oxygen species production from the spinal cord tissue and dorsal ganglia root (DRG) in rats and mice. It has been reported that intrathecal (i.t.) administration of Phα1β to treat chronic pain reverted opioid tolerance with a safer profile than ω-conotoxin MVIIA, a highly selective NVACC blocker. Following a recent development of recombinant Phα1β (CTK 01512-2), a new molecular target, TRPA1, the structural arrangement of disulphide bridges, and an effect on glial plasticity have been identified. CTK 01512-2 reproduced the antinociceptive effects of the native toxin not only after the intrathecal but also after the intravenous administration. Herein, we review the Phα1β antinociceptive activity in the most relevant pain models and its mechanisms of action, highlighting the impact of CTK 01512-2 synthesis and its potential for multimodal analgesia.

Opioid Analgesia and Opioid-Induced Adverse Effects: A Review

Opioids are widely used as therapeutic agents against moderate to severe acute and chronic pain. Still, these classes of analgesic drugs have many potential limitations as they induce analgesic tolerance, addiction and numerous behavioural adverse effects that often result in patient non-compliance. As opium and opioids have been traditionally used as painkillers, the exact mechanisms of their adverse reactions over repeated use are multifactorial and not fully understood. Older adults suffer from cancer and non-cancer chronic pain more than younger adults, due to the physiological changes related to ageing and their reduced metabolic capabilities and thus show an increased number of adverse reactions to opioid drugs. All clinically used opioids are μ-opioid receptor agonists, and the major adverse effects are directly or potentially connected to this receptor. Multifunctional opioid ligands or peripherally restricted opioids may elicit fewer adverse effects, as shown in preclinical studies, but these results need reproducibility from further extensive clinical trials. The current review aims to overview various mechanisms involved in the adverse effects induced by opioids, to provide a better understanding of the underlying pathophysiology and, ultimately, to help develop an effective therapeutic strategy to better manage pain.

Comparative Analysis of Dorsal Root, Nodose and Sympathetic Ganglia for the Development of New Analgesics

Interoceptive and exteroceptive signals, and the corresponding coordinated control of internal organs and sensory functions, including pain, are received and orchestrated by multiple neurons within the peripheral, central and autonomic nervous systems. A central aim of the present report is to obtain a molecularly informed basis for analgesic drug development aimed at peripheral rather than central targets. We compare three key peripheral ganglia: nodose, sympathetic (superior cervical), and dorsal root ganglia in the rat, and focus on their molecular composition using next-gen RNA-Seq, as well as their neuroanatomy using immunocytochemistry and in situ hybridization. We obtained quantitative and anatomical assessments of transmitters, receptors, enzymes and signaling pathways mediating ganglion-specific functions. Distinct ganglionic patterns of expression were observed spanning ion channels, neurotransmitters, neuropeptides, G-protein coupled receptors (GPCRs), transporters, and biosynthetic enzymes. The relationship between ganglionic transcript levels and the corresponding protein was examined using immunohistochemistry for select, highly expressed, ganglion-specific genes. Transcriptomic analyses of spinal dorsal horn and intermediolateral cell column (IML), which form the termination of primary afferent neurons and the origin of preganglionic innervation to the SCG, respectively, disclosed pre- and post-ganglionic molecular-level circuits. These multimodal investigations provide insight into autonomic regulation, nodose transcripts related to pain and satiety, and DRG-spinal cord and IML-SCG communication. Multiple neurobiological and pharmacological contexts can be addressed, such as discriminating drug targets and predicting potential side effects, in analgesic drug development efforts directed at the peripheral nervous system.

Ziconotide-induced psychosis: A case report and literature review

Ziconotide is an intrathecally administered medication indicated for the treatment of severe chronic pain in patients who are intolerant of or refractory to other treatment options. A black box warning is included in the packaging and states ziconotide is contraindicated in patients with a preexisting history of psychosis. Patients taking ziconotide should be monitored for evidence of cognitive impairment, hallucinations, or changes in mood, and ziconotide should be discontinued if neurological or psychiatric signs and symptoms appear. We present a case of a 49-year-old white male with no previous neuropsychiatric history who received ziconotide for several years before he developed command auditory hallucinations within 24 hours of a dose increase. Upon admission to the emergency room, the patient's pain management physician was contacted and the ziconotide dose was decreased and eventually discontinued. Because of a continuation of symptoms, the patient was transferred from the emergency room to an acute care psychiatric hospital where he was started on risperidone 1 mg orally at bedtime. At discharge, the patient was noted to be in good behavioral control without any hallucinations. The patient was encouraged to follow up with his pain management physician to determine if ziconotide should be reconsidered.

