Intrathecal ziconotide in the treatment of refractory pain in patients with cancer or AIDS: a randomized controlled trial

Intrathecal pain management: a team-based approach

Objective

Physician assistants (PAs), nurse practitioners (NPs), and registered nurses (RNs) provide professional services on pain management teams. This review provides an overview of the practical management of chronic pain with intrathecal (IT) therapy using an interprofessional approach (eg, physicians and other health care professionals), with a focus on the contributions of PAs, NPs, and RNs.

Methods

Narrative review based on literature searches of the Medline database and treatment guidelines on the use of IT therapy in the management of patients with chronic pain.

Results

The specific roles and responsibilities of PAs, NPs, and RNs in the management of patients receiving IT therapy vary by practice. In many pain treatment centers, PAs, NPs, and RNs are responsible for patient education, postimplant maintenance, and ongoing supportive care of patients receiving IT therapy. Topics that we address include patient selection, patient expectations and goal setting, medication selection, outcome assessment, and treatment adjustment. Currently, morphine and ziconotide (a nonopioid, selective N-type calcium channel blocker) are the only agents approved by the US Food and Drug Administration for IT analgesia. We provide relevant information on the dosing, titration, and adverse effect management of these medications for PAs, NPs, and RNs responsible for administering IT therapy.

Conclusion

PAs, NPs, and RNs are valuable members of IT pain management teams. Treatment success requires ongoing monitoring of efficacy and adverse effects, with corresponding adjustments to medication selection and dosing, in addition to good communication among the health care professionals involved in patient care.

Discovery and mode of action of a novel analgesic β-toxin from the African spider Ceratogyrus darlingi

Spider venoms are rich sources of peptidic ion channel modulators with important therapeutical potential. We screened a panel of 60 spider venoms to find modulators of ion channels involved in pain transmission. We isolated, synthesized and pharmacologically characterized Cd1a, a novel peptide from the venom of the spider Ceratogyrus darlingi. Cd1a reversibly paralysed sheep blowflies (PD₅₀ of 1318 pmol/g) and inhibited human Ca_v2.2 (IC₅₀ 2.6 μM) but not Ca_v1.3 or Ca_v3.1 (IC₅₀ > 30 μM) in fluorimetric assays. In patch-clamp electrophysiological assays Cd1a inhibited rat Ca_v2.2 with similar potency (IC₅₀ 3 μM) without influencing the voltage dependence of Ca_v2.2 activation gating, suggesting that Cd1a doesn’t act on Ca_v2.2 as a classical gating modifier toxin. The Cd1a binding site on Ca_v2.2 did not overlap with that of the pore blocker ω-conotoxin GVIA, but its activity at Ca_v2.2-mutant indicated that Cd1a shares some molecular determinants with GVIA and MVIIA, localized near the pore region. Cd1a also inhibited human Na_v1.1–1.2 and Na_v1.7–1.8 (IC₅₀ 0.1–6.9 μM) but not Na_v1.3–1.6 (IC₅₀ > 30 μM) in fluorimetric assays. In patch-clamp assays, Cd1a strongly inhibited human Na_v1.7 (IC₅₀ 16 nM) and produced a 29 mV depolarising shift in Na_v1.7 voltage dependence of activation. Cd1a (400 pmol) fully reversed Na_v1.7-evoked pain behaviours in mice without producing side effects. In conclusion, Cd1a inhibited two anti-nociceptive targets, appearing to interfere with Ca_v2.2 inactivation gating, associated with the Ca_v2.2 α-subunit pore, while altering the activation gating of Na_v1.7. Cd1a was inactive at some of the Na_v and Ca_v channels expressed in skeletal and cardiac muscles and nodes of Ranvier, apparently contributing to the lack of side effects at efficacious doses, and suggesting potential as a lead for development of peripheral pain treatments.

Changes in Ionic Conductance Signature of Nociceptive Neurons Underlying Fabry Disease Phenotype

The first symptom arising in many Fabry patients is neuropathic pain due to changes in small myelinated and unmyelinated fibers in the periphery, which is subsequently followed by a loss of sensory perception. Here we studied changes in the peripheral nervous system of Fabry patients and a Fabry mouse model induced by deletion of α-galactosidase A (Gla^-/0). The skin innervation of Gla^-/0 mice resembles that of the human Fabry patients. In Fabry diseased humans and Gla^-/0 mice, we observed similar sensory abnormalities, which were also observed in nerve fiber recordings in both patients and mice. Electrophysiological recordings of cultured Gla^-/0 nociceptors revealed that the conductance of voltage-gated Na⁺ and Ca²⁺ currents was decreased in Gla^-/0 nociceptors, whereas the activation of voltage-gated K⁺ currents was at more depolarized potentials. Conclusively, we have observed that reduced sensory perception due to small-fiber degeneration coincides with altered electrophysiological properties of sensory neurons.

Effect of the spider toxin Tx3-3 on spinal processing of sensory information in naive and neuropathic rats: an in vivo electrophysiological study

The P/Q- and R-type voltage-gated calcium channel blocker Tx3-3 inhibits dorsal horn neuronal response of rats with greater potency after nerve injury.

