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

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.

Initiation of Intrathecal Drug Delivery Dramatically Reduces Systemic Opioid Use in Patients With Advanced Cancer

OBJECTIVES

Pain is common in cancer, affecting more than 70% of patients with advanced disease. Intrathecal drug delivery systems (IDDS) are a well-established treatment for patients with refractory cancer pain, improving pain control and reducing associated side effects. To date, details of systemic opioid use before and after IDDS implant have not been reported.

MATERIALS AND METHODS

We conducted a retrospective review of patients at Huntsman Cancer Institute-University of Utah treated with IDDS for cancer pain from May 2014 to May 2018. Oral, transdermal, and parenteral opioid use before IDDS implant was compared to use 30 days postoperatively.

RESULTS

A total of 173 patients were included, 93% with stage IV disease. The pre-implant median daily oral morphine equivalent (OME) was 240 mg (interquartile range 130-390, range 0-2616 mg). OME doses >200 mg/day were required by 57% of patients, and >500 mg OME by 19% of patients. The post-implant median OME was 0 mg (interquartile range 0-0, range 0-480 mg) and 82.6% of patients discontinued systemic opioids completely. 11.0% of patients used <100 mg OME, and only 1.7% of patients used >200 mg OME. Mean OME decreased by 94% following IDDS implant (p < 0.0001) and all patients who continued to use systemic opioids required a lower OME compared to pre-implant.

CONCLUSIONS

In the largest cohort of patients with advanced cancer and refractory pain treated with IDDS, implantation was associated with a dramatic reduction in systemic opioid use 30 days postoperatively, with a large majority of patients discontinuing systemic opioids. Those patients that continued systemic opioids utilized significantly lower doses as compared to their pre-implant dose.

Intrathecal Drug Delivery Systems for Cancer Pain: An Analysis of a Prospective, Multicenter Product Surveillance Registry

BACKGROUND

The safety and efficacy of intrathecal drug delivery systems (IDDSs) for the treatment of cancer-related pain have been demonstrated in randomized controlled clinical trials (RCTs). Despite positive evidence for this therapy, IDDS remains underutilized to treat cancer pain. Real-world registry data augment existing safety and effectiveness data and are presented here to broaden awareness of this therapeutic option, needed for adequate cancer-related pain treatment, and as a viable tool addressing concerns with systemic opioid use.

METHODS

This prospective, long-term, multicenter (United States, Western Europe, and Latin America) registry started in 2003 to monitor the performance of SynchroMed Infusion Systems. Patient-reported outcomes were added in 2013. Before data acquisition, all sites obtained Ethics Committee/Institutional Review Board approval and written patient consent. The study was registered (NCT01524276 at clinicaltrials.gov) before patients were enrolled. Patients who provided informed consent were enrolled in the registry at initial IDDS implant or replacement.

RESULTS

Through July 2017, 1403 patients with cancer pain were enrolled and implanted. The average (minimum/maximum) age of patients was 59 years (13/93 years), with 56.6% female. The most frequent cancer types were lung, breast, colon/rectal, pancreatic, and prostate. The majority of patients whose registry follow-up ended (87%; 1141/1311) were followed through death, with 4.3% (n = 57) exiting due to device explant or therapy discontinuation; the remaining 113 (8.6%) discontinued for reasons such as transfer of care, lost to follow-up, and site closure. Pain scores within the cohort of patients providing baseline and follow-up data improved significantly at 6 (P = .0007; n = 103) and 12 (P = .0026; n = 55) months compared to baseline, with EuroQol with 5 dimensions (EuroQol-5D) scores showing significant improvement at 6 months (P = .0016; n = 41). Infection requiring surgical intervention (IDDS explant, replacement, pocket revision, irrigation and debridement, etc) was reported in 3.2% of patients.

