Effectiveness and Safety of Intrathecal Ziconotide: Interim Analysis of the Patient Registry of Intrathecal Ziconotide Management (PRIZM)

Post-mastectomy Pain Syndrome: A Review Article and Emerging Treatment Modalities

Post-mastectomy pain syndrome (PMPS) is a syndrome broadly applied to the development of chronic pain after surgical breast intervention (i.e., lumpectomy and mastectomy). The incidence of PMPS is likely underreported, and this has contributed to a paucity of high-level evidence related to the treatment of the aforementioned condition. A drive to reduce the burden of opioid use has led to pain management physicians trialing a variety of strategies to help patients manage PMPS. This review discusses the latest evidence behind treatment options for PMPS, exploring medications as well as interventional techniques (e.g., nerve blocks, radiofrequency ablation, neuromodulation, and intrathecal drug delivery systems). Recent advances in neuromodulation technology are of particular interest here due to the well-localized nature of PMPS-related pain and the specificity with which modern neuromodulation techniques can generate an effect. Finally, the review proposes a framework with which to approach the care of patients with PMPS, with a specific emphasis on the early consideration of neuromodulation techniques along with functional and physical therapy to reduce patient medication burden and improve overall quality of life.

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.

Intrathecal Drug Delivery: Advances and Applications in the Management of Chronic Pain Patient

Advances in our understanding of the biology of spinal systems in organizing and defining the content of exteroceptive information upon which higher centers define the state of the organism and its role in the regulation of somatic and automatic output, defining the motor response of the organism, along with the unique biology and spatial organization of this space, have resulted in an increased focus on therapeutics targeted at this extracranial neuraxial space. Intrathecal (IT) drug delivery systems (IDDS) are well-established as an effective therapeutic approach to patients with chronic non-malignant or malignant pain and as a tool for management of patients with severe spasticity and to deliver therapeutics that address a myriad of spinal pathologies. The risk to benefit ratio of IDD makes it a useful interventional approach. While not without risks, this approach has a significant therapeutic safety margin when employed using drugs with a validated safety profile and by skilled practioners. The present review addresses current advances in our understanding of the biology and dynamics of the intrathecal space, therapeutic platforms, novel therapeutics, delivery technology, issues of safety and rational implementation of its therapy, with a particular emphasis upon the management of pain.

Computational design of peptides to target NaV1.7 channel with high potency and selectivity for the treatment of pain

The voltage-gated sodium Na_V1.7 channel plays a key role as a mediator of action potential propagation in C-fiber nociceptors and is an established molecular target for pain therapy. ProTx-II is a potent and moderately selective peptide toxin from tarantula venom that inhibits human Na_V1.7 activation. Here we used available structural and experimental data to guide Rosetta design of potent and selective ProTx-II-based peptide inhibitors of human Na_V1.7 channels. Functional testing of designed peptides using electrophysiology identified the PTx2-3127 and PTx2-3258 peptides with IC₅₀s of 7 nM and 4 nM for hNa_V1.7 and more than 1000-fold selectivity over human Na_V1.1, Na_V1.3, Na_V1.4, Na_V1.5, Na_V1.8, and Na_V1.9 channels. PTx2-3127 inhibits Na_V1.7 currents in mouse and human sensory neurons and shows efficacy in rat models of chronic and thermal pain when administered intrathecally. Rationally designed peptide inhibitors of human Na_V1.7 channels have transformative potential to define a new class of biologics to treat pain.

Structure of human Cav2.2 channel blocked by the painkiller ziconotide

The neuronal-type (N-type) voltage-gated calcium (Ca_v) channels, which are designated Ca_v2.2, have an important role in the release of neurotransmitters^1-3. Ziconotide is a Ca_v2.2-specific peptide pore blocker that has been clinically used for treating intractable pain^4-6. Here we present cryo-electron microscopy structures of human Ca_v2.2 (comprising the core α1 and the ancillary α2δ-1 and β3 subunits) in the presence or absence of ziconotide. Ziconotide is thoroughly coordinated by helices P1 and P2, which support the selectivity filter, and the extracellular loops (ECLs) in repeats II, III and IV of α1. To accommodate ziconotide, the ECL of repeat III and α2δ-1 have to tilt upward concertedly. Three of the voltage-sensing domains (VSDs) are in a depolarized state, whereas the VSD of repeat II exhibits a down conformation that is stabilized by Ca_v2-unique intracellular segments and a phosphatidylinositol 4,5-bisphosphate molecule. Our studies reveal the molecular basis for Ca_v2.2-specific pore blocking by ziconotide and establish the framework for investigating electromechanical coupling in Ca_v channels.