Introduction:

Drugs that counteract nociceptive transmission in the spinal dorsal horn preferentially after nerve injury are being pursued as possible neuropathic pain treatments. In a previous behavioural study, the peptide toxin Tx3-3, which blocks P/Q- and R-type voltage-gated calcium channels, was effective in neuropathic pain models.

Objectives:

In the present study, we aimed to investigate the effect of Tx3-3 on dorsal horn neuronal responses in rats under physiological conditions and neuropathic pain condition induced by spinal nerve ligation (SNL).

Methods:

In vivo electrophysiological recordings of dorsal horn neuronal response to electrical and natural (mechanical and thermal) stimuli were made in rats under normal physiological state (naive rats) or after the SNL model of neuropathic pain.

Results:

Tx3-3 (0.3–100 pmol/site) exhibited greater inhibitory effect on electrical-evoked neuronal response of SNL rats than naive rats, inhibiting nociceptive C-fibre and Aδ-fibre responses only in SNL rats. The wind-up of neurones, a measurement of spinal cord hyperexcitability, was also more susceptible to a dose-related inhibition by Tx3-3 after nerve injury. Moreover, Tx3-3 exhibited higher potency to inhibit mechanical- and thermal-evoked neuronal response in conditions of neuropathy.

Conclusion:

Tx3-3 mediated differential inhibitory effect under physiological and neuropathic conditions, exhibiting greater potency in conditions of neuropathic pain.

Progress and challenges in the optimization of toxin peptides for development as pain therapeutics

The number of new toxin peptide discoveries has been rapidly growing in the past few decades. Because of progress in proteomics, sequencing technologies, and high throughput bioassays, the search for new toxin peptides from venom collections and potency optimization has become manageable. However, to date, only six toxin peptide-derived therapeutics have been approved by the USFDA, with only one, ziconotide, for a pain indication. The challenge of venom-derived peptide therapeutic development remains in improving selectivity to the target and more importantly, in delivery of these peptides to the sites of action in the central and peripheral nervous system. In this review, we highlight peptide toxins that target major therapeutic targets for pain and discuss the challenges of developing toxin peptides as potential therapeutics.

(S)-lacosamide inhibition of CRMP2 phosphorylation reduces postoperative and neuropathic pain behaviors through distinct classes of sensory neurons identified by constellation pharmacology

Chronic pain affects the life of millions of people. Current treatments have deleterious side effects. We have advanced a strategy for targeting protein interactions which regulate the N-type voltage-gated calcium (CaV2.2) channel as an alternative to direct channel block. Peptides uncoupling CaV2.2 interactions with the axonal collapsin response mediator protein 2 (CRMP2) were antinociceptive without effects on memory, depression, and reward/addiction. A search for small molecules that could recapitulate uncoupling of the CaV2.2-CRMP2 interaction identified (S)-lacosamide [(S)-LCM], the inactive enantiomer of the Food and Drug Administration-approved antiepileptic drug (R)-lacosamide [(R)-LCM, Vimpat]. We show that (S)-LCM, but not (R)-LCM, inhibits CRMP2 phosphorylation by cyclin dependent kinase 5, a step necessary for driving CaV2.2 activity, in sensory neurons. (S)-lacosamide inhibited depolarization-induced Ca influx with a low micromolar IC50. Voltage-clamp electrophysiology experiments demonstrated a commensurate reduction in Ca currents in sensory neurons after an acute application of (S)-LCM. Using constellation pharmacology, a recently described high content phenotypic screening platform for functional fingerprinting of neurons that uses subtype-selective pharmacological agents to elucidate cell-specific combinations (constellations) of key signaling proteins that define specific cell types, we investigated if (S)-LCM preferentially acts on certain types of neurons. (S)-lacosamide decreased the dorsal root ganglion neurons responding to mustard oil, and increased the number of cells responding to menthol. Finally, (S)-LCM reversed thermal hypersensitivity and mechanical allodynia in a model of postoperative pain, and 2 models of neuropathic pain. Thus, using (S)-LCM to inhibit CRMP2 phosphorylation is a novel and efficient strategy to treat pain, which works by targeting specific sensory neuron populations.

Bioactive Peptide of Marine Origin for the Prevention and Treatment of Non-Communicable Diseases

Non-communicable diseases (NCD) are the leading cause of death and disability worldwide. The four main leading causes of NCD are cardiovascular diseases, cancers, respiratory diseases and diabetes. Recognizing the devastating impact of NCD, novel prevention and treatment strategies are extensively sought. Marine organisms are considered as an important source of bioactive peptides that can exert biological functions to prevent and treatment of NCD. Recent pharmacological investigations reported cardio protective, anticancer, antioxidative, anti-diabetic, and anti-obesity effects of marine-derived bioactive peptides. Moreover, there is available evidence supporting the utilization of marine organisms and its bioactive peptides to alleviate NCD. Marine-derived bioactive peptides are alternative sources for synthetic ingredients that can contribute to a consumer's well-being, as a part of nutraceuticals and functional foods. This contribution focus on the bioactive peptides derived from marine organisms and elaborates its possible prevention and therapeutic roles in NCD.

