Chronic phantom limb pain: the effects of calcitonin, ketamine, and their combination on pain and sensory thresholds

Approaches to neuropathic amputation-related pain: narrative review of surgical, interventional, and medical treatments

BACKGROUND/IMPORTANCE

Neuropathic amputation-related pain can consist of phantom limb pain (PLP), residual limb pain (RLP), or a combination of both pathologies. Estimated of lifetime prevalence of pain and after amputation ranges between 8% and 72%.

OBJECTIVE

This narrative review aims to summarize the surgical and non-surgical treatment options for amputation-related neuropathic pain to aid in developing optimized multidisciplinary and multimodal treatment plans that leverage multidisciplinary care.

EVIDENCE REVIEW

A search of the English literature using the following keywords was performed: PLP, amputation pain, RLP. Abstract and full-text articles were evaluated for surgical treatments, medical management, regional anesthesia, peripheral block, neuromodulation, spinal cord stimulation, dorsal root ganglia, and peripheral nerve stimulation.

FINDINGS

The evidence supporting most if not all interventions for PLP are inconclusive and lack high certainty. Targeted muscle reinnervation and regional peripheral nerve interface are the leading surgical treatment options for reducing neuroma formation and reducing PLP. Non-surgical options include pharmaceutical therapy, regional interventional techniques and behavioral therapies that can benefit certain patients. There is a growing evidence that neuromodulation at the spinal cord or the dorsal root ganglia and/or peripheral nerves can be an adjuvant therapy for PLP.

CONCLUSIONS

Multimodal approaches combining pharmacotherapy, surgery and invasive neuromodulation procedures would appear to be the most promising strategy for preventive and treating PLP and RLP. Future efforts should focus on cross-disciplinary education to increase awareness of treatment options exploring best practices for preventing pain at the time of amputation and enhancing treatment of chronic postamputation pain.

Phantom limb syndrome: from pathogenesis to treatment. A narrative review

Phantom Limb Syndrome (PLS) can be defined as the disabling or painful sensation of the presence of a body part that is no longer present after its amputation. Anatomical changes involved in Phantom Limb Syndrome, occurring at peripheral, spinal and brain levels and include the formation of neuromas and scars, dorsal horn sensitization and plasticity, short-term and long-term modifications at molecular and topographical levels. The molecular reorganization processes of Phantom Limb Syndrome include NMDA receptors hyperactivation in the dorsal horn of the spinal column leading to inflammatory mechanisms both at a peripheral and central level. At the brain level, a central role has been recognized for sodium channels, BDNF and adenosine triphosphate receptors. In the paper we discuss current available pharmacological options with a final overview on non-pharmacological options in the pipeline.

Assessing suicide risk in chronic pain management: a narrative review across drug classes

INTRODUCTION

Chronic pain presents a multifaceted challenge in clinical practice, necessitating a nuanced understanding of pharmacological interventions to optimize treatment outcomes. This review provides an outline of various pharmacological agents commonly used in chronic pain management and highlights their safety considerations, particularly regarding suicide risk.

AREAS COVERED

This review discusses the role of antidepressants, anticonvulsants, GABA receptor agonists, NMDA receptor antagonists, corticosteroids, cannabis and cannabinoids, bisphosphonates, calcitonin, and alpha-2 adrenergic receptor agonists in chronic pain management. It assesses their therapeutic benefits, potential for misuse, and psychiatric adverse effects, including the risk of suicide. Each pharmacological class is evaluated in terms of its efficacy, safety profile, and considerations for clinical practice. We searched peer-reviewed English literature on the topic using the MEDLINE database without time restrictions.

EXPERT OPINION

While pharmacological interventions offer promise in alleviating chronic pain, healthcare providers must carefully weigh their benefits against potential risks, including the risk of exacerbating psychiatric symptoms and increasing suicide risk. Individualized treatment approaches, close monitoring, and multidisciplinary collaboration are essential for optimizing pain management strategies while mitigating adverse effects. Ongoing research efforts are crucial for advancing our understanding of these pharmacological interventions and refining pain management practices.

Pretreatment Brain White Matter Integrity Associated With Neuropathic Pain Relief and Changes in Temporal Summation of Pain Following Ketamine