Short-Term Outcomes of a High-Volume, Low-Concentration Bolus Starting Dose Technique With Ziconotide: A Case Series

Background and Objectives

There have been numerous recommendations for a starting dose of intrathecal ziconotide. The therapy remains underutilized partially due to reports of inefficacy and/or intolerance. This study describes short‐term outcomes of a high‐volume, low‐concentration bolus (HVLC‐B) ziconotide starting dose technique for patients with chronic spine pain. Intrathecal pumps are available with a Patient Therapy Manager (PTM), or patient‐controlled intrathecal bolus device. Commonly published recommendations for a bolus dose has been 10% of the daily dose. This article describes an inversion of the traditional 10% rule‐of‐thumb. This article describes using the basal rate at a lowest programmable dose and utilizing the bolus for the majority of the medication delivery. Such an inversion may be considered a high volume bolus. The lowest commercially available concentration of ziconotide from the manufacturer is 25 mcg/mL. Pope and Deer (Neuromodulation, 18, 414–420 [2015]) described use of a dilution down to 5 mcg/mL. For purposes of this article, such dilutions to one‐fifth of the commercially available solution are considered sufficiently dilute to qualify for the term “low concentration.” Furthermore, the patients in this analysis received dilutions down to one‐fiftieth of the lowest commercially available solution.

Materials and Methods

A case series of patients with chronic spine pain with or without radicular pain received a starting dose intrathecal ziconotide regimen based on a specific HVLC‐B technique. Efficacy, tolerability, and pump settings are reported and analyzed.

Results

In total, 17 patients were identified who started ziconotide with the specified HVLC‐B starting regimen. One of the 17 patients reported side effects that led to discontinuation of the therapy, although the side effect was not typical of ziconotide but rather likely attributable to other medications the patient was taking. Fifteen of the 17 reported improved pain control with intrathecal ziconotide. Sixteen of the 17 patients remained on intrathecal ziconotide throughout the 4.7‐month average follow‐up period. One patient who failed to obtain pain relief chose to remain on the therapy because of reported resolution of lower limb numbness.

Conclusions

The HVLC‐B starting regimen was effective and well tolerated in this short‐term study of patients with chronic spine pain. More studies are needed to better elucidate long‐term outcomes in larger patient populations.

Intrathecal pain management with ziconotide: Time for consensus?

This article summarizes recommendations made by six pain specialists who discussed the rationale for ziconotide intrathecal analgesia (ITA) and the requirement for evidence-based guidance on its use, from a European perspective. Riemser Pharma GmbH (Greifswald, Germany), which holds the European marketing authorization for ziconotide, hosted the meeting. The group agreed that ITA is under-used in Europe, adding that ziconotide ITA has potential to be a first-line alternative to morphine; both are already first-line options in the USA. Ziconotide ITA (initiated using a low-dose, slow-titration approach) is suitable for many patients with noncancer- or cancer-related chronic refractory pain and no history of psychosis. Adopting ziconotide as first-line ITA could reduce opioid usage in these patient populations. The group advocated a risk-reduction strategy for all candidate patients, including compulsory prescreening for neuropsychosis, and requested US-European alignment of the licensed starting dose for ziconotide: the low-and-slow approach practiced in the USA has a better tolerability profile than the fixed high starting dose licensed in Europe. Of note, an update to the European Summary of Product Characteristics is anticipated in early 2021. The group acknowledged that the Polyanalgesic Consensus Conference (PACC) treatment algorithms for ziconotide ITA provide useful guidance, but recommendations tailored specifically for European settings are required. Before a consensus process can formally begin, the group called for additional European prospective studies to investigate ziconotide in low-and-slow dosing strategies, in different patient settings. Such data would enable European guidance to have the most appropriate evidence at its core.

[What became of Prialt®? : Observational study on the use of ziconotide in the treatment of chronic pain]

Hintergrund

Prialt® ist seit Februar 2005 von der europäischen Arzneimittelbehörde zugelassen und ist neben Morphin das einzige Analgetikum, welches über die offizielle Marktzulassung in der intrathekalen Schmerztherapie verfügt. Da es nicht über Opioidrezeptoren wirkt, galt es zum Zeitpunkt der Markteinführung als nebenwirkungs- und risikoärmer in der Behandlung chronischer Schmerzen als Morphin. Trotzdem gilt es noch heute als Orphan Drug und Studien über den Langzeiteinsatz und hierunter aufgetretene Nebenwirkungen sind rar.