CONCLUSIONS

Adequate and improved pain control in patients with cancer, even in advanced stages, with concurrent quality of life maintenance is attainable. Results from this large-scale, multicenter, single-group cohort supplement existing RCT data that support IDDS as a safe and effective therapeutic option with a positive benefit-risk ratio in the treatment of cancer pain.

Analgesic and side effects of intravenous recombinant Phα1β

Background

Intrathecal injection of voltage-sensitive calcium channel blocker peptide toxins exerts analgesic effect in several animal models of pain. Upon intrathecal administration, recombinant Phα1β exerts the same analgesic effects as the those of the native toxin. However, from a clinical perspective, the intrathecal administration limits the use of anesthetic drugs in patients. Therefore, this study aimed to investigate the possible antinociceptive effect of intravenous recombinant Phα1β in rat models of neuropathic pain, as well as its side effects on motor, cardiac (heart rate and blood pressure), and biochemical parameters.

Methods

Male Wistar rats and male Balb-C mice were used in this study. Giotto Biotech® synthesized the recombinant version of Phα1β using Escherichia coli expression. In rats, neuropathic pain was induced by chronic constriction of the sciatic nerve and paclitaxel-induced acute and chronic pain. Mechanical sensitivity was evaluated using von Frey filaments. A radiotelemeter transmitter (TA11PA-C10; Data Sciences, St. Paul, MN, USA) was placed on the left carotid of mice for investigation of cardiovascular side effects. Locomotor activity data were evaluated using the open-field paradigm, and serum CKMB, TGO, TGP, LDH, lactate, creatinine, and urea levels were examined.

Results

Intravenous administration of recombinant Phα1β toxin induced analgesia for up to 4 h, with ED₅₀ of 0.02 (0.01-0.03) mg/kg, and reached the maximal effect (E_max = 100% antinociception) at a dose of 0.2 mg/kg. No significant changes were observed in any of the evaluated motor, cardiac or biochemical parameters.

Conclusion

Our data suggest that intravenous administration of recombinant Phα1β may be feasible for drug-induced analgesia, without causing any severe side effects.

Indian Society for Study of Pain, Cancer Pain Special Interest Group Guidelines on Interventional Management for Cancer Pain

The Indian Society for Study of Pain (ISSP), Cancer Pain Special Interest Group guidelines on interventional management for cancer pain in adults provide a structured, stepwise approach which will help to improve the management of cancer pain and to provide the patients with minimally acceptable quality of life. The guidelines have been developed based on the available literature and evidence, to suit the needs, patient population, and situations in India. A questionnaire based on the key elements of each sub draft addressing certain inconclusive areas where evidence was lacking was made available on the ISSP website and circulated by e-mail to all the ISSP and Indian Association of Palliative Care members. We recommend using interventional management when conventional therapy fails to offer adequate benefits or causes undesirable side effects. Vertebroplasty should be offered to patients with uncontrolled bone pain when expertise is available.

Cacna1b alternative splicing impacts excitatory neurotransmission and is linked to behavioral responses to aversive stimuli

Presynaptic CaV2.2 channels control calcium entry that triggers neurotransmitter release at both central and peripheral synapses. The Cacna1b gene encodes the α1-pore forming subunit of CaV2.2 channels. Distinct subsets of splice variants of CaV2.2 derived from cell-specific alternative splicing of the Cacna1b pre-mRNA are expressed in specific subpopulations of neurons. Four cell-specific sites of alternative splicing in Cacna1b that alter CaV2.2 channel function have been described in detail: three cassette exons (e18a, e24a, and e31a) and a pair of mutually exclusive exons (e37a/e37b). Cacna1b mRNAs containing e37a are highly enriched in a subpopulation of nociceptors where they influence nociception and morphine analgesia. E37a-Cacna1b mRNAs are also expressed in brain, but their cell-specific expression in this part of the nervous system, their functional consequences in central synapses and their role on complex behavior have not been studied. In this report, we show that e37a-Cacna1b mRNAs are expressed in excitatory projection neurons where CaV2.2 channels are known to influence transmitter release at excitatory inputs from entorhinal cortex (EC) to dentate gyrus (DG). By comparing behaviors of WT mice to those that only express e37b-CaV2.2 channels, we found evidence that e37a-CaV2.2 enhances behavioral responses to aversive stimuli. Our results suggest that alternative splicing of Cacna1b e37a influences excitatory transmitter release and couples to complex behaviors.