Ziconotide Monotherapy: A Systematic Review of Randomised Controlled Trials

INTRODUCTION

Chronic neuropathic pain is difficult to treat and is often refractory to most modalities of treatment. Ziconotide is a novel, potent, non-opioid, calcium channel blocking agent which has been shown in clinical trials to be effective in treating chronic neuropathic pain.

METHODS

EMBASE, MEDLINE, CINAHL Plus and Web of Science electronic databases were searched for English language studies. Reference sections of articles were examined for further papers and the manufacturer of ziconotide was contacted for further unpublished data. Three randomised controlled trials in ziconotide monotherapy were included and subjected to a random effects meta-analysis.

RESULTS

All three studies used the similar main outcome measure (visual analogue scale of pain intensity; VASPI) and were therefore comparable. A Jadad score was performed for each paper. Frequent serious adverse events (SAEs) were observed which resulted in two of the studies revising the protocol. The metaanalysis revealed a pooled odds ratio (responders on ziconotide vs. placebo) of 2.77 (95% CI, 1.37 to 5.59).

DISCUSSION

The results suggest that ziconotide is beneficial for pain reduction in chronic neuropathic pain. However, there remain some methodological issues that may call into question the validity of the results. It is evident that more work needs to be conducted to further validate the efficacy of ziconotide and to discover new areas of use.

Clinical Uses of Intrathecal Therapy and Its Placement in the Pain Care Algorithm

Intrathecal drug delivery is an effective treatment option for patients with severe chronic pain who have not obtained adequate analgesia from more conservative therapies (eg, physical therapy, systemic opioids, nonsteroidal anti-inflammatory drugs, antidepressants, and anticonvulsants). This review focuses on, but is not limited to, the 2 agents currently approved by the U.S. Food and Drug Administration for intrathecal analgesia: preservative-free morphine and ziconotide (a nonopioid, selective N-type calcium channel blocker). We describe the appropriate use of intrathecal therapy in the management of severe chronic pain, based on current best practices. Topics addressed here include patient selection, trialing, dosing and titration, adverse event profiles, long-term management, intrathecal therapy for cancer-related pain, and the placement of intrathecal therapy in the pain care algorithm. In appropriately selected patients with chronic pain, intrathecal therapy can provide substantial pain relief with improved functioning and quality of life. Successful long-term management requires ongoing patient monitoring for changes in efficacy and the occurrence of adverse events, with subsequent changes in intrathecal dosing and titration, the addition of adjuvant intrathecal agents, and the use of concomitant oral medications to address side effects, as needed. Based on an infrequent but clinically concerning risk of overdose, granuloma, and other opioid-induced complications, nonopioid therapy with ziconotide may be preferred as a first-line intrathecal therapy in patients without a history of psychosis or allergy.

Interventional options for the management of refractory cancer pain--what is the evidence?

PURPOSE

Pain is the most common symptom in cancer patients. Standard pain treatment according to the WHO three-step analgesic ladder provides effective pain management in approximately 70-90% of cancer patients. Refractory pain is defined as not responding to "standard" treatments. Interventional analgesic techniques can be used in an attempt to control refractory pain in patients in whom conventional analgesic strategies fail to provide effective pain relief or are intolerable due to severe adverse effects. This systematic review aims to provide the latest evidence on interventional refractory pain management in cancer patients.

METHODS

Systematic literature search in Cochrane, EMBASE and PubMed including reviews and randomised controlled trials (RCTs) and non-randomised controlled trials in the absence of reviews.

RESULTS

Neuraxial analgesia may play a role in refractory cancer pain management. Paravertebral blocks decrease the incidence of persistent post-surgical pain after breast cancer. Coeliac plexus blocks improve pain scores in refractory pancreatic cancer pain for up to 4 weeks after the intervention with fewer burdensome side effects as compared to opioids. Cordotomy has mainly been studied in mesothelioma, and the case series suggest possible benefit for pain at the expense of a relatively high risk of side effects.