Targeting human Mas-related G protein-coupled receptor X1 to inhibit persistent pain

Human Mas-related G protein-coupled receptor X1 (MRGPRX1) is a promising target for pain inhibition, mainly because of its restricted expression in nociceptors within the peripheral nervous system. However, constrained by species differences across Mrgprs, drug candidates that activate MRGPRX1 do not activate rodent receptors, leaving no responsive animal model to test the effect on pain in vivo. Here, we generated a transgenic mouse line in which we replaced mouse Mrgprs with human MrgprX1 This humanized mouse allowed us to characterize an agonist [bovine adrenal medulla 8-22 (BAM8-22)] and a positive allosteric modulator (PAM), ML382, of MRGPRX1. Cellular studies suggested that ML382 enhances the ability of BAM8-22 to inhibit high-voltage-activated Ca²⁺ channels and attenuate spinal nociceptive transmission. Importantly, both BAM8-22 and ML382 effectively attenuated evoked, persistent, and spontaneous pain without causing obvious side effects. Notably, ML382 by itself attenuated both evoked pain hypersensitivity and spontaneous pain in MrgprX1 mice after nerve injury without acquiring coadministration of an exogenous agonist. Our findings suggest that humanized MrgprX1 mice provide a promising preclinical model and that activating MRGPRX1 is an effective way to treat persistent pain.

The Pharmacology of Spinal Opioids and Ziconotide for the Treatment of Non-Cancer Pain

Background

Intrathecal drug delivery has undergone a revitalization following a better understanding of this delivery route and its pharmacokinetics. Driven by patient safety and outcomes, clinicians are motivated to rethink the traditional spinal infusion pump patient selection criteria and indications. We review the current understanding of the pharmacology of commonly employed intrathecal agents and the clinical relevance.

Methods

Search strategies for data acquisition included Medline database, PubMed, Google scholar, along with international and national professional meeting content, with key words including pharmacology of opioids, intrathecal therapy, ziconotide, pharmacokinetics, and intrathecal drug delivery. The search results were limited to the English language.

Results

Over 300 papers were identified. The literature was condensed and digested to evaluate the most commonly used medications in practice, sto serve as a foundation for review. We review on-label medications: ziconotide and morphine, and off label medications including fentanyl, sufentail, and hydromorphine.

Conclusion

Intrathecal therapy has level-one evidence for use for malignant pain and nonmalignant pain, with continued cost savings and improved safety. To most effectively serve our patients, a clear appreciation for the pharmacology of these commonly employed medication is paramount..

The Polyanalgesic Consensus Conference (PACC): Recommendations for Trialing of Intrathecal Drug Delivery Infusion Therapy

INTRODUCTION

Intrathecal (IT) drug infusion is an appropriate and necessary tool in the algorithm to treat refractory cancer and noncancer pain. The decision-making steps/methodology for selecting appropriate patients for implanted targeted drug delivery systems is controversial and complicated. Therefore, a consensus on best practices for determining appropriate use of IT drug infusion may involve testing/trialing this therapy before implantation.

METHODS

This current Polyanalgesic Consensus Conference (PACC) update was designed to address the deficiencies and emerging innovations since the previous PACC convened in 2012. A literature search identified publications available since the previous PACC publications in 2014, and relevant sources were contributed by the PACC members. After reviewing the literature, the panel determined the evidence levels and degrees of recommendations. The developed consensus was ranked as strong (>80%), moderate (50-79%), or weak (<49%).

RESULTS

The trialing for IT drug delivery systems (IDDS) remains an area of continued controversy. The PACC recommendations for trialing are presented in 34 consensus points and cover trialing for morphine, ziconotide, and medication admixtures; starting doses and titration practices; measurements of success; trial settings and monitoring; management of systemic opioids during trialing; and the role of psychological evaluation. Finally, the PACC describes clinical scenarios in which IT trialing is required or not required.

CONCLUSION

The PACC provides consensus guidance on best practices of trialing for IDDS implants. In addition, the PACC recommends that no trial may be required in certain patient populations.

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.

Multimodal intrathecal analgesia in refractory cancer pain

Background and aims

Cancer pain treatment has improved over the last decades. The majority of this population can be treated effectively with analgesics following the Guidelines of the original World Health Organisation (WHO). Unfortunately 10–15% of these patients still suffer from severe and refractory cancer pain, especially in the terminal phases of disease and require additional pain management modalities. Therefore, end-stage clinical interventions are particularly needed to minimize the perception of pain. With intrathecal therapy (ITT), drugs are delivered close to their site of action in the central nervous system avoiding first-pass metabolism and blood–brain barrier. It may improve analgesia with a smaller dose and possibly achieve a reduction in systemic or cerebral side effects compared to oral supplied medication alone. Multimodal analgesia enables further dose reduction with improved analgesia and fewer side effects.

Methods

In this retrospective research we investigated the effectiveness and side-effect profile of intrathecal morphine, bupivacaine and clonidine. Patients were followed until death occurred. Pain scores and side effects were recorded before initiating ITT (T0), just after initiating ITT (T1), at hospital discharge (T2), in the ambulant setting (T3) and the last obtained scores before death occurred (T4).