Cancer- and Non-cancer Related Chronic Pain: From the Physiopathological Basics to Management

The prevalence of chronic pain is between 33% to 64% and is due to cancer pain, but it has also been observed in non-cancer patients. Chronic pain is associated with lower quality of life and higher psychological distress and depressive/anxiety disorders in patients without a history of disorder. In this study we evaluated in clinical practice the effectiveness of the intrathecal pump in 140 patients who underwent pain therapy at our Center. These patients were consecutively enrolled from January 2010 to July 2018. Follow-up was carried out over these eight years regarding the infusion modalities. Pain relief was obtained in 71 (50,7%) patients out of the 140 that experienced satisfactory pain control globally. Intrathecal therapy is one of the best options for chronic severe refractory pain. The greatest advantage of this therapy is due to the possibility of treating the pain with minimal dosages of the drug, avoiding the appearance of troublesome side effects.

Inflammation Induced Sensory Nerve Growth and Pain Hypersensitivity Requires the N-Type Calcium Channel Cav2.2

Voltage-gated calcium channels (VGCCs) are important mediators of pain hypersensitivity during inflammatory states, but their role in sensory nerve growth remains underexplored. Here, we assess the role of the N-type calcium channel Cav2.2 in the complete Freund’s adjuvant (CFA) model of inflammatory pain. We demonstrate with in situ hybridization and immunoblotting, an increase in Cav2.2 expression after hind paw CFA injection in sensory neurons that respond to thermal stimuli, but not in two different mechanosensitive neuronal populations. Further, Cav2.2 upregulation post-CFA correlates with thermal but not mechanical hyperalgesia in behaving mice, and this hypersensitivity is blocked with a specific Cav2.2 inhibitor. Voltage clamp recordings reveal a significant increase in Cav2.2 currents post-CFA, while current clamp analyses demonstrate a significant increase in action potential frequency. Moreover, CFA-induced sensory nerve growth, which involves the extracellular signal-related kinase (ERK1/2) signaling pathway and likely contributes to inflammation-induced hyperalgesia, was blocked with the Cav2.2 inhibitor. Together, this work uncovers a role for Cav2.2 during inflammation, demonstrating that VGCC activity can promote thermal hyperalgesia through both changes in firing rates of sensory neurons as well as promotion of new neurite outgrowth.

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.

Intrathecal Drug Delivery Systems for Refractory Pancreatic Cancer Pain: Observational Follow-up Study Over an 11-Year Period in a Comprehensive Cancer Center

BACKGROUND

Pancreatic cancer is the fourth leading cause of cancer-related death in Europe and the United States. Studies have demonstrated that patients with pancreatic cancer have a high prevalence of pain, with rates varying from 47% to 82%. Analgesia using intrathecal drug delivery systems (IDDS) has been poorly studied specifically in this population.

METHODS

The IDDS for pancreatic cancer pain was a follow-up observational study designed to evaluate 11-year results of IDDS for refractory pancreatic cancer pain at the Institut de Cancérologie de L'Ouest, Paul Papin in France. Patients were followed from March 2006 to April 2017. Patients were selected for IDDS based on multidisciplinary meeting discussion. All IDDS-treated patients were prescribed a combined intrathecal analgesics regimen through a catheter placed according to painful metameric level. Postimplant assessment of pain was determined using a numerical rating scale (NRS). Patients were followed via day-hospital visits and telephone calls at least monthly until death. Pain scores were compared using the Wilcoxon signed rank test. Overall survival (OS) was estimated using the Kaplan-Meier method and compared between groups by log rank tests.