CONCLUSIONS

Overall, very few RCTs have been conducted on interventional pain techniques. In reality, it is very difficult to undertake large controlled trials for a number of reasons. Therefore, today's best evidence for practice may be from large case series of comparable patients with careful response and toxicity evaluation and follow-up.

Intrathecal Ziconotide and Morphine for Pain Relief: A Case Series of Eight Patients with Refractory Cancer Pain, Including Five Cases of Neuropathic Pain

Introduction

Studies have shown that, at low doses and with careful titration, combination therapy with intrathecal ziconotide and morphine results in rapid control of opioid-refractory cancer pain. However, there is a lack of published data regarding the efficacy and safety of intrathecal ziconotide specifically for the treatment of neuropathic cancer pain.

Case series

Case reports of ziconotide intrathecal infusion in eight patients (age 45–71 years; 75% male) with chronic, uncontrolled cancer pain during therapy with intrathecal morphine plus bupivacaine were reviewed. Neuropathic pain was confirmed in five patients. Treatment was initiated with adjunctive ziconotide when pain ≥5 on a visual analog scale persisted in spite of 3 successive 20% dose increases of intrathecal morphine. Ziconotide was initiated at 0.5–1.0 µg/day, with mean increases of 0.5 µg every 4–7 days if required (maximum dose 10 µg/day; mean dose 4.9 µg/day). Pain intensity was reduced in all patients after 3–5 days. Of the eight patients, three died for reasons unrelated to ziconotide, three discontinued treatment due to adverse effects (predominantly psychoneurological disorders), and one patient is still receiving treatment. One patient discontinued ziconotide due to confusion and delirium. Due to continued lack of pain control with intrathecal morphine, intrathecal fentanyl was initiated; however, effective pain relief was not achieved with 1500 µg/day. Ziconotide was restarted and the patient then achieved pain control.

Conclusion

On the basis of our clinical experience, we recommend adding ziconotide to intrathecal opioid-based therapy in cancer patients with neuropathic pain inadequately controlled by intrathecal morphine alone.

Funding

Eisai, Spain.

Electronic supplementary material

The online version of this article (doi:10.1007/s40120-015-0035-z) contains supplementary material, which is available to authorized users.

Ziconotide Combination Intrathecal Therapy for Noncancer Pain Is Limited Secondary to Delayed Adverse Effects: A Case Series With a 24-Month Follow-Up

OBJECTIVES

The efficacy and safety of ziconotide as a single agent has been evaluated in few short-term clinical trials and open-label studies. Ziconotide use is challenging given its adverse effect (AE) profile. The objective of this study is to describe the long-term efficacy and AEs of ziconotide used as an adjunct to other intrathecal (IT) agents in chronic noncancer pain patients.

MATERIALS AND METHODS

A case series of chronic noncancer pain patients who had suboptimal pain control from IT therapy. Ziconotide was introduced in the IT infusion mixture after a successful ziconotide trial. Pain scores, IT doses, as well as AEs were recorded and analyzed from trial to initial ziconotide infusion and up to 24 months.

RESULTS

Fifteen patients underwent ziconotide trials. Four subjects failed the trial, and 11 proceeded to continuous ziconotide treatment. Seven out of 11 patients experienced AEs resulting in ziconotide discontinuation. Two of the seven subjects who required discontinuation of ziconotide had improved pain. Four subjects were able to continue IT ziconotide through 24 months.

CONCLUSIONS

A high incidence of AEs limits the usefulness of IT ziconotide as adjunct therapy. Our results are limited by the size of our patient population; however, they represent a long follow-up period, which is limited in most current publications on this IT peptide. While ziconotide is a needed IT agent, more studies are necessary to better understand the factors that would improve the treatment to trial ratio as well as the long-term efficacy of IT ziconotide treatment.