Results

Nine patients were included who suffered from severe and refractory cancer pain, not reacting to conventional pain management or had intolerable side effects. Primary tumour location was pancreatic (4), urothelial (3) and prostate (2). Primary pain was considered neuropathic or mixed neuropathic-nociceptive. The treatment team consisted of an anaesthetist, specialized nurse in coordination with primary physician, treating oncologist and specialized home care.

All patients were free of pain after initiation of the intrathecal therapy. The average follow-up period was 11 weeks in which there was a slight increase in NRS-score. In the last days before death occurred, half the patients were still free of pain. There were no problems during insertion of the catheter, device malfunction or infection. No severe adverse events defined as hypotension requiring inotropes, respiratory depression or neurological deficits were observed. Three patients experienced mild hypotension which gradually decreased after clonidine dose adjustment. Lower extremity weakness occurred in three patients as well. After bupivacaine dose adjustment the weakness disappeared in two patients and in one patient the lower extremity weakness persisted as a result of conus compression by tumour.

Conclusion and implications

Multimodal IT treatment with morphine, bupivacaine and clonidine is effective and safe for treating refractory cancer pain in the terminal phase of disease.

The study offers an important contribution to literature where there is still lack of convincing evidence about the benefits and harms of this type of pain management in patients with otherwise refractory cancer pain.

Antinociceptive Effects of AGAP, a Recombinant Neurotoxic Polypeptide: Possible Involvement of the Tetrodotoxin-Resistant Sodium Channels in Small Dorsal Root Ganglia Neurons

Antitumor-analgesic peptide (AGAP) is a novel recombinant polypeptide. The primary study showed that AGAP 1.0 mg/kg exhibited strong analgesic and antitumor effects. The tail vein administration of AGAP potently reduced pain behaviors in mice induced by intraplantar injection of formalin or intraperitoneal injection of acetic acid, without affecting basal pain perception. To further assess the mechanisms of AGAP, the effects of AGAP on sodium channels were assessed using the whole-cell patch clamp recordings in dorsal root ganglia (DRG) neurons. The results showed that AGAP (3–1000 nM) inhibited the sodium currents in small-diameter DRG neurons in a dose-dependent manner. 1000 nM AGAP could inhibit the current density-voltage relationship curve of sodium channels in a voltage-dependent manner and negatively shift the activation curves. 1000 nM AGAP could reduce the tetrodotoxin-resistant (TTX-R) sodium currents by 42.8% in small-diameter DRG neurons. Further analysis revealed that AGAP potently inhibited Na_V1.8 currents by 59.4%, and negatively shifted the activation and inactivation kinetics. 1000 nM AGAP also reduced the Na_V1.9 currents by 33.7%, but had no significant effect on activation and inactivation kinetics. Thus, our results demonstrated that submicromolar concentrations of AGAP inhibited TTX-R sodium channel in rat small-diameter DRG neurons. It is concluded that these new results may better explain, at least in part, the analgesic properties of this polypeptide.

Formulary Forum: Intrathecal Ziconotide for Refractory Chronic Pain

Objective:

TO describe the pharmacology, efficacy, and safety of ziconotide for treatment of severe chronic pain in patients who are candidates for intrathecal therapy.

Data Sources:

A PubMed/MEDLINE search (1966–June 2006) was conducted using the terms ziconotide, Priait, and SNX-111. Manufacturer-provided data, the Food and Drug Administration medical review of ziconotide, and abstracts presented at American Pain Society meetings (2001–2006) were also reviewed.

Study Selection and Data Extraction:

Human studies evaluating the efficacy and safety of ziconotide for the treatment of chronic pain were considered. Animal data were excluded.

Data Synthesis:

Ziconotide is the first and only neuronal-type (N-type) calcium-channel blocker. Ziconotide must be administered intrathecally via continuous infusion. A programmable implanted variable-rate microinfusion device, or an external microinfusion device and catheter must be utilized. In double-blind, placebo-controlled studies, ziconotide significantly improved patient perception of pain from baseline to the end of the study periods, which ranged from 11 to 21 days. Patients enrolled in clinical trials were intolerant of or refractory to other treatment modalities. There have been no studies that directly compared ziconotide with other intrathecal or systemic analgesics. Key ziconotide-related adverse events are neuropsychiatrie, including depression, cognitive impairment, and hallucinations; depressed levels of consciousness; and elevation of creatine kinase levels. Ziconotide is also associated with a risk of meningitis due to possible contamination of the microinfusion device.

Conclusions:

Ziconotide is a therapeutic option for treatment of severe chronic pain in patients who have exhausted all other agents, including intrathecal morphine, and for whom the potential benefit outweighs the risks of serious neuropsychiatric adverse effects and of having an implanted device. Further studies are needed to determine the comparative efficacy of ziconotide and other pain therapies.

Block of voltage-gated calcium channels by peptide toxins

Venoms from various predatory species, such as fish hunting molluscs scorpions, snakes and arachnids contain a large spectrum of toxins that include blockers of voltage-gated calcium channels. These peptide blockers act by two principal manners - physical occlusion of the pore and prevention of activation gating. Many of the calcium channel-blocking peptides have evolved to tightly occupy their binding pocket on the principal pore forming subunit of the channel, often rendering block poorly reversible. Moreover, several of the best characterized blocking peptides have developed a high degree of channel subtype selectivity. Here we give an overview of different types of calcium channel-blocking toxins, their mechanism of action, channel subtype specificity, and potential use as therapeutic agents. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

Ziconotide: Can we use it in palliative care?