RESULTS

Ninety-three patients received IDDS, and total therapy duration accounts for 10,300 IDDS days. Implanted patients suffered from severe pain before implantation (median presurgical NRS, 8 [interquartile range, 7-9]) despite a median 360 mg (260-600) oral morphine equivalent daily dose. Median OS in the whole cohort after intrathecal treatment start was 82 days (95% confidence interval, 59-95). Median OS after surgery for implantable pump was 91 days (83-111) and for external pump 27 days (20-49; P < .0001). IDDS was associated with pain relief with a significant statistical difference between preimplantation NRS pain score and 1 week (median, -6 [-7 to -4]; P < .001), 1 month (median, -5 [-6 to -3]; P < .001), and 3 months (median, -6 [-7 to -4]; P < .001). Severe pain (NRS score, ≥7) decreased from 89.2% before surgery to 4.5% after 1 week, 6.7% after 1 month, and 10.3% after 3 months of IDDS implant (P < .01). Global complications rate was low, consistent with published literature.

CONCLUSIONS

Despite our study's limitations, results suggest that long-term IDDS for refractory malignant pain due to pancreatic cancer was both efficacious and safe in pancreatic cancer pain. We have demonstrated, in the largest series of IDDS for pancreatic cancer pain reported yet, a clinically and statistically significant pain reduction in patients receiving IDDS.

Reviewing without a Clinical Background Is Detrimental for Cancer Pain Management

Reviews are a fundamental space for summarizing and spreading knowledge on a particular topic. Methodologic skills may improve the clarity and the meaning of data presentation. A recent editorial choice provided an advanced update on a topic such as cancer pain, providing meaningful and appropriate information on hot topics of cancer pain management. Recent reviews have reported strange and misleading data, suggesting to some adjuvant drugs or opioids for mild-moderate pain instead of opioids on the basis of an incomprehensible analysis performed without any clinical sense. This is a serious problem because such information, published in an authoritative journal, could dis-educate oncologists in their daily practice.

Phα1β Spider Toxin Reverses Glial Structural Plasticity Upon Peripheral Inflammation

The incoming signals from injured sensory neurons upon peripheral inflammation are processed in the dorsal horn of spinal cord, where glial cells accumulate and play a critical role in initiating allodynia (increased pain in response to light-touch). However, how painful stimuli in the periphery engage glial reactivity in the spinal cord remains unclear. Here, we found that a hind paw inflammation induced by CFA produces robust morphological changes in spinal astrocytes and microglia compatible with the reactive phenotype. Strikingly, we discovered that a single intrathecal injection with venom peptides that inhibit calcium channels reversed all the glial pathological features of the peripheral inflammation. These effects were more apparent in rats treated with the Phα1β spider toxin (non-specific calcium channel antagonist) than ω-MVIIA cone snail toxin (selective N-type calcium channel antagonist). These data reveal for the first time a venom peptide acting on glial structural remodeling in vivo. We, therefore, suggest that calcium-dependent plasticity is an essential trigger for glial cells to initiate reactivity, which may represent a new target for the antinociceptive effects of Phα1β and ω-MVIIA toxins in inflammatory pain conditions.

Managing Chronic Non-Malignant Pain in the Elderly: Intrathecal Therapy

Intrathecal drug delivery (IDD) was first described in 1981 by Onofrio, who used a pump for continuous and intrathecal delivery of morphine to treat cancer pain. Over the following four decades, many reports supported this treatment method with implanted pumps for cancer and non-cancer pain. To date, more than 300,000 pumps for pain therapy and spasticity have been implanted worldwide. This article reviews current knowledge regarding intrathecal opioid therapy, focusing particularly on the use of IDD in elderly patients. Current literature is presented, and the arguments in favor of and against this therapy in elderly patients are discussed.