Pharmacological characterization of conotoxin lt14a as a potent non-addictive analgesic

Conotoxin lt14a is a small peptide consisting of 13 amino acids. It was originally identified from the cDNA of Conus litteratus in the South China Sea. Previous reports showed lt14a exhibited antinociceptive activity using a hot plate-induced pain mouse model and acted as an antagonist of neuronal nicotinic acetylcholine receptors. We confirmed that conotoxin lt14a administration resulted in antinociception activity using a mouse inflammatory pain model and a rat model of mechanically-induced pain. The mRNA expression of c-fos and NOS in the spinal cord of rats was suppressed by lt14a. Labeling of lt14a with an Alexa Fluor 488 ester showed that lt14a was bound to the surface of PC12 cells and that this binding was inhibited by pre-application of the nicotinic acetylcholine receptor (nAChR) antagonist tubocurarine chloride (TUB) and the nAChR blocker hexamethonium bromide (HB). These data confirm previous reports that showed lt14a binds to the surface of PC12 cells via nAChRs with patch clamp whole-cell recordings. Additional results showed that lt14a suppressed extracellular signal-regulated kinase (ERK1/2) phosphorylation in PC12 cells activated by Ach. Our results showed that lt14a did not induce drug dependence but rather suppressed morphine withdrawal symptoms. Our work suggests that lt14a is a novel antinociceptive agent that targets the nAChR receptor without inducing drug dependence.

The use of combined spinal-epidural technique to compare intrathecal ziconotide and epidural opioids for trialing intrathecal drug delivery

SUMMARY Choosing the initial medications for intrathecal delivery is often confusing and not standardized. We describe a novel way for using a combined spinal-epidural technique to compare two first-line medications for intrathecal delivery; ziconotide and morphine (or hydromorphone). Five patients with intractable chronic or cancer pain were elected to have an intrathecal drug delivery system implanted for pain management. Each patient was given a 3-day inpatient trial with the combined spinal-epidural technique. The Visual Analog Scale, Numerical Rating Scale, short-term McGill questionnaire and opioid consumption were monitored daily. The results were used to develop a paradigm to describe how ziconotide can be used in practice.

Neuropathic cancer pain: What we are dealing with? How to manage it?

Cancer pain is a serious health problem, and imposes a great burden on the lives of patients and their families. Pain can be associated with delay in treatment, denial of treatment, or failure of treatment. If the pain is not treated properly it may impair the quality of life. Neuropathic cancer pain (NCP) is one of the most complex phenomena among cancer pain syndromes. NCP may result from direct damage to nerves due to acute diagnostic/therapeutic interventions. Chronic NCP is the result of treatment complications or malignancy itself. Although the reason for pain is different in NCP and noncancer neuropathic pain, the pathophysiologic mechanisms are similar. Data regarding neuropathic pain are primarily obtained from neuropathic pain studies. Evidence pertaining to NCP is limited. NCP due to chemotherapeutic toxicity is a major problem for physicians. In the past two decades, there have been efforts to standardize NCP treatment in order to provide better medical service. Opioids are the mainstay of cancer pain treatment; however, a new group of therapeutics called coanalgesic drugs has been introduced to pain treatment. These coanalgesics include gabapentinoids (gabapentin, pregabalin), antidepressants (tricyclic antidepressants, duloxetine, and venlafaxine), corticosteroids, bisphosphonates, N-methyl-D-aspartate antagonists, and cannabinoids. Pain can be encountered throughout every step of cancer treatment, and thus all practicing oncologists must be capable of assessing pain, know the possible underlying pathophysiology, and manage it appropriately. The purpose of this review is to discuss neuropathic pain and NCP in detail, the relevance of this topic, clinical features, possible pathology, and treatments of NCP.

Intrathecal ziconotide: a review of its use in patients with chronic pain refractory to other systemic or intrathecal analgesics

Ziconotide (Prialt(®)) is a synthetic conopeptide analgesic that acts by selectively antagonizing N-type voltage-gated calcium channels. Intrathecal ziconotide is the only non-opioid intrathecal analgesic that is FDA-approved for use in patients with treatment-refractory, chronic pain. The efficacy of intrathecal ziconotide was demonstrated in randomized, double-blind, placebo-controlled trials in patients with treatment-refractory noncancer-related pain or cancer- or AIDS-related pain. Across trials, ziconotide recipients had significantly greater reductions in pain intensity during ziconotide treatment than those receiving placebo (primary endpoint). At the end of the titration period, approximately one-sixth to one-third of patients with noncancer chronic pain and one-half with cancer- or AIDS-related pain who received ziconotide reached a pain response threshold (≥30 % reduction in the pain intensity score). In ziconotide responders, analgesic effects were enduring, with some patients continuing treatment over extended periods. Across trials, the chief tolerability concerns in ziconotide recipients during the titration phase and during extended treatment were related to CNS adverse events. These were mostly of mild to moderate intensity, although serious adverse events were commonly attributed to ziconotide treatment, especially in trials with rapid ziconotide titration and that permitted higher dosages. In general, clinically important non-CNS adverse events were infrequent, and during the ziconotide titration phase, relatively few patients discontinued treatment because of adverse events. Ongoing research will assess various strategies for selecting patients for ziconotide treatment and for enhancing its efficacy and tolerability. At the present time, intrathecal ziconotide provides a treatment option for patients with severe, unremitting pain who have failed to respond to other intensive analgesic regimens.