Neuropathic pain (NP) is a prevalent condition often associated with heightened pain responsiveness suggestive of central sensitization. Neuroimaging biomarkers of treatment outcomes may help develop personalized treatment strategies, but white matter (WM) properties have been underexplored for this purpose. Here we assessed whether WM pathways of the default mode network (DMN: medial prefrontal cortex [mPFC], posterior cingulate cortex, and precuneus) and descending pain modulation system (periaqueductal gray [PAG]) are associated with ketamine analgesia and attenuated temporal summation of pain (TSP, reflecting central sensitization) in NP. We used a fixel-based analysis of diffusion-weighted imaging data to evaluate WM microstructure (fiber density [FD]) and macrostructure (fiber bundle cross-section) within the DMN and mPFC-PAG pathways in 70 individuals who underwent magnetic resonance imaging and TSP testing; 35 with NP who underwent ketamine treatment and 35 age- and sex-matched pain-free individuals. Individuals with NP were assessed before and 1 month after treatment; those with ≥30% pain relief were considered responders (n = 18), or otherwise as nonresponders (n = 17). We found that WM structure within the DMN and mPFC-PAG pathways did not differentiate responders from nonresponders. However, pretreatment FD in the anterior limb of the internal capsule correlated with pain relief (r=.48). Moreover, pretreatment FD in the DMN (left mPFC-precuneus/posterior cingulate cortex; r=.52) and mPFC-PAG (r=.42) negatively correlated with changes in TSP. This suggests that WM microstructure in the DMN and mPFC-PAG pathway is associated with the degree to which ketamine reduces central sensitization. Thus, fixel metrics of WM structure may hold promise to predict ketamine NP treatment outcomes. PERSPECTIVE: We used advanced fixel-based analyses of MRI diffusion-weighted imaging data to identify pretreatment WM microstructure associated with ketamine outcomes, including analgesia and markers of attenuated central sensitization. Exploring associations between brain structure and treatment outcomes could contribute to a personalized approach to treatment for individuals with NP.

Integrating mechanistic-based and classification-based concepts into perioperative pain management: an educational guide for acute pain physicians

Chronic pain begins with acute pain. Physicians tend to classify pain by duration (acute vs chronic) and mechanism (nociceptive, neuropathic and nociplastic). Although this taxonomy may facilitate diagnosis and documentation, such categories are to some degree arbitrary constructs, with significant overlap in terms of mechanisms and treatments. In clinical practice, there are myriad different definitions for chronic pain and a substantial portion of chronic pain involves mixed phenotypes. Classification of pain based on acuity and mechanisms informs management at all levels and constitutes a critical part of guidelines and treatment for chronic pain care. Yet specialty care is often siloed, with advances in understanding lagging years behind in some areas in which these developments should be at the forefront of clinical practice. For example, in perioperative pain management, enhanced recovery protocols are not standardized and tend to drive treatment without consideration of mechanisms, which in many cases may be incongruent with personalized medicine and mechanism-based treatment. In this educational document, we discuss mechanisms and classification of pain as it pertains to commonly performed surgical procedures. Our goal is to provide a clinical reference for the acute pain physician to facilitate pain management decision-making (both diagnosis and therapy) in the perioperative period.

Efficacy and Safety of Ketamine to Treat Cancer Pain in Adult Patients: A Systematic Review

CONTEXT

Ketamine is a well-characterized anesthetic agent, and subanesthetic ketamine possesses analgesic effects in both acute and chronic pain.

OBJECTIVES

A systematic review was performed to ascertain the efficacy and safety of ketamine in treating pain for cancer patients.

METHODS

Eight databases were searched from the inception to March 20th, 2023 to obtain randomized controlled trials (RCTs) on ketamine for treating pain in cancer patients. Two reviewers independently screened studies, extracted the data and assessed the risk of bias of included studies; then, meta-analysis was performed by using Revman 5.3 software and Stata 14.0 software.

RESULTS

Thirty-five studies were included, involving 2279 patients with cancer pain. The results of meta-analysis showed that ketamine could significantly reduce pain intensity. Subgroup analysis revealed that, when compared with control group, ketamine decreased markedly visual analogue scale (VAS) scores in two days after the end of treatment with ketamine, and ketamine administrated by patient controlled epidural analgesia (PCEA) was effective. Meanwhile, ketamine could significantly reduce the number of patient-controlled analgesia (PCA) compressions within 24 hours and morphine dosage. Ketamine could not decrease Ramsay sedation score. Additionally, the adverse events significantly decreased in the ketamine group, including nausea and vomiting, constipation, pruritus, lethargy, uroschesis, hallucination, and respiratory depression. In addition, compared with the control group, ketamine could reduce Hamilton depression scale (HAMD) score and relieve depressive symptoms.

CONCLUSION

Ketamine may be used as an effective therapy to relieve cancer pain. However, more rigorously designed RCTs with larger sample sizes are required to verify the above conclusions.

Maintenance IV Ketamine Therapy in the Fibromyalgia Patient: A Case Report

Introduction

Fibromyalgia is a complex disorder characterized by distributed and persistent pain often associated with fatigue and depression. The underlying causal agents of this dysfunction are not clear. Ketamine has been used to treat chronic pain in a variety of pain syndromes, including fibromyalgia, but the dosing protocols used are neither standardized nor consistent across cases. The current case presents an opportunity to contribute to a progression towards a consensus on ketamine dosing for fibromyalgia.

Case Presentation

A 60-year-old female presented with indications of fibromyalgia and was administered a 9-session IV ketamine treatment for pain. The initial dosing was 50 mg, with a concentration of 1.0 mg/ml at an infusion rate of 0.8 mg/kg/hr. This was increased to 200 mg and eventually to 240 mg, maintaining a ketamine concentration 4.0-4.8 mg/ml at an infusion rate of 1.5 mg/kg/hr.

Management and Outcomes

Following the first 9-session therapy, the patient reported >50% pain relief from pre-infusion levels and was placed on a maintenance regimen in perpetuity. This regimen involves two monthly IV ketamine infusions, one day apart for two hours at a maintenance rate of 4.8 mg/kg/hr.