Spider venom peptides as potential drug candidates due to their anticancer and antinociceptive activities

Spider venoms are known to contain proteins and polypeptides that perform various functions including antimicrobial, neurotoxic, analgesic, cytotoxic, necrotic, and hemagglutinic activities. Currently, several classes of natural molecules from spider venoms are potential sources of chemotherapeutics against tumor cells. Some of the spider peptide toxins produce lethal effects on tumor cells by regulating the cell cycle, activating caspase pathway or inactivating mitochondria. Some of them also target the various types of ion channels (including voltage-gated calcium channels, voltage-gated sodium channels, and acid-sensing ion channels) among other pain-related targets. Herein we review the structure and pharmacology of spider-venom peptides that are being used as leads for the development of therapeutics against the pathophysiological conditions including cancer and pain.

Marine anticancer drugs and their relevant targets: a treasure from the ocean

Marine organisms comprising animals and plants are wealthiest sources of bioactive compounds possessing various pharmacological properties specifically: free radical scavenging, antitumor, antimicrobial, analgesic, neuroprotective and immunomodulatory. Marine drugs provide an alternative source to meet the demand of effective, safe and low-cost drugs that are rising with the continuously growing world population. Cancer is one of the leading reasons of mortality in western nations in contrast to communicable diseases of developing nations. In spite of outstanding developments in cancer therapy in past three decades, there is still an insistent necessity for innovative drugs in the area of cancer biology, especially in the unexplored area of marine anticancer compounds. However, recent technological innovations in structure revelation, synthetic creation of new compounds and biological assays have made possible the isolation and clinical assessment of innumerable unique anticancer compounds from marine environment. This review provides an insight into the anticancer research so far conducted in the area of the marine natural products/synthetic derivatives, their possible molecular targets and the current challenges in the drug development. Graphical abstract.

Dexmedetomidine enhances glymphatic brain delivery of intrathecally administered drugs

Drug delivery to the central nervous system remains a major problem due to biological barriers. The blood-brain-barrier can be bypassed by administering drugs intrathecally directly to the cerebrospinal fluid (CSF). The glymphatic system, a network of perivascular spaces promoting fluid exchange between CSF and interstitial space, could be utilized to enhance convective drug delivery from the CSF to the parenchyma. Glymphatic flow is highest during sleep and anesthesia regimens that induce a slow-wave sleep-like state. Here, using mass spectrometry and fluorescent imaging techniques, we show that the clinically used α₂-adrenergic agonist dexmedetomidine that enhances EEG slow-wave activity, increases brain and spinal cord drug exposure of intrathecally administered drugs in mice and rats. Using oxycodone, naloxone, and an IgG-sized antibody as relevant model drugs we demonstrate that modulation of glymphatic flow has a distinct impact on the distribution of intrathecally administered therapeutics. These findings can be exploited in the clinic to improve the efficacy and safety of intrathecally administered therapeutics.

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.

Ablation of α2δ-1 inhibits cell-surface trafficking of endogenous N-type calcium channels in the pain pathway in vivo

Neuronal N-type (Ca_V2.2) voltage-gated calcium channels are important at the first synapse in the pain pathway. In this study, we have characterized a knockin mouse containing Ca_V2.2 with an extracellular HA tag to determine the localization of Ca_V2.2 in primary afferent pain pathways. These endogenous channels have been visualized at the plasma membrane and rigorously quantified in vivo. We examined the effect of ablation of the calcium channel auxiliary subunit α₂δ-1 (the target of gabapentinoids) on Ca_V2.2 distribution. We found preferential cell-surface localization of Ca_V2.2 in DRG nociceptor neuron cell bodies was lost, accompanied by a dramatic reduction at dorsal horn terminals, but no effect on distribution of other spinal cord synaptic markers.