Fragestellung

Welchen Stellenwert nimmt Prialt® verglichen mit anderen intrathekal verabreichten Analgetika ein? Wie wirken sich die Startdosis und die Geschwindigkeit der Aufdosierung auf die schmerzlindernde Wirkung und das Auftreten von Nebenwirkungen in der Langzeittherapie aus?

Material und Methoden

Zum einen wurden anhand von Arztbriefen retrospektiv alle Patienten erfasst, die zwischen Februar 2005 und dem Ende des Beobachtungszeitraums im Oktober 2018 Ziconotid in Monotherapie in der Neurochirurgie des Universitätsklinikums Jena erhielten. Zum anderen wurden diese Patienten anhand eines erstellten Fragebogens hinsichtlich ihrer Erfahrung mit Ziconotid befragt.

Ergebnisse

Bei allen zwölf in die Studie eingeschlossenen Teilnehmern kam es zu mindestens einer Arzneimittelnebenwirkung. Am häufigsten wurde über Vergesslichkeit und Sensibilitätsstörungen mit jeweils 25 % berichtet. Ein Drittel der Patienten musste die Behandlung aufgrund von Nebenwirkungen beenden. Die mittlere Initialdosis betrug 1,98 µg/Tag.

Diskussion

Trotz leitliniengerechter Behandlung hat sich Ziconotid am Universitätsklinikum Jena nicht gegen Morphin und andere Opioidanalgetika in der intrathekalen Schmerztherapie durchgesetzt. Die Gründe hierfür sind vielfältig, wobei die enge therapeutische Breite, das häufige Auftreten von Nebenwirkungen und die schwierige therapeutische Handhabung, vor allem im ambulanten Setting, von besonderer Bedeutung sind.

Effect of First-Line Ziconotide Intrathecal Drug Therapy for Neuropathic Pain on Disability, Emotional Well-Being, and Pain Catastrophizing

BACKGROUND

Previous studies have shown decreased pain scores with ziconotide as a first-line agent for intrathecal drug therapy (IDT). Subset analysis suggests that patients with neuropathic pain have greater improvement. We prospectively examine the role of first-line ziconotide IDT on the tridimensional pain experience in ziconotide IDT-naive patients with neuropathic pain.

METHODS

We included patients who underwent a successful ziconotide trial and were scheduled for standard-of-care IDT pump placement. Scores were collected at baseline and latest follow-up for the following measures: Short-Form 36 (SF-36), Oswestry Disability Index (ODI), Beck Depression Inventory, and Pain Catastrophizing Scale (PCS). Numeric rating scale (NRS) scores were also collected at each follow-up visit to monitor patients' pain levels and to guide ziconotide dose titration. Responders were identified as patients who had a previously established minimum clinically important difference of a ≥1.2-point reduction in NRS current scores.

RESULTS

Eleven of 14 patients completed long-term follow-up. There were 7 responders based on NRS minimum clinically important difference. At a mean (±standard error of the mean) follow-up of 10.91 ± 0.70 months, SF-36 emotional well-being (P = 0.04), SF-36 pain (P = 0.02), and ODI (P = 0.03) significantly improved for the entire cohort and in responders (SF-36 emotional well-being, P = 0.01; SF-36 pain, P = 0.04; ODI, P = 0.02). PCS-Rumination (P = 0.02), PCS-Helplessness (P = 0.02), and PCS-Total (P = 0.003) scores improved significantly for responders only.

CONCLUSIONS

We show that ziconotide IDT improves pain as well as emotional components and function. Our study adds prospective evidence to the literature on IDT for neuropathic pain, specifically its role in improving disability, emotional well-being, and catastrophizing.

Effectiveness and Safety of Intrathecal Ziconotide: Final Results of the Patient Registry of Intrathecal Ziconotide Management (PRIZM)

Background and Objectives

The Patient Registry of Intrathecal Ziconotide Management evaluated the long-term effectiveness and safety of intrathecal ziconotide.