Polyanalgesic Consensus Conference 2012: recommendations for the management of pain by intrathecal (intraspinal) drug delivery: report of an interdisciplinary expert panel

INTRODUCTION

The use of intrathecal (IT) infusion of analgesic medications to treat patients with chronic refractory pain has increased since its inception in the 1980s, and the need for clinical research in IT therapy is ongoing. The Polyanalgesic Consensus Conference (PACC) panel of experts convened in 2000, 2003, and 2007 to make recommendations on the rational use of IT analgesics based on preclinical and clinical literature and clinical experiences.

METHODS

The PACC panel convened again in 2011 to update the standard of care for IT therapies to reflect current knowledge gleaned from literature and clinical experience. A thorough literature search was performed, and information from this search was provided to panel members. Analysis of published literature was coupled with the clinical experience of panel members to form recommendations regarding the use of IT analgesics to treat chronic pain.

RESULTS

After a review of literature published from 2007 to 2011 and discussions of clinical experience, the panel created updated algorithms for the rational use of IT medications for the treatment of neuropathic pain and nociceptive pain.

CONCLUSIONS

The advent of new algorithmic tracks for neuropathic and nociceptive pain is an important step in improving patient care. The panel encourages continued research and development, including the development of new drugs, devices, and safety recommendations to improve the care of patients with chronic pain.

Safety and efficacy of intrathecal drug delivery for pain

SUMMARY The practice of delivering analgesic drugs into the intrathecal space has evolved over the past several decades from a ‘last-ditch’ therapy for intractable pain in patients with terminal cancer to a more widely applied strategy for treating patients with chronic nonmalignant pain as well. This review discusses the available safety and efficacy data of intrathecal drug delivery with a focus on device- and user-related safety issues.

Antinociceptive effect of Brazilian armed spider venom toxin Tx3-3 in animal models of neuropathic pain

Venoms peptides have produced exceptional sources for drug development to treat pain. In this study we examined the antinociceptive and side effects of Tx3-3, a peptide toxin isolated from Phoneutria nigriventer venom, which inhibits high-voltage-dependent calcium channels (VDCC), preferentially P/Q and R-type VDCC. We tested the effects of Tx3-3 in animal models of nociceptive (tail-flick test), neuropathic (partial sciatic nerve ligation and streptozotocin-induced diabetic neuropathy), and inflammatory (intraplantar complete Freund's adjuvant) pain. In the tail-flick test, both intrathecal (i.t.) and intracerebroventricular (i.c.v.) injection of Tx3-3 in mice caused a short-lasting effect (ED(50) and 95% confidence intervals of 8.8 [4.1-18.8] and 3.7 [1.6-8.4] pmol/site for i.t. and i.c.v. injection, respectively), without impairing motor functions, at least at doses 10-30 times higher than the effective dose. By comparison, ω-conotoxin MVIIC, a P/Q and N-type VDCC blocker derived from Conus magus venom, caused significant motor impairment at doses close to efficacious dose in tail flick test. Tx3-3 showed a long-lasting antinociceptive effect in neuropathic pain models. Intrathecal injection of Tx3-3 (30 pmol/site) decreased both mechanical allodynia produced by sciatic nerve injury in mice and streptozotocin-induced allodynia in mice and rats. On the other hand, i.t. injection of Tx3-3 did not alter inflammatory pain. Taken together, our data show that Tx3-3 shows prevalent antinociceptive effects in the neuropathic pain models and does not cause adverse motor effects at antinociceptive efficacious doses, suggesting that this peptide toxin holds promise as a novel therapeutic agent for the control of neuropathic pain. The Brazilian armed spider Tx3-3, a new P/Q and R-type calcium channel blocker, effectively alleviates allodynia in animal neuropathic pain models.