The auxiliary α₂δ calcium channel subunits play key roles in voltage-gated calcium channel function. Independent of this, α₂δ-1 has also been suggested to be important for synaptogenesis. Using an epitope-tagged knockin mouse strategy, we examined the effect of α₂δ-1 on Ca_V2.2 localization in the pain pathway in vivo, where Ca_V2.2 is important for nociceptive transmission and α₂δ-1 plays a critical role in neuropathic pain. We find Ca_V2.2 is preferentially expressed on the plasma membrane of calcitonin gene-related peptide-positive small nociceptors. This is paralleled by strong presynaptic expression of Ca_V2.2 in the superficial spinal cord dorsal horn. EM-immunogold localization shows Ca_V2.2 predominantly in active zones of glomerular primary afferent terminals. Genetic ablation of α₂δ-1 abolishes Ca_V2.2 cell-surface expression in dorsal root ganglion neurons and dramatically reduces dorsal horn expression. There was no effect of α₂δ-1 knockout on other dorsal horn pre- and postsynaptic markers, indicating the primary afferent pathways are not otherwise affected by α₂δ-1 ablation.

An overview of interventional strategies for the management of oncologic pain

Pain is a ubiquitous part of the cancer experience. Often the presenting symptom of malignancy, pain becomes more prevalent in advanced or metastatic disease and often persists despite curative treatment. Although management of cancer pain improved following publication of the WHO's analgesic ladder, when used in isolation, conservative approaches often fail to control pain and are limited by intolerable side effects. Interventional strategies provide an option for managing cancer pain that remains refractory to pharmacologic therapy. The purpose of this review is to investigate these strategies and discuss the risks and benefits which must be weighed when considering their use. Therapies anticipated to have an increasingly important role in the future of cancer pain management are also discussed.

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.

Refill Procedures of Intrathecal Drug Delivery Systems With a Recessed Fill Port on the Pump Surface: A Prospective Comparison Study of Ultrasound-Guided vs. Blind Refill Technique

OBJECTIVES

Structural differences of implantable drug delivery systems (IDDSs) might have an impact on the efficiency of needle access to the reservoir fill port (RFP). The aim of this study was to assess the efficiency of RFP needle access with an ultrasound (US)-guided vs. a blind refill technique in IDDSs with a Recessed RFP (Recessed-RFP-IDDS).

MATERIALS AND METHODS

The primary outcome was the number of attempts needed to enter the RFP with a needle comparing the US-guided technique vs. the blind refill technique. The time to enter the RFP with the needle was a secondary outcome. We compared the amount of attempts between both techniques with the non-parametric Wilcoxon rank sum test.

RESULTS

Fourteen adult patients underwent a total of 75 refills of their Recessed-RFP-IDDS during a period of 24 months. The median number of attempts to enter the RFP did not differ significantly between the US-guided technique and the blind refill technique (2.0 (IQR: 1-5) vs. 1.5 (IQR: 1-5.0), p = 0.572). The median time to enter the RFP with the needle did not differ significantly between both techniques (35.0 sec (IQR: 26.0-58.0) vs. 41.0 sec (IQR: 25.5-46.8), p = 0.878).

CONCLUSION

The results of this study suggest that there is no difference in the RFP needle access efficiency between the US-guided and the blind refill technique in superficially located Recessed-RFP-IDDSs, if performed by experienced practitioners. However, the study did not address efficiency of the RFP needle access in IDDSs with aberrancy in pump location or refills performed by inexperienced staff.

Unique aspects of clinical trials of invasive therapies for chronic pain

Nearly all who review the literature conclude that the role of invasive procedures to treat chronic pain is poorly characterized because of the lack of “definitive” studies. The overt nature of invasive treatments, along with the risks, technical skills, and costs involved create challenges to study them. However, these challenges do not completely preclude evaluating invasive procedure effectiveness and safety using well-designed methods. This article reviews the challenges of studying outcomes of invasive therapies to treat pain and discuss possible solutions. Although the following discussion can apply to most invasive therapies to treat chronic pain, it is beyond the scope of the article to individually cover every invasive therapy used. Therefore, most of the examples focus on injection therapies to treat spine pain, spinal cord stimulation, and intrathecal drug therapies.