Methods

The study was a prospective, multicenter observational study of intrathecal ziconotide in US clinical practice. Patients were adults with severe chronic pain that warranted intrathecal therapy. Ziconotide was initiated as the single agent in the pump; however, other intrathecal medications were permitted. The primary efficacy outcome was ≥30% reduction in numeric pain rating scale score from baseline at week 12. A secondary outcome was patient global impression of change. Adverse events were solicited at each visit.

Results

The registry enrolled 93 patients. Seventy-four and 28 patients completed 12 weeks and 18 months of treatment, respectively. In the overall patient population, 17.4% had ≥30% pain reduction from baseline at week 12, with a mean reduction in pain of 10.9%. At month 18, 38.5% of patients had ≥30% pain reduction from baseline, with a mean pain reduction of 24.7%. Patient-rated improvement was reported in 67% of patients at week 12 and 71% at month 18. Almost all patients experienced adverse events, the most common of which were nausea (25.8%), confusional state (22.6%), and dizziness (20.4%).

Conclusions

Final study analyses showed that intrathecal ziconotide provided clinically meaningful pain relief in 17.4% and 38.5% of patients at week 12 and month 18, respectively. At these same time points, patient-rated improvement was reported in at least two-thirds of patients. The safety profile was consistent with that listed in the ziconotide prescribing information.

Pain medicine fellow neuromodulation surgical skill assessment tool: a pilot

OBJECTIVE

Spinal cord stimulation (SCS) is an evidence-based therapy for the treatment of refractory pain. Current American College of Graduate Medical Education requirements for pain medicine fellowship graduation include observation of five neuromodulation cases. Matriculating fellows have varying degrees of technical skill, training, and experience. The purpose of this study was to use an innovative skill-based assessment tool using the validated Zwisch scale to evaluate fellow surgical performance during SCS cases.

DESIGN

Cross-sectional survey SETTING: Mayo Clinic, Rochester, Minnesota.

SUBJECTS

Consultant faculty (10) in the Division of Pain Medicine and pain medicine fellows (5).

METHODS

A list of faculty-driven neuromodulation surgical objectives was formed and a rubric was created that focused on technical approach, imaging, epidural access and wound closure. Consultants who perform surgical cases were instructed to use the Zwisch scale as a guide to evaluate fellow surgical performance during a neuromodulation case. Faculty and fellows were surveyed before and after implementation of the tool to determine their satisfaction with use of the skill assessment tool.

RESULTS

The consultants reported they were more satisfied, consistent, and efficient with feedback provided to the trainee on every aspect of neuromodulation surgical cases. The improvement was most significant during the fellows' intraoperative skill assessment. The fellows indicated increased satisfaction, improved communication, and increased efficiency of feedback when the tool was utilized. The fellows reported greater intraoperative skill assessment and consistency of feedback provided.

CONCLUSIONS

The diverse nature of primary specialty backgrounds observed in pain medicine fellowship training offers a unique opportunity to assess and improve fellow skill and surgical competence in the field of neuromodulation. Both faculty and fellows reported improved satisfaction, consistency and efficiency with feedback provided. Importantly, this pilot project observed that implementation of a skill assessment tool was beneficial for both the faculty and fellow as the feedback received was viewed as strongly beneficial to the educational experience.

Intrathecal Therapy for Chronic Pain: A Review of Morphine and Ziconotide as Firstline Options

Objectives

To evaluate the evidence for morphine and ziconotide as firstline intrathecal (IT) analgesia agents for patients with chronic pain.

Methods

Medline was searched (through July 2017) for “ziconotide” or “morphine” AND “intrathecal” AND “chronic pain,” with results limited to studies in human populations.

Results

The literature supports the use of morphine (based primarily on noncontrolled, prospective, and retrospective studies) and ziconotide (based on randomized controlled trials and prospective observational studies) as first-choice IT therapies. The 2016 Polyanalgesic Consensus Conference (PACC) guidelines recommended both morphine and ziconotide as firstline IT monotherapy for localized and diffuse chronic pain of cancer-related and non–cancer-related etiologies; however, one consensus point emphasized ziconotide use, unless contraindicated, as firstline IT therapy in patients with chronic non–cancer-related pain. Initial IT therapy choice should take into consideration individual patient characteristics (e.g., pain location, response to previous therapies, comorbid medical conditions, psychiatric history). Trialing is recommended to assess medication efficacy and tolerability. For both morphine and ziconotide, the PACC guidelines recommend conservative initial dosing strategies. Due to its narrow therapeutic window, ziconotide requires careful dose titration. Ziconotide is contraindicated in patients with a history of psychosis. IT morphine administration may be associated with serious side effects (e.g., respiratory depression, catheter tip granuloma), require dose increases, and cause dependence over time.