Ziconotide (PRIALT ® ) is a new nonopioid treatment for chronic pain. It is a peptide that is the synthetic analog of the omega-conotoxin, derived from the marine snail, Conus magus. The therapeutic benefit of ziconotide derives from its potent and selective blockade of neuronal N-type voltage-sensitive calcium channels. Interference with these channels inhibits input from pain-sensing primary nociceptors. A recent clinical trial demonstrated that ziconotide has a significant analgesic effect compared to placebo in patients considered intolerant or refractory to other treatment such as systemic analgesics, adjunctive therapies, or intrathecal (IT) morphine. Thus, ziconotide is the first of a new class of agents—N-type calcium channel blockers, or NCCBs. Ziconotide may represent another option for patients with refractory pain.

Calcium Channel CaVα₁ Splice Isoforms - Tissue Specificity and Drug Action

Voltage-gated calcium ion channels are essential for numerous biological functions of excitable cells and there is wide spread appreciation of their importance as drug targets in the treatment of many disorders including those of cardiovascular and nervous systems. Each Cacna1 gene has the potential to generate a number of structurally, functionally, and in some cases pharmacologically unique CaVα1 subunits through alternative pre-mRNA splicing and the use of alternate promoters. Analyses of rapidly emerging deep sequencing data for a range of human tissue transcriptomes contain information to quantify tissue-specific and alternative exon usage patterns for Cacna1 genes. Cellspecific actions of nuclear DNA and RNA binding proteins control the use of alternate promoters and the selection of alternate exons during pre-mRNA splicing, and they determine the spectrum of protein isoforms expressed within different types of cells. Amino acid compositions within discrete protein domains can differ substantially among CaV isoforms expressed in different tissues, and such differences may be greater than those that exist across CaV channel homologs of closely related species. Here we highlight examples of CaV isoforms that have unique expression patterns and that exhibit different pharmacological sensitivities. Knowledge of expression patterns of CaV isoforms in different human tissues, cell populations, ages, and disease states should inform strategies aimed at developing the next generation of CaV channel inhibitors and agonists with improved tissue-specificity.

Efficacy of (S)-Lacosamide in preclinical models of cephalic pain

Migraine is one of the world's most common neurological disorders. Current acute migraine treatments have suboptimal efficacy, and new therapeutic options are needed. Approaches targeting calcitonin gene related peptide (CGRP) signaling are clinically effective, but small molecule antagonists have not been advanced because of toxicity. In this study, we explored the axonal growth/specification collapsin response mediator protein 2 (CRMP2) as a novel “druggable” target for inhibiting CGRP release and for potential relevance for treatment of migraine pain. Collapsin response mediator protein 2 has been demonstrated to regulate N-type voltage-gated Ca²⁺ channel activity and Ca²⁺-dependent CGRP release in sensory neurons. The coexpression of CRMP2 with N-type voltage-gated Ca²⁺ channel and CGRP in trigeminal ganglia (TGs) sensory neurons suggested the possibility of a novel approach to regulate CGRP release in the trigeminal system. Screening protocols surprisingly revealed that (S)-lacosamide ((S)-LCM), an inactive analog of the clinically approved small molecule antiepileptic drug (R)-lacosamide (Vimpat), inhibited CRMP2 phosphorylation by cyclin-dependent kinase 5 in rat TG slices and decreased depolarization-evoked Ca²⁺ influx in TG cells in culture. (S)-LCM significantly blocked capsaicin-evoked CGRP release from dural nerve terminals in the rat in ex vivo cranial cup preparation. Additionally, cephalic and extracephalic cutaneous allodynia induced in rats by activation of dural nociceptors with a cocktail of inflammatory mediators, was inhibited by oral administration of (S)-LCM. The confirmation of CRMP2 as an upstream mediator of CGRP release, together with the brain penetrance of this molecule suggests (S)-LCM as a potential therapy for acute migraine.

Intrathecal Therapy for Cancer-Related Pain

Objective. The increasing incidence of cancer survivorship has shifted treatment of cancer-related pain from short-term analgesia to long-term chronic pain management. As a result, alternatives to oral analgesics, such as intrathecal therapy, may be beneficial for patients with cancer-related pain. The authors review the use of intrathecal therapy in the management of cancer-related pain.

Methods. The Medline database was searched for English-language articles that included “ziconotide” or “morphine” AND (“cancer” OR “malignant”) AND “intrathecal” in title or abstract. Available abstracts from scientific congresses in the areas of neuromodulation and oncology were also reviewed.

Results. Intrathecal therapy provides pain relief with reduced systemic concerns in patients with cancer-related pain. Patients should undergo multidisciplinary evaluation and, in most cases, drug trialing before intrathecal pump implantation. Morphine, an opioid (µ-opioid receptor antagonist), and ziconotide, a nonopioid (selective N-type calcium channel inhibitor), are both approved for intrathecal analgesia; however, tolerance and safety concerns may deter the use of intrathecal morphine. Ziconotide has also shown efficacy for reduction of cancer-related pain; however, proper dosing and titration must be used to prevent adverse events. There is little information available on use of intrathecal therapies specifically in cancer survivors.