Conclusion

Ketamine by IV is an effective option for pain management in patients with fibromyalgia. Compared to previous case studies, it is recommended that increased total dose, frequent administration, and longer duration of infusions all may be necessary for ketamine to maximize its beneficial effects.

Simultaneous application of lidocaine and ketamine during ambulatory infusion therapy: a retrospective analysis

Background: Infusions with lidocaine or ketamine have been separately established in the treatment of chronic pain. This study aims to retrospectively evaluate the effect of combined infusions of lidocaine and ketamine. Materials & methods: Patient records were screened for receipt of combined ambulatory infusions of lidocaine and ketamine from 2012 through 2021. A scoring system was designed to assess pain response retrospectively. Results: A total of 319 patients were included. Median pain reduction in days was 10.00 (interquartile range: 13.25). Side effects were limited to the acute phase of infusions. A total of 41.4% of patients who received concomitant pain medication reported a dose reduction. Conclusion: Our data support combined infusions as a safe therapy option, with good short-, medium- and long-term reductions in pain and great heterogeneity in treatment response. Clinical trial registration: ClinicalTrials.gov (NCT05103319).

Predictive factors of success and failure for intravenous ketamine therapy in patients suffering from chronic neuropathic pain

Background

Intravenous (IV) ketamine is used for chronic neuropathic pain refractory to other treatments. Administration of such a medication requires high-cost services while the result is not always satisfactory with a significant percentage of failure. Success and failure are related to some factors.

Method

In this study, we aim to point the most responsive disease category to IV ketamine and the predictive factors for successful and failed treatment. Two hundred and sixty-nine patients out of 371 were included. Demographic, clinical, and therapy-related variables were retrospectively collected and then statistically analyzed using various descriptive and inferential methods. A few descriptive statistics are obtained for the variables depending on their nature (e.g., percentages for qualitative variables and means for quantitative variables). Furthermore, several inferential methods are considered to address some statistical points of interest, including, but not limited to, odds ratio interpretations via logistic regression as well as association and correlation analyses.

Results

A significant association was found between the presence of intermittent pain pattern as well as the pain of chronic primary category and favorable response to IV ketamine while the history of previous analgesic interventions was significantly associated with a negative response.

Conclusion

The identified factors can be used to prospectively study the efficacy of ketamine using selection criteria based on the observed results in our study to re-evaluate the percentage of responsiveness according to these new parameters.

Calcitonin in the Treatment of Phantom Limb Pain: A Systematic Review

INTRODUCTION

Phantom limb pain (PLP) refers to pain perceived in a part of the body removed by amputation or trauma. Despite the high prevalence of PLP following amputation and the significant morbidity associated with it, robust therapeutic approaches are currently lacking. Calcitonin, a polypeptide hormone, has recently emerged as a novel analgesic with documented benefits in the treatment of several pain-related conditions.

METHODS

We present a systematic review that comprehensively evaluates the analgesic effects of calcitonin for patients with PLP. We searched MEDLINE, OLDMEDLINE, and PubMed Central databases with the key words "calcitonin" "phantom limb pain" and "phantom pain" to identify clinical studies evaluating the efficacy or effectiveness of calcitonin administration, in any form and dose, for the treatment of PLP. Additionally, Google Scholar was searched manually with the search term "calcitonin phantom limb pain". All four databases were searched from inception until 1 December 2022. The methodological quality of each included study was assessed using the Downs and Black checklist and the GRADE criteria were used to assess effect certainty and risk of bias.

RESULTS

Our search identified 4108 citations, of which six ultimately met the criteria for inclusion in the synthesis. The included articles described a mix of open-label (n = 2), prospective observational cohort (n = 1), and randomized clinical trials (n = 3). The most common treatment regimen in the current literature is a single intravenous infusion of 200 IU salmon-derived calcitonin.

CONCLUSION

The available evidence supported the use of calcitonin as either monotherapy or adjuvant therapy in the treatment of PLP during the acute phase, while the evidence surrounding calcitonin treatment in chronic PLP is heterogeneous. Given the limited treatment options for the management of PLP and calcitonin's relatively wide therapeutic index, further research is warranted to determine the role that calcitonin may play in the treatment of PLP and other pain disorders.

Perioperative Management of Painful Phantom Limb Syndrome: A Narrative Review and Clinical Management Proposal

Objective: Painful Phantom Limb Syndrome (PPLS) occurs in 50 to 80% of patients undergoing amputation, having a great impact on quality of life, productivity and psychosocial sphere. The objective of this review is to summarize the pharmacological and non-pharmacological strategies, surgical optimization, and provide a multidisciplinary approach aimed at reducing the incidence of chronic pain associated with PPLS in patients undergoing limb amputation.Methods: A narrative review was carried out using Medline, Pubmed, Proquest, LILACS and Cochrane, searching for articles between 2000 and 2021. Articles describing the epidemiology, pathophysiological considerations, and current treatments were selected after a screening process.Results: A multidisciplinary and multimodal approach is required in PPLS, and should include the use of regional techniques, and adjuvants such as NSAIDs, ketamine, lidocaine and gabapentinoids. In addition, an evaluation and continuous management of risk factors for chronic pain in conjunction with the surgical team is necessary.Conclusion: The current literature does not support that a single technique is effective in the prevention of PPLS. However, adequate acute pain control, rehabilitation and early restoration of the body scheme under a multidisciplinary and multimodal approach have shown benefit in the acute setting.