Current developments in intraspinal agents for cancer and noncancer pain

Since the late 1980s, intrathecal (IT) analgesic therapy has improved, and implantable IT drug delivery devices have become increasingly sophisticated. Physicians and patients now have myriad more options for agents and their combination, as well as for refining their delivery. As recently as 2007, The Polyanalgesic Consensus Conference of expert panelists updated its algorithm for drug selection in IT polyanalgesia. We review this algorithm and the emerging therapy included. This article provides an update on newly approved as well as emerging IT agents and the advances in technology for their delivery.

Ziconotide for treatment of severe chronic pain

Pharmacological management of severe chronic pain is difficult to achieve with currently available analgesic drugs, and remains a large unmet therapeutic need. The synthetic peptide ziconotide has been approved by the US Food and Drug Administration and the European Medicines Agency for intrathecal treatment of patients with severe chronic pain that is refractory to other treatment modalities. Ziconotide is the first member in the new drug class of selective N-type voltage-sensitive calcium-channel blockers. The ziconotide-induced blockade of N-type calcium channels in the spinal cord inhibits release of pain-relevant neurotransmitters from central terminals of primary afferent neurons. By this mechanism, ziconotide can effectively reduce pain. However, ziconotide has a narrow therapeutic window because of substantial CNS side-effects, and thus treatment with ziconotide is appropriate for only a small subset of patients with severe chronic pain. We provide an overview of the benefits and limitations of intrathecal ziconotide treatment and review potential future developments in this new drug class.

Intrathecal therapy: what has changed with the introduction of ziconotide

Administering drugs into the intrathecal space is becoming more popular in the treatment of patients with intractable pain or intolerable side effects of systemic analgesic treatments. Although morphine and ziconotide are the only intrathecal analgesics currently approved by regulatory authorities in the U.S. (Food and Drug Administration) and Europe (national-level approval by individual countries for morphine and European Agency for the Evaluation of Medicinal Products approval for ziconotide), a wide variety of opioid and non-opioid drugs are being used in this way. There is no official guidance concerning the selection of these drugs or their use in combinations and a paucity of efficacy and safety data from randomized controlled trials. The polyanalgesic initiative aims to summarize the current knowledge and to facilitate rational choices of intrathecal drug and drug combinations for the management of chronic pain. The most recent polyanalgesic consensus recommendations were published in 2007. In this review, we shall examine these recommendations, which are tailored toward those practicing intrathecal analgesia in the U.S., and discuss how they should be implemented in Europe, where the healthcare systems and regulations of the medical authorities are different.

Intrathecal ziconotide for neuropathic pain: a review

Neuropathic pain is a considerable burden that affects activities of daily living. The management of neuropathic pain can be challenging because of multiple etiologies and complex manifestations. Ziconotide is a nonopioid intrathecal (IT) analgesic option for patients with neuropathic pain refractory to conventional treatments. The objective of this article is to review the published literature on ziconotide for the treatment of neuropathic pain. Relevant publications were identified through searches of all years of 6 databases, which included PubMed, EMBASE, and CINAHL. Search terms used were ziconotide, SNX-111, MVIIA, Prialt, and neuropathic pain. Publications were included if ziconotide was intrathecally administered (either alone or in combination with other IT agents) to treat neuropathic pain of any etiology and if pain assessment was an outcome measure. Data extracted included study design, IT drug doses, pain outcome measures, and adverse events (AEs). Twenty-eight articles met the inclusion criteria: 5 were preclinical studies and 23 were clinical studies. In the preclinical studies, ziconotide demonstrated antiallodynic effects on neuropathic pain. Data from double-blind, placebo-controlled (DBPC) trials indicated that patients with neuropathic pain reported a mean percent improvement in pain score with ziconotide monotherapy that ranged from 15.7% to 31.6%. A low starting dose and slow titration of ziconotide resulted in an improved safety profile in the aforementioned trials. Common AEs associated with ziconotide include nausea and/or vomiting, dizziness, confusion, urinary retention, and somnolence. Evidence from DBPC trials, open-label studies, case series, and case studies suggests that ziconotide, as either monotherapy or in combination with other IT drugs, is a potential therapeutic option for patients with refractory neuropathic pain. Additional studies are needed to establish the long-term efficacy and safety of ziconotide for neuropathic pain.