Conclusions. Treatment of cancer-related pain has shifted toward chronic pain management strategies, especially among cancer survivors. Intrathecal therapy provides an alternate route of administration of chronic pain medications (e.g., morphine and ziconotide) for cancer patients with and without active disease, although additional research is needed to support effectiveness in cancer survivors.

Emerging targets in treating pain

PURPOSE OF REVIEW

To provide an overview on drug targets and emerging pharmacological treatment options for chronic pain.

RECENT FINDINGS

Chronic pain poses an enormous socioeconomic burden for the more than 30% of people who suffer from it, costing over $600 billion per year in the USA. In recent years, there has been a surge in preclinical and clinical research endeavors to try to stem this epidemic. Preclinical studies have identified a wide array of potential targets, with some of the most promising translational research being performed on novel opioid receptors, cannabinoid receptors, selective ion channel blockers, cytokine inhibitors, nerve growth factor inhibitors, N-methyl-D-aspartate receptor antagonists, glial cell inhibitors, and bisphosphonates.

SUMMARY

There are many obstacles for the development of effective medications to treat chronic pain, including the inherent challenges in identifying pathophysiological mechanisms, the overlap and multiplicity of pain pathways, and off-target adverse effects stemming from the ubiquity of drug target receptor sites and the lack of highly selective receptor ligands. Despite these barriers, the number and diversity of potential therapies have continued to grow, to include disease-modifying and individualized drug treatments.

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.

Antinociceptive effect of a novel armed spider peptide Tx3-5 in pathological pain models in mice

The venom of the Brazilian armed spider Phoneutria nigriventer is a rich source of biologically active peptides that have potential as analgesic drugs. In this study, we investigated the analgesic and adverse effects of peptide 3-5 (Tx3-5), purified from P. nigriventer venom, in several mouse models of pain. Tx3-5 was administered by intrathecal injection to mice selected as models of postoperative (plantar incision), neuropathic (partial sciatic nerve ligation) and cancer-related pain (inoculation with melanoma cells) in animals that were either sensitive or tolerant to morphine. Intrathecal administration of Tx3-5 (3-300 fmol/site) in mice could either prevent or reverse postoperative nociception, with a 50 % inhibitory dose (ID50) of 16.6 (3.2-87.2) fmol/site and a maximum inhibition of 87 ± 10 % at a dose of 30 fmol/site. Its effect was prevented by the selective activator of L-type calcium channel Bay-K8644 (10 μg/site). Tx3-5 (30 fmol/site) also produced a partial antinociceptive effect in a neuropathic pain model (inhibition of 67 ± 10 %). Additionally, treatment with Tx3-5 (30 fmol/site) nearly abolished cancer-related nociception with similar efficacy in both morphine-sensitive and morphine-tolerant mice (96 ± 7 and 100 % inhibition, respectively). Notably, Tx3-5 did not produce visible adverse effects at doses that produced antinociception and presented a TD50 of 1125 (893-1418) fmol/site. Finally, Tx3-5 did not alter the normal mechanical or thermal sensitivity of the animals or cause immunogenicity. Our results suggest that Tx3-5 is a strong drug candidate for the treatment of painful conditions.

Intrathecal Ziconotide: Dosing and Administration Strategies in Patients With Refractory Chronic Pain

Introduction

Ziconotide is a non‐opioid analgesic for intrathecal (IT) administration. The aim of this review is to provide a comprehensive and clinically relevant summary of the literature on dosing and administration with IT ziconotide in the management of refractory chronic pain, and to describe novel dosing strategies intended to improve clinical outcomes.

Materials and Methods

A Medline search was conducted for “ziconotide,” supplemented by manual searching of published bibliographies and abstracts from conferences.

Results

Early experience with IT ziconotide in clinical trials combined with improved understanding of drug pharmacokinetics in the cerebrospinal fluid have led to a reappraisal of approaches to trialing and initiation of continuous‐infusion therapy in an effort to improve tolerability. The traditional paradigm of trialing by inpatient continuous infusion may be shifting toward outpatient trialing by IT bolus, although definitions of success and specific protocols remain to be agreed upon. Expert consensus on IT continuous infusion with ziconotide suggests a starting dose of 0.5 to 1.2 mcg/day followed by dose titration of ≤0.5 mcg/day on a no more than weekly basis, according to individual patients’ pain reductions and regimen tolerability.

Discussion

Newer modalities that include patient‐controlled analgesia and nocturnal flex dosing have been shown to hold promise of further improvements in ziconotide efficacy and tolerability.

Conclusions

Clinical trials and experience confirm the feasibility and usefulness of IT ziconotide in the management of refractory chronic pain. Emerging evidence suggests that additional IT delivery options may further expand the usefulness and benefits of ziconotide.