Combination pharmacotherapy for the treatment of neuropathic pain in adults: systematic review and meta-analysis

ABSTRACT

Neuropathic pain causes substantial morbidity and healthcare utilization. Monotherapy with antidepressants or anticonvulsants often fails to provide relief. Combining different drugs sometimes provides improved analgesia and/or tolerability. More than half of patients receive 2 or more analgesics, and combination trials continue to emerge. This review comprehensively searched CENTRAL, MEDLINE, and EMBASE for relevant trials. Included studies are double-blind randomized controlled trials evaluating combinations of 2 or more drugs vs placebo or at least one monotherapy in adults with neuropathic pain. Outcomes included measures of efficacy and adverse effects. Risk of bias was assessed. Meta-analyses compared combination to monotherapy wherever 2 or more similar studies were available. Forty studies (4741 participants) were included. Studies were heterogenous with respect to various characteristics, including dose titration methods and administration (ie, simultaneous vs sequential) of the combination. Few combinations involved a nonsedating drug, and several methodological problems were identified. For opioid-antidepressant, opioid-gabapentinoid, and gabapentinoid-antidepressant combinations, meta-analyses failed to demonstrate superiority over both monotherapies. In general, adverse event profiles were not substantially different for combination therapy compared with monotherapy. Despite widespread use and a growing number of trials, convincing evidence has not yet emerged to suggest superiority of any combination over its respective monotherapies. Therefore, implementing combination therapy-as second- or third-line treatment-in situations where monotherapy is insufficient, should involve closely monitored individual dosing trials to confirm safety and overall added benefit. Further research is needed, including trials of combinations involving nonsedating agents, and to identify clinical settings and specific combinations that safely provide added benefit.

An Algorithm Approach to Phantom Limb Pain

Phantom limb pain (PLP) is a common condition that occurs following both upper and lower limb amputation. First recognized and described in 1551 by Ambroise Pare, research into its underlying pathology and effective treatments remains a very active and growing field. To date, however, there is little consensus regarding the optimal management of phantom limb pain. With few large well-designed clinical trials of which to make treatment recommendations, as well as significant heterogeneity in clinical response to available treatments, the management of PLP remains challenging. Below we summarize the current state of knowledge in the field, as well as propose an algorithm for the approach to the treatment of PLP.

Targeting Affective Mood Disorders With Ketamine to Prevent Chronic Postsurgical Pain

The phencyclidine-derivative ketamine [2-(2-chlorophenyl)-2-(methylamino)cyclohexan-1-one] was added to the World Health Organization's Model List of Essential Medicines in 1985 and is also on the Model List of Essential Medicines for Children due to its efficacy and safety as an intravenous anesthetic. In sub-anesthetic doses, ketamine is an effective analgesic for the treatment of acute pain (such as may occur in the perioperative setting). Additionally, ketamine may have efficacy in relieving some forms of chronic pain. In 2019, Janssen Pharmaceuticals received regulatory-approval in both the United States and Europe for use of the S-enantiomer of ketamine in adults living with treatment-resistant major depressive disorder. Pre-existing anxiety/depression and the severity of postoperative pain are risk factors for development of chronic postsurgical pain. An important question is whether short-term administration of ketamine can prevent the conversion of acute postsurgical pain to chronic postsurgical pain. Here, we have reviewed ketamine's effects on the biopsychological processes underlying pain perception and affective mood disorders, focusing on non-NMDA receptor-mediated effects, with an emphasis on results from human trials where available.

Ketamine for the Treatment of Chronic Pain: A Comprehensive Review

Background

Chronic pain significantly worsens the quality of life. Unlike neuropathic, musculoskeletal, postoperative pain, and cancer pain, chronic primary pain cannot be explained by an underlying disease or condition, making its treatment arduous.

Objectives

This manuscript intends to provide a comprehensive review of the use of ketamine as a treatment option for specific chronic pain conditions.

Study Design

A review article.

Setting

A review of the literature.

Methods

A search was done on PubMed for relevant articles.

Results

A comprehensive review of the current understanding of chronic pain and the treatment of specific chronic pain conditions with ketamine.

Limitations

Literature is scarce regarding the use of ketamine for the treatment of chronic pain.

Conclusion

First-line treatment for many chronic pain conditions includes NSAIDs, antidepressants, anticonvulsants, and opioids. However, these treatment methods are unsuccessful in a subset of patients. Ketamine has been explored in randomized controlled trials (RCTs) as an alternative treatment option, and it has been demonstrated to improve pain symptoms, patient satisfaction, and quality of life. Conditions highlighted in this review include neuropathic pain, fibromyalgia, complex regional pain syndrome (CRPS), phantom limb pain (PLP), cancer pain, and post-thoracotomy pain syndrome. This review will discuss conditions, such as neuropathic pain, fibromyalgia, complex regional pain syndrome, and more and ketamine's efficacy and its supplementary benefits in the chronic pain patient population. As the opioid crisis in the United States continues to persist, this review aims to understand better multimodal analgesia, which can improve how chronic pain is managed.