Safety and efficacy of intrathecal ziconotide in the management of severe chronic pain

Ziconotide is a conopeptide intrathecal (IT) analgesic which is approved by the US Food and Drug Administration (FDA) for the management of severe chronic pain. It is a synthetic equivalent of a naturally occurring conopeptide found in the venom of the fish-eating marine cone snail and provides analgesia via binding to N-type voltage-sensitive calcium channels in the spinal cord. As ziconotide is a peptide, it is expected to be completely degraded by endopeptidases and exopeptidases (Phase I hydrolytic enzymes) widely located throughout the body, and not by other Phase I biotransformation processes (including the cytochrome P450 system) or by Phase II conjugation reactions. Thus, IT administration, low plasma ziconotide concentrations, and metabolism by ubiquitous peptidases make metabolic interactions of other drugs with ziconotide unlikely. Side effects of ziconotide which tend to occur more commonly at higher doses may include: nausea, vomiting, confusion, postural hypotension, abnormal gait, urinary retention, nystagmus/amblyopia, drowsiness/somnolence (reduced level of consciousness), dizziness or lightheadedness, weakness, visual problems (eg, double vision), elevation of serum creatine kinase, or vestibular side effects. Initially, when ziconotide was first administered to human subjects, titration schedules were overly aggressive and led to an abundance of adverse effects. Subsequently, clinicians have gained appreciation for ziconotide’s relatively narrow therapeutic window. With appropriate usage multiple studies have shown ziconotide to be a safe and effective intrathecal analgesic alone or in combination with other intrathecal analgesics.

Antinociceptive effects of the marine snail peptides conantokin-G and conotoxin MVIIA alone and in combination in rat models of pain

There are a number of neurologically active ion channel blocking peptides derived from cone snail venom, such as conantokin-G and omega-conotoxin MVIIA. Conantokin-G inhibits NMDA receptors containing the NR2B subunit whereas omega-conotoxin MVIIA blocks N-type Ca(2+) channels. Separately, these peptides induce antinociceptive effects in pre-clinical pain models following intrathecal injection. In the current study, the efficacies of these peptides were determined separately and in combination by intrathecal injection into rats with a spinal nerve ligation, in rats with a spinal cord compression injury and in the formalin test. Separately, both conantokin-G and omega-conotoxin MVIIA dose-dependently attenuated nociceptive responses in all of these models. However, at high antinociceptive doses for both formalin and nerve injury models, omega-conotoxin MVIIA evoked untoward side effects. Using isobolographic analysis, the combination of sub-antinociceptive doses of peptides demonstrated additive antinociception in rats with a nerve ligation and in the formalin test, without apparent adverse side effects. In a model of neuropathic spinal cord injury pain, which is clinically difficult to treat, the combination of conantokin-G and omega-conotoxin MVIIA resulted in robust synergistic antinociception. These data suggest that a combination of these peptides may be analgesic across diverse clinical pains with limited untoward side effects, and particularly potent for reducing spinal cord injury pain.

Ziconotide: an update and review

BACKGROUND

Ziconotide is the only N-type calcium channel blocker approved by the US FDA for the treatment of chronic pain. The approved indication is for the management of severe chronic pain in patients for whom intrathecal therapy is warranted and who are intolerant of or refractory to other treatments such as systemic analgesics, adjunctive therapies or intrathecal morphine.

OBJECTIVE

The purpose of this article was to review the available safety, efficacy and dosing information for ziconotide.

METHODS

The sources searched for literature from 1980 to January 2008 included Pub Med, MEDLINE and PREMEDLINE using the words ziconotide, conotoxins and pain.

RESULTS/CONCLUSION

Ziconotide is administered intrathecally by infusion pump to block nociceptive signal transmission in the spinal cord. It is a synthetic neuroactive peptide equivalent to the omega conotoxin MVIIA, a constituent of the venom of the fish-hunting marine snail Conus magus. It is highly potent, has a steep dose-response curve, a slow onset of action and a narrow margin of safety and responses to dose adjustments are slow. Patients receiving ziconotide should be under the care of physicians experienced in the management of intrathecal infusion therapy for pain control and should have convenient access to medical facilities.