Health Services Utilization and Payments in Patients With Cancer Pain: A Comparison of Intrathecal Drug Delivery vs. Conventional Medical Management

Introduction

To compare health services utilization and payments for cancer patients who received an implantable intrathecal drug delivery (IDD) system, consisting of a pump and catheter, vs. conventional medical management (CMM) for the treatment of cancer‐related pain.

Methods

This retrospective claims‐data analysis compared health services utilization and payments in a population of patients receiving either IDD or CMM for treatment of cancer pain. Patients were propensity score‐matched 1:1 based on characteristics including, but not limited to, age, gender, cancer type, comorbid conditions, and health care utilization and payments.

Results

From a sample of 142 IDD patients and 3188 CMM patients who met all inclusion/exclusion criteria, 73 matched pairs were obtained. In the year following implant, IDD patients had a consistent trend of lower medical utilization, and total payments that were $3195 lower compared to CMM.

Conclusions

Despite the high initial cost of IDD, this analysis suggests that patients with IDD incur lower medical utilization and payments over the first year post‐implant. Further analysis comprised of a larger, longitudinal sample would contribute to health economics and outcomes research, and assist with future practice guideline development.

Anti-hepatoma activity of the stiff branched β-d-glucan and effects of molecular weight

The water soluble β-d-glucan AF1 with short branches isolated from Auricularia auricula-judae exhibited significant anti-hepatoma activities, and it was confirmed that AF1 had stiff chains and could induce cancer cell apoptosis and anti-angiogenesis through activating immune responses.

An Overview of Pharmacologic Management of Chronic Pain

Patients with chronic pain can be challenging to manage and historically providers have relied on opiates to treat pain. Recent studies have brought into question the safety and efficacy of chronic opiate therapy in the noncancer population. There is a vast amount of literature to support the use of nonsteroidal anti-inflammatory medications, antidepressants, anticonvulsants, topical agents, cannabinoids, and botulinum toxin either in conjunction with or in lieu of opioids. Intrathecal drug delivery systems can deliver some of these medications directly to their primary site of action while minimizing the side effects seen with systemic administration.

Managing Neuropathic Pain

Neuropathic pain (NP) arises from injuries or diseases affecting the somatosensory component of the nervous system at any level of the peripheral or central nervous system. NP is diagnosed based on common neurologic signs and symptoms. NP is best treated with a combination of multiple therapeutic approaches, and treatments include conservative, complementary, medical, interventional, and surgical treatment modalities. Goals of treatment are the same as in pain management and include improvement in pain control and in coping skills as well as restoration of functional status. Most patients with NP benefit most from an individualized, multimodal approach that emphasizes both pain and function.

Delivery of ziconotide to cerebrospinal fluid via intranasal pathway for the treatment of chronic pain

The purpose of the current study was to investigate the plausibility of delivery of ziconotide to the cerebrospinal fluid (CSF) via intranasal administration. Ziconotide was administered either in the form of solution or Kolliphor P 407 gels (KP 407) intranasally in Sprague-Dawley rats. The effect of incorporation of chitosan in the formulation was also investigated. Time course of drug in the CSF was investigated by collecting CSF from cisterna magna. Pharmacokinetics of ziconotide in CSF following intrathecal and intravenous (i.v.) administration of ziconotide was investigated. Upon intrathecal administration the elimination rate constant of ziconotide in CSF was found to be 1.01±0.34h(-1). The Cmax and Tmax of ziconotide in CSF following intravenous administration were found to be 37.78±6.8ng/mL and ~2h respectively. The time required to attain maximum concentration (Tmax) in CSF was less upon intranasal administration (15min) compared to i.v. administration (120min). Presence of chitosan enhanced the overall bioavailability of ziconotide from intranasal solution and gel formulations. The elimination rate constant of ziconotide in CSF following intranasal and intravenous administration of ziconotide solution was found to be 0.54±0.08h(-1) and 0.42±0.10h(-1) respectively. Whereas, intranasal administration of ziconotide in the form of in situ forming gel lowered the elimination rate significantly. These results suggest that intranasal administration could be a potential noninvasive and patient compliant method of delivering ziconotide to CSF to treat chronic pain.

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.

The Physiology, Pathology, and Pharmacology of Voltage-Gated Calcium Channels and Their Future Therapeutic Potential

Voltage-gated calcium channels are required for many key functions in the body. In this review, the different subtypes of voltage-gated calcium channels are described and their physiologic roles and pharmacology are outlined. We describe the current uses of drugs interacting with the different calcium channel subtypes and subunits, as well as specific areas in which there is strong potential for future drug development. Current therapeutic agents include drugs targeting L-type Ca(V)1.2 calcium channels, particularly 1,4-dihydropyridines, which are widely used in the treatment of hypertension. T-type (Ca(V)3) channels are a target of ethosuximide, widely used in absence epilepsy. The auxiliary subunit α2δ-1 is the therapeutic target of the gabapentinoid drugs, which are of value in certain epilepsies and chronic neuropathic pain. The limited use of intrathecal ziconotide, a peptide blocker of N-type (Ca(V)2.2) calcium channels, as a treatment of intractable pain, gives an indication that these channels represent excellent drug targets for various pain conditions. We describe how selectivity for different subtypes of calcium channels (e.g., Ca(V)1.2 and Ca(V)1.3 L-type channels) may be achieved in the future by exploiting differences between channel isoforms in terms of sequence and biophysical properties, variation in splicing in different target tissues, and differences in the properties of the target tissues themselves in terms of membrane potential or firing frequency. Thus, use-dependent blockers of the different isoforms could selectively block calcium channels in particular pathologies, such as nociceptive neurons in pain states or in epileptic brain circuits. Of important future potential are selective Ca(V)1.3 blockers for neuropsychiatric diseases, neuroprotection in Parkinson's disease, and resistant hypertension. In addition, selective or nonselective T-type channel blockers are considered potential therapeutic targets in epilepsy, pain, obesity, sleep, and anxiety. Use-dependent N-type calcium channel blockers are likely to be of therapeutic use in chronic pain conditions. Thus, more selective calcium channel blockers hold promise for therapeutic intervention.