Auricular Therapy for Treating Phantom Limb Pain Accompanied by Jumping Residual Limb: A Short Review and Case Study

Phantom limb pain (PLP) is a common complaint among patients after amputation, while jumping residual limb is a rare post-amputation complication, they rarely happen at the same time and both remain difficult to manage. At present, there is a paucity of literature on this topic, and no treatment has been proven effective for treating both of them. In the present brief report, we described a patient who developed severe PLP accompanied by jumping residual limb after below-the-knee amputation and she was treated by auricular therapy (AT) with satisfactory effect.

Ketamine-50 years in use: from anesthesia to rapid antidepressant effects and neurobiological mechanisms

Over the past 50 years, ketamine has solidified its position in both human and veterinary medicine as an important anesthetic with many uses. More recently, ketamine has been studied and used for several new indications, ranging from chronic pain to drug addiction and post-traumatic stress disorder. The discovery of the rapid-acting antidepressant effects of ketamine has resulted in a surge of interest towards understanding the precise mechanisms driving its effects. Indeed, ketamine may have had the largest impact for advancements in the research and treatment of psychiatric disorders in the past few decades. While intense research efforts have been aimed towards uncovering the molecular targets underlying ketamine's effects in treating depression, the underlying neurobiological mechanisms remain elusive. These efforts are made more difficult by ketamine's complex dose-dependent effects on molecular mechanisms, multiple pharmacologically active metabolites, and a mechanism of action associated with the facilitation of synaptic plasticity. This review aims to provide a brief overview of the different uses of ketamine, with an emphasis on examining ketamine's rapid antidepressant effects spanning molecular, cellular, and network levels. Another focus of the review is to offer a perspective on studies related to the different doses of ketamine used in antidepressant research. Finally, the review discusses some of the latest hypotheses concerning ketamine's action.

Clinical updates on phantom limb pain

Phantom limb pain is highly prevalent after amputation. Treatment results will probably benefit from an interdisciplinary team and individually adapted surgical, prosthetic and pain medicine approaches.

Introduction:

Most patients with amputation (up to 80%) suffer from phantom limb pain postsurgery. These are often multimorbid patients who also have multiple risk factors for the development of chronic pain from a pain medicine perspective. Surgical removal of the body part and sectioning of peripheral nerves result in a lack of afferent feedback, followed by neuroplastic changes in the sensorimotor cortex. The experience of severe pain, peripheral, spinal, and cortical sensitization mechanisms, and changes in the body scheme contribute to chronic phantom limb pain. Psychosocial factors may also affect the course and the severity of the pain. Modern amputation medicine is an interdisciplinary responsibility.

Methods:

This review aims to provide an interdisciplinary overview of recent evidence-based and clinical knowledge.

Results:

The scientific evidence for best practice is weak and contrasted by various clinical reports describing the polypragmatic use of drugs and interventional techniques. Approaches to restore the body scheme and integration of sensorimotor input are of importance. Modern techniques, including apps and virtual reality, offer an exciting supplement to already established approaches based on mirror therapy. Targeted prosthesis care helps to obtain or restore limb function and at the same time plays an important role reshaping the body scheme.

Discussion:

Consequent prevention and treatment of severe postoperative pain and early integration of pharmacological and nonpharmacological interventions are required to reduce severe phantom limb pain. To obtain or restore body function, foresighted surgical planning and technique as well as an appropriate interdisciplinary management is needed.

[Perioperative measures for prevention of phantom pain: an evidence-based approach to risk reduction]

Prevention of phantom limb pain is one of the biggest and still largely unsolved challenges in perioperative medicine. Despite many study efforts and optimization of postoperative pain treatment over the last 30 years, a significant reduction in the incidence of phantom limb pain has not been achieved. Current studies have also shown that at least 50% of patients develop phantom pain after 6 months. A possible approach could be to combine multiple synergistic interventions and implement them as a perioperative phantom pain management strategy bundle. In addition to regional anesthesia, NMDA antagonists, gabapentinoids, antidepressants and systemic lidocaine could play a relevant role. The aim of this pharmacological intervention was the modification of the pathophysiological changes in peripheral nerves and in the central nervous system after amputation.

[Calcitonin as an analgesic agent: review of mechanisms of action and clinical applications]

BACKGROUND AND OBJECTIVES

Calcitonin is a polypeptide hormone regulating the metabolism calcium in the body. For many years calcitonin has been used to maintain and improve bone mineral density and to reduce the fracture rate. Many studies showed that calcitonin had analgesic role in several painful circumstances. This pain-ameliorating effect is irrelevant to its osteoclastic inhibitory effect and mechanisms like altering Na+ channel and serotonin receptor expression or hypothesis including the endorphin-mediated mechanism were used to explain this effect. In this study we performed a thorough review on the role of calcitonin as an analgesic agent in different scenarios and investigated the fact that calcitonin can be a feasible medication to relieve pain.