Conclusion

Based on the available evidence, morphine and ziconotide are recommended as firstline IT monotherapy for cancer-related and non–cancer-related pain. The choice of first-in-pump therapy should take into consideration patient characteristics and the advantages and disadvantages of each medication.

Marine Toxins and Nociception: Potential Therapeutic Use in the Treatment of Visceral Pain Associated with Gastrointestinal Disorders

Visceral pain, of which the pathogenic basis is currently largely unknown, is a hallmark symptom of both functional disorders, such as irritable bowel syndrome, and inflammatory bowel disease. Intrinsic sensory neurons in the enteric nervous system and afferent sensory neurons of the dorsal root ganglia, connecting with the central nervous system, represent the primary neuronal pathways transducing gut visceral pain. Current pharmacological therapies have several limitations, owing to their partial efficacy and the generation of severe adverse effects. Numerous cellular targets of visceral nociception have been recognized, including, among others, channels (i.e., voltage-gated sodium channels, VGSCs, voltage-gated calcium channels, VGCCs, Transient Receptor Potential, TRP, and Acid-sensing ion channels, ASICs) and neurotransmitter pathways (i.e., GABAergic pathways), which represent attractive targets for the discovery of novel drugs. Natural biologically active compounds, such as marine toxins, able to bind with high affinity and selectivity to different visceral pain molecular mediators, may represent a useful tool (1) to improve our knowledge of the physiological and pathological relevance of each nociceptive target, and (2) to discover therapeutically valuable molecules. In this review we report the most recent literature describing the effects of marine toxin on gastrointestinal visceral pain pathways and the possible clinical implications in the treatment of chronic pain associated with gut diseases.

Near-resolution of persistent idiopathic facial pain with low-dose lumbar intrathecal ziconotide: a case report

Purpose

Persistent idiopathic facial pain (PIFP) is a poorly defined and debilitating chronic pain state with a challenging and often inadequate treatment course. This is the first case report identifying the novel use of low-dose lumbar intrathecal ziconotide to successfully treat PIFP with nearly complete resolution of pain and minimal to no side effects.

Methods

The patient was a 37 year-old female whose PIFP was refractory to multimodal medication management and multiple neurovascular surgical interventions. A single-shot lumbar intrathecal trial of ziconotide (2.5 mL, equivalent 2.5 μg) was injected when she was at her baseline pain level — VAS 7/10. She received complete resolution of her pain for about 9 hours, concordant with ziconotide’s half-life. She was subsequently implanted with a lumbar intrathecal delivery system.

Results

The patient experienced complete resolution of her facial pain with a single-shot intrathecal trial of ziconotide. The intrathecal pump system has provided nearly complete (VAS 1/10) pain relief. Two flares of pain occurred 10 and 18 months after pump placement, which subsequently resolved after increasing the ziconotide dose by 0.5 μg/day on each occasion. The patient is currently maintained on a dose of 2.0 μg/day and is pain-free.

Conclusion

This is the first case report describing the use of a single-shot lumbar intrathecal trial of ziconotide and subsequent placement of lumbar (as opposed to thoracic) intrathecal ziconotide pump for PIFP. A single-injection intrathecal trial is a low-risk, viable option for patients with this debilitating and frustrating pain condition. Successful trials and subsequent intrathecal pump placement with ziconotide may supplant multimodal medication management and/or invasive orofacial surgical intervention for PIFP.

T-type Calcium Channels in Health and Disease

Low Voltage-Activated (LVA) T-type calcium channels are characterized by transient current and Low Threshold Spikes (LTS) that trigger neuronal firing and oscillatory behavior. Combined with their preferential localization in dendrites and their specific "window current", T-type calcium channels are considered to be key players in signal amplification and synaptic integration. Assisted by the emerging pharmacological tools, the structural determinants of channel gating and kinetics, as well as novel physiological and pathological functions of T-type calcium channels, are being uncovered. In this review, we provide an overview of structural determinants in T-type calcium channels, their involvement in disorders and diseases, the development of novel channel modulators, as well as Structure-Activity Relationship (SAR) studies that lead to rational drug design.

