Intrathecal Analgesia for Chronic Refractory Pain: Current and Future Prospects

A novel microglia-targeting strategy based on nanoparticle-mediated delivery of miR-26a-5p for long-lasting analgesia in chronic pain

Accumulating evidence supports the notion that microglia play versatile roles in different chronic pain conditions. However, therapeutic strategies of chronic pain by targeting microglia remain largely overlooked. This study seeks to develop a miRNA-loaded nano-delivery system by targeting microglia, which could provide a decent and long-lasting analgesia for chronic pain. Surface aminated mesoporous silica nanoparticles were adopted to load miR-26a-5p, a potent analgesic miRNA, by electrostatic adsorption, which can avoid miR-26a-5p is rapidly released and degraded. Then, targeting peptide MG1 was modified on the surface of aminated mesoporous silica particles for microglia targeting. In peripheral nerve injury induced neuropathic pain model, a satisfactory anti-allodynia effect with about 6 weeks pain-relief duration were achieved through targeting microglia strategy, which decreased microglia activation and inflammation by Wnt5a, a non-canonical Wnt pathway. In inflammatory pain and chemotherapy induced peripheral neuropathic pain, microglia targeting strategy also exhibited more efficient analgesia and longer pain-relief duration than others. Overall, we developed a microglia-targeting nano-delivery system, which facilitates precisely miR-26a-5p delivery to enhance analgesic effect and duration for several chronic pain conditions.

A new approach for leptomeningeal metastases: chemotherapy administered through lumbar intrathecal port

BACKGROUND

Intrathecal chemotherapy is a local therapeutic modality used for treatment of leptomeningeal metastases. However, the techniques currently used, i.e. repeated lumbar puncture and Ommaya reservoir, have certain disadvantages. Lumbar intrathecal port (LIP) placement is a relatively novel technique, which has been used for pain management in cancer patients.

OBJECTIVE

To investigate the use of LIP for intrathecal administration of chemotherapeutic agents in patients with leptomeningeal metastases.

METHODS

Retrospective study of 13 patients treated with intrathecal chemotherapy for secondary leptomeningeal involvement of a primary solid tumor were included in this retrospective study. The patients received intrathecal chemotherapy through a LIP.

RESULTS

The patients received a total of 123 intrathecal chemotherapy doses. No grade 3-4 toxicity, technical problem or severe complication developed. During a median of 136 days of follow-up (range, 67-376 days), 12 patients died (92.3%). The treatment resulted in symptom improvement in all patients and self-rated overall health and quality of life improved, compared with baseline.

CONCLUSIONS

The LIP system, which has been used for intrathecal pain management for decades, appears to offer a safe alternative for intrathecal chemotherapy in patients with leptomeningeal metastases. Further studies are warranted to clarify its potential use in this setting.

Intrathecal drug delivery for pain management: recent advances and future developments

Introduction: Chronic pain conditions of malignant and non-malignant etiology afflict a large group of the population and pose a vast economic burden on society. Intrathecal drug therapy is a viable treatment option in such patients who have failed conservative medical measures and less invasive pain management procedures. However, the clinical growth of intrathecal therapy in managing intractable chronic pain conditions continues to face many challenges and is likely underutilized secondary to its high-complexity and lack of understanding. Areas covered: This review will briefly discuss the history of intrathecal drug delivery systems (IDDS), cerebrospinal fluid (CSF) flow dynamics, types of IDDS, indications and patient profile suitable for this therapy, and risks and complications related to IDDS. We will also discuss challenges faced by physicians utilizing this therapy and the future changes that are needed for making this treatment modality more efficacious. Expert opinion: IDDS offer an effective therapy for pain control in patients suffering from chronic intractable pain conditions. These devices provide a safer alternative to oral opioid medications with reduced systemic side effects. Adherence to best practices and continued clinical and basic science research is important to ensure continuing success of this therapy.

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.

Effects of NOP-Related Ligands in Nonhuman Primates

The nociceptin/orphanin FQ peptide (NOP) receptor-related ligands have been demonstrated in preclinical studies for several therapeutic applications. This article highlights (1) how nonhuman primates (NHP) were used to facilitate the development and application of positron emission tomography tracers in humans; (2) effects of an endogenous NOP ligand, nociceptin/orphanin FQ, and its interaction with mu opioid peptide (MOP) receptor agonists; and (3) promising functional profiles of NOP-related agonists in NHP as analgesics and treatment for substance use disorders. NHP models offer the most phylogenetically appropriate evaluation of opioid and non-opioid receptor functions and drug effects. Based on preclinical and clinical data of ligands with mixed NOP/MOP receptor agonist activity, several factors including their intrinsic efficacies for activating NOP versus MOP receptors and different study endpoints in NHP could contribute to different pharmacological profiles. Ample evidence from NHP studies indicates that bifunctional NOP/MOP receptor agonists have opened an exciting avenue for developing safe, effective medications with fewer side effects for treating pain and drug addiction. In particular, bifunctional NOP/MOP partial agonists hold a great potential as (1) effective spinal analgesics without itch side effects; (2) safe, nonaddictive analgesics without opioid side effects such as respiratory depression; and (3) effective medications for substance use disorders.

Evaluation of intrathecal drug delivery system for intractable pain in advanced malignancies: A prospective cohort study

Pain is prevalent in advanced malignancies; however, some patients cannot get adequate pain relief by conservative routes of analgesic administration or experience serious side effects related to high dose of opioids. For those who have exhausted multimodal conservative analgesic, intrathecal drug delivery is an alternative intervention for truly effective pain management. The objective of this study was to evaluate the clinical efficacy and safety of intrathecal drug delivery system (IDDS) for the treatment of intractable pain in advanced cancer patients.A prospective cohort study was performed between July 2015 and October 2016. Fifty-three patients undergoing intractable cancer-related pain or intolerable drug-related adverse effects were recruited and received IDDS therapy with a patient-controlled intrathecal analgesia pump. The assessment was conducted during admission, in titration period, and followed up monthly to death by scheduled refill visits. Pain numeric rating scale scores, comprehensive toxicity scores, quality of life scores, systemic opioid use (basal and breakthrough dose), intrathecal morphine use (basal and patient-controlled intrathecal analgesia dose), and complications were recorded to evaluate the curative effect and safety.Between baseline and all subsequent follow-ups, statistically significant decreases in pain numeric rating scale scores and comprehensive toxicity scores were verified. A statistical improvement in quality of life scores was found after starting IDDS therapy. Both basal and breakthrough doses of systemic opioid showed a significant decrease during the follow-up period. And there was a modest escalation in the intrathecal morphine dose throughout the duration of study. No infective, device-related, and catheter-related complications were observed.The findings showed that IDDS therapy allowed for rapid and highly effective pain relief with less toxicity in comparison to conservative medications. Patients with advanced malignancies would also benefit from an improvement in the life quality after the procedure. IDDS therapy represented a valuable option for intractable cancer-related pain management.

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.