METHOD

Many studies focused on the analgesic effect of calcitonin in several painful circumstances, including acute pains related to vertebral fractures, metastasis, migraine and reflex sympathetic dystrophy as well as neuropathic pains related to spinal injuries or diabetes, and phantom pain. Also, calcitonin was showed to be a useful additive to local anesthesia in the case of controlling postoperative pain or trigeminal neuralgia more effectively. However we faced some contradictory data for conditions like lumbar canal stenosis, complex regional pain syndrome, phantom pain and malignancies.

CONCLUSION

This study showed that calcitonin could be helpful analgesic agent in different painful situations. Calcitonin can be considered an eligible treatment for acute pains related to vertebral fractures and a feasible alternative for the treatment of the acute and chronic neuropathic pains where other medications might fail.

Calcitonin as an analgesic agent: review of mechanisms of action and clinical applications

Background and objectives

Calcitonin is a polypeptide hormone regulating the metabolism of calcium in the body. For many years calcitonin has been used to maintain and improve bone mineral density and to reduce the fracture rate. Many studies showed that calcitonin had analgesic role in several painful circumstances. This pain-ameliorating effect is irrelevant to its osteoclastic inhibitory effect and mechanisms like altering Na+ channel and serotonin receptor expression or hypothesis including the endorphin-mediated mechanism were used to explain this effect. In this study we performed a thorough review on the role of calcitonin as an analgesic agent in different scenarios and investigated the fact that calcitonin can be a feasible medication to relieve pain.

Method

Many studies focused on the analgesic effect of calcitonin in several painful circumstances, including acute pains related to vertebral fractures, metastasis, migraine and reflex sympathetic dystrophy as well as neuropathic pains related to spinal injuries or diabetes, and phantom pain. Also, calcitonin was showed to be a useful additive to local anesthesia in the case of controlling postoperative pain or trigeminal neuralgia more effectively. However we faced some contradictory data for conditions like lumbar canal stenosis, complex regional pain syndrome, phantom pain and malignancies.

Conclusion

This study showed that calcitonin could be helpful analgesic agent in different painful situations. Calcitonin can be considered an eligible treatment for acute pains related to vertebral fractures and a feasible alternative for the treatment of the acute and chronic neuropathic pains where other medications might fail.

Ketamine applications beyond anesthesia - A literature review

Ketamine's clinical use began in the 1970s. Physicians benefited from its safety and ability to induce short-term anesthesia and analgesia. The psychodysleptic effects caused by the drug called its further clinical use into question. Despite these unpleasant effects, ketamine is still applied in veterinary medicine, field medicine, and specialist anesthesia. Recent intensive research brought into light new possible applications of this drug. It began to be used in acute, chronic and cancer pain management. Most interesting reports come from research on the antidepressive and antisuicidal properties of ketamine giving hope for the creation of an effective treatment for major depressive disorder. Other reports highlight the possible use of ketamine in treating addiction, asthma and preventing cancer growth. Besides clinical use, the drug is also applied to in animal model of schizophrenia. It seems that nowadays, with numerous possible applications, the use of ketamine has returned; to its former glory. Nevertheless, the drug must be used with caution because still the mechanisms by which it executes its functions and long-term effects of its use are not fully known. This review aims to discuss the well-known and new promising applications of ketamine.

A Systematic Review of NMDA Receptor Antagonists for Treatment of Neuropathic Pain in Clinical Practice

OBJECTIVE

To investigate the efficacy of N-methyl-D-aspartate receptor (NMDAR) antagonists for neuropathic pain (NeuP) and review literature to determine if specific pharmacologic agents provide adequate NeuP relief.

METHODS

Literature was reviewed on PubMed using a variety of key words for 8 NMDAR antagonists. These key words include: "Ketamine and Neuropathy," "Ketamine and Neuropathic Pain," "Methadone and Neuropathy," "Methadone and Neuropathic Pain," "Memantine and Neuropathic pain," "Memantine and Neuropathy," "Amantadine and Neuropathic Pain," "Amantadine and Neuropathy," "Dextromethorphan and Neuropathic Pain," "Dextromethorphan and Neuropathy," "Carbamazepine and Neuropathic Pain," "Carbamazepine and Neuropathy," "Valproic Acid and Neuropathy," "Valproic Acid and Neuropathic Pain," "Phenytoin and Neuropathy," and "Phenytoin and Neuropathic Pain." With the results, the papers were reviewed using the PRISMA (Preferred Reporting in Systematic and Meta-Analyses) guideline.

RESULTS

A total of 58 randomized controlled trials were reviewed among 8 pharmacologic agents, which are organized by date and alphabetical order. Of the trials for ketamine, 15 showed some benefit for analgesia. Methadone had 3 positive trials, while amantadine and memantine each only had 2 trials showing NeuP analgesic properties. Dextromethorphan and valproic acid both had 4 randomized controlled trials that showed some NeuP treatment benefit while carbamazepine had over 8 trials showing efficacy. Finally, phenytoin only had 1 trial that showed clinical response in treatment.