Novel analgesic ω-conotoxins from the vermivorous cone snail Conus moncuri provide new insights into the evolution of conopeptides

Cone snails are a diverse group of predatory marine invertebrates that deploy remarkably complex venoms to rapidly paralyse worm, mollusc or fish prey. ω-Conotoxins are neurotoxic peptides from cone snail venoms that inhibit Ca_v2.2 voltage-gated calcium channel, demonstrating potential for pain management via intrathecal (IT) administration. Here, we isolated and characterized two novel ω-conotoxins, MoVIA and MoVIB from Conus moncuri, the first to be identified in vermivorous (worm-hunting) cone snails. MoVIA and MoVIB potently inhibited human Ca_v2.2 in fluorimetric assays and rat Ca_v2.2 in patch clamp studies, and both potently displaced radiolabeled ω-conotoxin GVIA (¹²⁵I-GVIA) from human SH-SY5Y cells and fish brain membranes (IC₅₀ 2–9 pM). Intriguingly, an arginine at position 13 in MoVIA and MoVIB replaced the functionally critical tyrosine found in piscivorous ω-conotoxins. To investigate its role, we synthesized MoVIB-[R13Y] and MVIIA-[Y13R]. Interestingly, MVIIA-[Y13R] completely lost Ca_v2.2 activity and MoVIB-[R13Y] had reduced activity, indicating that Arg at position 13 was preferred in these vermivorous ω-conotoxins whereas tyrosine 13 is preferred in piscivorous ω-conotoxins. MoVIB reversed pain behavior in a rat neuropathic pain model, confirming that vermivorous cone snails are a new source of analgesic ω-conotoxins. Given vermivorous cone snails are ancestral to piscivorous species, our findings support the repurposing of defensive venom peptides in the evolution of piscivorous Conidae.

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.

Synergistic antinociception between ZC88, an N-type voltage-dependent calcium channel blocker, and ibuprofen in mouse models of visceral and somatic inflammatory pain

BACKGROUND

A combination of analgesic agents with different mechanisms can induce additive or synergistic analgesia. The N-type voltage-dependent calcium channel (N-VDCC) is a novel therapeutic target for pain control. In addition to providing effective pain relief when used alone, N-VDCC blockers produce synergistic analgesia when used in combination with opiates. However, the interaction between N-VDCC blockers and nonsteroidal anti-inflammatory drugs (NSAIDs) remains unclear.

METHODS

Using isobolographic analysis and composite additive curve analysis, the antinociceptive interaction between ZC88, a selective N-VDCC blocker and ibuprofen, a classical NSAID, was investigated in two mouse models of visceral and somatic inflammatory pain.

RESULTS

In the acetic acid writhing test, both ZC88 (10.5-42 mg/kg, intraperitoneally) and ibuprofen (50-200 mg/kg, orally) produced dose-dependent antinociception, with ED₅₀ values of 27.2 and 100.5 mg/kg, respectively. ZC88 in combination with ibuprofen (ZC88 + ibuprofen) also induced significant antinociception, and isobolographic analysis revealed a synergistic interaction at 50% effect level. The experimental ED₅₀ (ED_{50 mix} ) of this combination (34.5 mg/kg) was significantly lower than the theoretical ED₅₀ (ED_{50 add} ; 63.8 mg/kg). Additionally, composite additive curve analysis displayed synergistic interaction at other effect levels. In the formalin test, ZC88 or ibuprofen alone significantly reduced late-phase rather than early-phase pain, with ED₅₀ values of 31.3 and 123.9 mg/kg, respectively. Similarly, both isobolographic analysis and composite additive curve analysis revealed synergistic antinociception of ZC88 + ibuprofen (40.6 mg/kg of ED_{50 mix} vs. 77.6 mg/kg of ED_{50 add} ).

CONCLUSION

ZC88 in combination with ibuprofen produces synergistic antinociception in mouse models of somatic and visceral inflammatory pain.