Mirogabalin and emerging therapies for diabetic neuropathy

There are currently no approved disease-modifying therapies for diabetic neuropathy, and there are only 3 US Food and Drug Administration-approved therapies (pregabalin, duloxetine, and tapentadol) for painful diabetic neuropathy. They each have moderate efficacy with adverse effects limiting optimal dose titration. There is a considerable need for new therapies for the management of painful diabetic neuropathy. We reviewed the potential role of mirogabalin, which like gabapentin and pregabalin modulates the alpha-2/delta-1 subunit of the voltage-gated calcium channel, allowing the influx of calcium and release of neurotransmitters at the synaptic cleft in the central nervous system and spinal cord. It has shown efficacy and good tolerability in a Phase II study in diabetic painful neuropathy and based on the results of two Phase III clinical trials in diabetic painful neuropathy and post-herpetic neuralgia, Daiichi Sankyo submitted a marketing application for neuropathic pain in Japan in February 2018. We have also reviewed potential new therapies, currently in Phase II clinical trials that may modify disease and/or relieve neuropathic pain through novel modes of action.

Role of primary care physicians in intrathecal pain management: a narrative review of the literature

OBJECTIVES

The majority of patients seeking medical care for chronic pain consult a primary care physician (PCP). Because systemic opioids are commonly prescribed to patients with chronic pain, PCPs are attempting to balance the competing priorities of providing adequate pain relief while reducing risks for opioid misuse and overdose. It is important for PCPs to be aware of pain management strategies other than systemic opioid dose escalation when patients with chronic pain fail to respond to conservative therapies and to initiate a multimodal treatment plan.

METHODS

The Medline database and evidence-based treatment guidelines were searched to identify publications on intrathecal (IT) therapy for the management of chronic pain. Selection of publications relevant to PCPs was based on the authors' clinical and research expertise.

RESULTS

IT administration delivers analgesic medication directly into the cerebrospinal fluid, avoiding first-pass effect and bypassing the blood-brain barrier, thereby requiring lower medication doses. Morphine, a µ-opioid receptor agonist, and ziconotide, a non-opioid, selective N-type calcium channel blocker, are the only analgesics approved by the US Food and Drug Administration to treat chronic refractory pain by the IT route. Patients who are potential candidates for IT therapy may benefit from evaluation by an interventional pain physician. PCPs can play an important role in patient selection and referral for IT therapy and provide ongoing collaborative care for patients receiving IT therapy, including monitoring for efficacy and adverse events and facilitating communication with the treating specialist.

CONCLUSIONS

Collaboration between PCPs and pain specialists may improve outcomes of and patient satisfaction with IT therapy and other interventional treatments.

Effects of opioid and nonopioid analgesics on canine wheal formation and cultured human mast cell degranulation

Mast cell (MC) degranulation has been implicated in the side effect profile of a variety of clinically useful agents. Thus, after intrathecal delivery, formation of space-occupying, meningeally-derived masses may be related to local MC degranulation. We systematically characterized degranulating effects of opioid and nonopioid analgesics on cutaneous flares in the dog and in primary human MC (hMC) cultures.

METHODS

Dogs were anesthetized with IV propofol and received intradermal (ID) injections (50μL). Flare diameters were measured at 30min. Drugs showing flare responses were tested after intramuscular (IM) cromolyn (10mg/kg), a MC stabilizer. Human primary MCs (human cord blood CD34⁺/CD45⁺ cells) were employed and β-hexosaminidase in cell-free supernatants were measured to assess degranulation.

RESULTS

A significant skin flare for several classes of agents was observed including opioids, ziconotide, ketamine, ST-91, neostigmine, adenosine, bupivacaine, lidocaine, MK-801 and 48/80. Tizanidine, fentanyl, alfentanil, gabapentin and baclofen produced no flare. Flare produced by all ID agents, except adenosine, bupivacaine and lidocaine, was reduced by cromolyn. Naloxone had no effect upon opiate or 48/80 evoked flares. In hMC studies, 48/80 resulted in a concentration-dependent release of β-hexosaminidase. The rank order of drug-induced hMC β-hexosaminidase release was similar to that for flares.

CONCLUSIONS

A variety of therapeutically useful drugs degranulate MCs. This action may account for side effects such as the intrathecal granuloma resulting from spinally-delivered opioids. This degranulating effect may be useful in predicting potential intrathecal toxicity in the development of novel agents.

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.