CONCLUSIONS

There are a variety of NMDAR antagonist agents that should be considered for treatment of NeuP. Nevertheless, continued and further investigation of the 8 pharmacologic agents is needed to continue to evaluate their efficacy for treatment of NeuP.

Coping with Phantom Limb Pain

Phantom limb pain is a chronic neuropathic pain that develops in 45-85% of patients who undergo major amputations of the upper and lower extremities and appears predominantly during two time frames following an amputation: the first month and later about 1 year. Although in most patients the frequency and intensity of pain diminish over time, severe pain persists in about 5-10%. It has been proposed that factors in both the peripheral and central nervous systems play major roles in triggering the development and maintenance of pain associated with extremity amputations. Chronic pain is physically and mentally debilitating, affecting an individual's capacity for self-care, but also diminishing an individual's daily capacity for personal and economic independence. In addition, the pain may lead to depression and feelings of hopelessness. A National Center for Biotechnology Information study found that in the USA alone, the annual cost of dealing with neuropathic pain is more than $600 billion, with an estimated 20 million people in the USA suffering from this condition. Although the pain can be reduced by antiepileptic drugs and analgesics, they are frequently ineffective or their side effects preclude their use. The optimal approach for eliminating neuropathic pain and improving individuals' quality of life is the development of novel techniques that permanently prevent the development and maintenance of neuropathic pain, or that eliminate the pain once it has developed. What is still required is understanding when and where an effective novel technique must be applied, such as onto the nerve stump of the transected peripheral axons, dorsal root ganglion neurons, spinal cord, or cortex to induce the desired influences. This review, the second of two in this journal volume, examines the techniques that may be capable of reducing or eliminating chronic neuropathic pain once it has developed. Such an understanding will improve amputees' quality of life by blocking the mechanisms that trigger and/or maintain PLP and chronic neuropathic pain.

Pain Management in Athletes With Impairment: A Narrative Review of Management Strategies

OBJECTIVE

To review the literature related to different treatment strategies for the general population of individuals with amputation, spinal cord injury, and cerebral palsy, as well as how this may impact pain management in a correlated athlete population.

DATA SOURCES

A comprehensive literature search was performed linking pain with terms related to different impairment types.

MAIN RESULTS

There is a paucity in the literature relating to treatment of pain in athletes with impairment; however, it is possible that the treatment strategies used in the general population of individuals with impairment may be translated to the athlete population. There are a wide variety of treatment options including both pharmacological and nonpharmacological treatments which may be applicable in the athlete.

CONCLUSIONS

It is the role of the physician to determine which strategy of the possible treatment options will best facilitate the management of pain in the individual athlete in a sport-specific setting.

Ketamine infusion therapy for chronic pain management in South Korea: A national survey for pain physicians with a narrative review

Although ketamine infusion therapy (KIT) has been used extensively for the treatment of chronic persistent pain, there remains high heterogeneity in the administration protocols. The aim of this study was to assess the current clinical use and the infusion protocols of KIT in South Korea and to compare the protocol details with previous relevant studies.In the first phase, an online survey about KIT, including protocol information, was distributed to pain physicians managing chronic pain patients at 47 teaching hospitals registered in the Korean Pain Society. In the second phase, a review of the KIT protocols in previous clinical studies was conducted and compared with the survey results.Among 47 institutions, 35 replied; among them, 25 institutions performed KIT on an outpatient basis. The administration protocol for KIT varied greatly among institutions: the total infusion dose of ketamine ranged from 3.5 to 140 mg/70 kg, with a mode of 70 mg [interquartile range (IQR): 62.0; 8.0-70.0 mg] administered in 1 to 3 hours. In 10 previous studies of outpatient KIT, the total dose of ketamine ranged from 12.6 to 98 mg/70 kg, with a mode of 35 mg [IQR: 40 mg; 23-63 mg] given in 1 to 4 hours, which was significantly lower than in our results (P = .01). In the survey, physicians listed hallucination as the most frequent side effect.Although KIT is used in Korean pain centers, there is wide variation regarding the specific infusion protocols. The total dose of ketamine used in South Korea is significantly higher than the general recommendations for outpatient management and may compromise patient safety. The results of this survey reinforce the need for specific guidelines for KIT in managing chronic pain that counterbalance its risks and benefits.

Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Chronic Pain From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists

BACKGROUND

Over the past 2 decades, the use of intravenous ketamine infusions as a treatment for chronic pain has increased dramatically, with wide variation in patient selection, dosing, and monitoring. This has led to a chorus of calls from various sources for the development of consensus guidelines.

METHODS

In November 2016, the charge for developing consensus guidelines was approved by the boards of directors of the American Society of Regional Anesthesia and Pain Medicine and, shortly thereafter, the American Academy of Pain Medicine. In late 2017, the completed document was sent to the American Society of Anesthesiologists' Committees on Pain Medicine and Standards and Practice Parameters, after which additional modifications were made. Panel members were selected by the committee chair and both boards of directors based on their expertise in evaluating clinical trials, past research experience, and clinical experience in developing protocols and treating patients with ketamine. Questions were developed and refined by the committee, and the groups responsible for addressing each question consisted of modules composed of 3 to 5 panel members in addition to the committee chair. Once a preliminary consensus was achieved, sections were sent to the entire panel, and further revisions were made. In addition to consensus guidelines, a comprehensive narrative review was performed, which formed part of the basis for guidelines.