The evidence of neuraxial administration of analgesics for cancer-related pain: a systematic review

BACKGROUND

The present systematic review analysed the existing evidence of analgesic efficacy and side effects of opioids without and with adjuvant analgesics delivered by neuraxial route (epidural and subarachnoid) in adult patients with cancer.

METHODS

Search strategy was elaborated with words related to cancer, pain, neuraxial route, analgesic and side effects. The search was performed in PubMed, EMBASE, and Cochrane for the period until February 2014. Studies were analysed according to methods, results, quality of evidence, and strength of recommendation.

RESULTS

The number of abstracts retrieved was 2147, and 84 articles were selected for full reading. The final selection comprised nine articles regarding randomised controlled trials (RCTs) divided in four groups: neuraxial combinations of opioid and adjuvant analgesic compared with neuraxial administration of opioid alone (n = 4); single neuraxial drug in bolus compared with continuous administration (n = 2); single neuraxial drug compared with neuraxial placebo (n = 1); and neuraxial opioid combined with or without adjuvant analgesic compared with other comprehensive medical management than neuraxial analgesics (n = 2). The RCTs presented clinical and methodological diversity that precluded a meta-analysis. They also presented several limitations, which reduced study internal validity. However, they demonstrated better pain control for all interventions analysed. Side effects were described, but there were few significant differences in favour of the tested interventions.

CONCLUSION

Heterogeneous characteristics and several methodological limitations of the studies resulted in evidence of low quality and a weak recommendation for neuraxial administration of opioids with or without adjuvant analgesics in adult patients with cancer.

Genetic disruption of voltage-gated calcium channels in psychiatric and neurological disorders

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Voltage-gated calcium channel classification—genes and proteins.

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Genetic analysis of neuropsychiatric syndromes.

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Calcium channel genes identified from GWA studies of psychiatric disorders.

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Rare mutations in calcium channel genes in psychiatric disorders.

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Pathophysiological sequelae of CACNA1C mutations and polymorphisms.

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Monogenic disorders resulting from harmful mutations in other voltage-gated calcium channel genes.

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Changes in calcium channel gene expression in disease.

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Involvement of voltage-gated calcium channels in early brain development.

This review summarises genetic studies in which calcium channel genes have been connected to the spectrum of neuropsychiatric syndromes, from bipolar disorder and schizophrenia to autism spectrum disorders and intellectual impairment. Among many other genes, striking numbers of the calcium channel gene superfamily have been implicated in the aetiology of these diseases by various DNA analysis techniques. We will discuss how these relate to the known monogenic disorders associated with point mutations in calcium channels. We will then examine the functional evidence for a causative link between these mutations or single nucleotide polymorphisms and the disease processes. A major challenge for the future will be to translate the expanding psychiatric genetic findings into altered physiological function, involvement in the wider pathology of the diseases, and what potential that provides for personalised and stratified treatment options for patients.

Resolution of chronic migraine headaches with intrathecal ziconotide: a case report

Background

Migraine headaches are a common and functionally debilitating disorder affecting approximately 17% of women and 5.6% of men. Compared to episodic migraine patients, chronic migraineurs are more likely to be occupationally disabled, miss family activities, have comorbid anxiety and/or chronic pain disorders, and utilize significantly more health care dollars. Ziconotide is a calcium channel blocker used for the treatment of chronic severe pain without issues of tolerance or dependency found with opioid therapy.

Case

A 59-year-old female had an intrathecal baclofen pump placed for spasticity secondary to multiple sclerosis. Her symptoms also included lower extremity neuropathic pain and severe migraine headaches with 22 migraine headache days per month. Prior treatments included non-steroidal anti-inflammatory drugs, triptans, anticonvulsants, antihypertensives, and Botox injections which reduced her symptoms to four migraine days per month at best. While her spasticity had markedly improved with intrathecal baclofen, ziconotide was added to help her neuropathic pain complaints. Following initiation of low-dose ziconotide (1 µg/day), the patient noted both lower extremity pain improvement and complete resolution of migraine headaches resulting in zero migraine days per month. She has now been migraine free for 8 months.

Conclusion

Upon review of the available literature, there are no published cases of migraine improvement with intrathecal ziconotide. This represents the first case describing resolution of migraine symptoms with low-dose ziconotide.