SIGNIFICANCE

Because ZC88 + ibuprofen achieves the same antinociceptive effect at lower doses, the use of this combination could result in fewer dose-related untoward effects. The potentiation of ZC88 on ibuprofen-induced antinociception indicates that N-VDCC blocker has potential benefit to treat severe inflammatory pain.

Pain therapeutics from cone snail venoms: From Ziconotide to novel non-opioid pathways

There have been numerous attempts to develop non-opioid drugs for severe pain, but the vast majority of these efforts have failed. A notable exception is Ziconotide (Prialt®), approved by the FDA in 2004. In this review, we summarize the present status of Ziconotide as a therapeutic drug and introduce a wider framework: the potential of venom peptides from cone snails as a resource providing a continuous pipeline for the discovery of non-opioid pain therapeutics. An auxiliary theme that we hope to develop is that these venoms, already a validated starting point for non-opioid drug leads, should also provide an opportunity for identifying novel molecular targets for future pain drugs. This review comprises several sections: the first focuses on Ziconotide as a therapeutic (including a historical retrospective and a clinical perspective); followed by sections on other promising Conus venom peptides that are either in clinical or pre-clinical development. We conclude with a discussion on why the outlook for discovery appears exceptionally promising. The combination of new technologies in diverse fields, including the development of novel high-content assays and revolutionary advancements in transcriptomics and proteomics, puts us at the cusp of providing a continuous pipeline of non-opioid drug innovations for pain. SIGNIFICANCE: The current opioid epidemic is the deadliest drug crisis in American history. Thus, this review on the discovery of non-opioid pain therapeutics and pathways from cone snail venoms is significant and timely.

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.

Beach to Bench to Bedside: Marine Invertebrate Biochemical Adaptations and Their Applications in Biotechnology and Biomedicine

The ocean covers more than 70% of the surface of the planet and harbors very diverse ecosystems ranging from tropical coral reefs to the deepest ocean trenches, with some of the most extreme conditions of pressure, temperature, and light. Organisms living in these environments have been subjected to strong selective pressures through millions of years of evolution, resulting in a plethora of remarkable adaptations that serve a variety of vital functions. Some of these adaptations, including venomous secretions and light-emitting compounds or ink, represent biochemical innovations in which marine invertebrates have developed novel and unique bioactive compounds with enormous potential for basic and applied research. Marine biotechnology, defined as the application of science and technology to marine organisms for the production of knowledge, goods, and services, can harness the enormous possibilities of these unique bioactive compounds acting as a bridge between biological knowledge and applications. This chapter highlights some of the most exceptional biochemical adaptions found specifically in marine invertebrates and describes the biotechnological and biomedical applications derived from them to improve the quality of human life.

G-Protein Coupled Receptors Targeted by Analgesic Venom Peptides

Chronic pain is a complex and debilitating condition associated with a large personal and socioeconomic burden. Current pharmacological approaches to treating chronic pain such as opioids, antidepressants and anticonvulsants exhibit limited efficacy in many patients and are associated with dose-limiting side effects that hinder their clinical use. Therefore, improved strategies for the pharmacological treatment of pathological pain are urgently needed. G-protein coupled receptors (GPCRs) are ubiquitously expressed on the surface of cells and act to transduce extracellular signals and regulate physiological processes. In the context of pain, numerous and diverse families of GPCRs expressed in pain pathways regulate most aspects of physiological and pathological pain and are thus implicated as potential targets for therapy of chronic pain. In the search for novel compounds that produce analgesia via GPCR modulation, animal venoms offer an enormous and virtually untapped source of potent and selective peptide molecules. While many venom peptides target voltage-gated and ligand-gated ion channels to inhibit neuronal excitability and blunt synaptic transmission of pain signals, only a small proportion are known to interact with GPCRs. Of these, only a few have shown analgesic potential in vivo. Here we review the current state of knowledge regarding venom peptides that target GPCRs to produce analgesia, and their development as therapeutic compounds.

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.