RESULTS

Guidelines were prepared for the following areas: indications; contraindications; whether there was evidence for a dose-response relationship, or a minimum or therapeutic dose range; whether oral ketamine or another N-methyl-D-aspartate receptor antagonist was a reasonable treatment option as a follow-up to infusions; preinfusion testing requirements; settings and personnel necessary to administer and monitor treatment; the use of preemptive and rescue medications to address adverse effects; and what constitutes a positive treatment response. The group was able to reach consensus on all questions.

CONCLUSIONS

Evidence supports the use of ketamine for chronic pain, but the level of evidence varies by condition and dose range. Most studies evaluating the efficacy of ketamine were small and uncontrolled and were either unblinded or ineffectively blinded. Adverse effects were few and the rate of serious adverse effects was similar to placebo in most studies, with higher dosages and more frequent infusions associated with greater risks. Larger studies, evaluating a wider variety of conditions, are needed to better quantify efficacy, improve patient selection, refine the therapeutic dose range, determine the effectiveness of nonintravenous ketamine alternatives, and develop a greater understanding of the long-term risks of repeated treatments.

Principles of designing a clinical trial: optimizing chances of trial success

PURPOSE OF REVIEW

Clinical trials are essential to advance health care and develop new therapies. In this review we discuss the underlying principles of clinical trial design with an emphasis on assessing design risks that lead to trial failure as well as negative trials. While of general interest, this is perhaps particularly timely for the neuromodulation community, given the paucity of well-designed trials in the field. We give some examples from the phantom limb pain (PLP) literature.

RECENT FINDINGS

It is critical to gather as much preliminary data as possible and to know how to interpret it in order to choose an appropriate trial design. Therefore, the investigator needs to effectively assess the likely trial design risk/benefit ratio with a view to maximizing the chance of a meaningful outcome, whether this outcome rejects or fails to reject the null hypothesis. This analysis is especially important in a complex and heterogeneous disorder such as PLP, which has had many negative trials.

SUMMARY

We discuss the factors pertaining to a strong trial design benefit/risk assessment, how late trial phases require greater support from preliminary data, how to design trials to minimize risks, maximize benefits, and optimize internal validity as well as the chances of a positive outcome. We highlight the need for investigators to incorporate best practice in trial design to increase the chances of success, to always anticipate unexpected challenges during the trial.

Phantom phenomena in limb amputees – a review article

Amputation leading to the loss of a body part is associated not only with significant economic costs, but also serious consequences of medical and socio-psychological nature. It is the ultimate means to save a life or improve its quality. The most difficult challenges faced by amputees include accepting changes regarding their own physiognomy and the resulting life restrictions. The patient subjected to amputation is faced with an extremely difficult adaptation process, during which s/he should strive for a maximum degree of independence. Unfortunately, a large group of patients also struggles with various types of sensations and pain located within the lost limb − i.e., so-called phantom phenomena. This is a special group of phenomena of diverse nature, “located” within the lost limb. The occurrence of phantom limb syndrome in amputee patients is extremely common. This problem affects from 45% to even 98% of patients after amputation of one or both upper and lower limbs. The main purpose of this article is to describe phantom phenomena observed in patients after limb amputation in light of current literature. The definition, historical outline, types of phantom phenomena are presented, as well as hypothetical pathomechanisms, factors influencing the frequency and intensity of phantom phenomena and available treatment methods. The work was based on numerous text sources and the author’s own experience.

Phantom limb pain: a review of pharmacological management

Introduction

Phantom limb pain (PLP) is a complex condition resulting in pain in the missing limb affecting 60-80% amputees. Increasing number of patients are undergoing amputations. Approximately 1 per every 1000 people in the United Kingdom is an amputee. Incidence of PLP can be as high as 80% following amputation. PLP can be severe and difficult to treat. A range of pharmacological interventions exist yet little is known about them in respect to PLP. This article will address the effectiveness of both single pharmacological, therapy as well as drug combination therapy.

Methods

We reviewed all literature looking at the evidence for the efficacy of both single and combined pharmacological therapy in the management of phantom limb pain. Not all commonly prescribed analgesic agents have been studied in the use of PLP and in these cases, the evidence of their efficacy in neuropathic pain was reviewed.

Conclusion

It is difficult to draw definitive conclusions on the pharmacological management of PLP based on current available evidence. Most trials involved small cohorts and were not specific to the PLP. The trials which looked specifically at the PLP population gave conflicting results. Only the N-methyl-d-aspartate (NMDA) receptor antagonist class demonstrated consistent positive results. Most notably ketamine did produce a reduction in pressure pain thresholds and pain windup associated with PLP, although the numbers in these studies remain small. This benefit was not demonstrated across all NMDA receptor antagonists. Combination therapy has demonstrated effectiveness in previous studies for neuropathic pain but this has never been tested specifically against a PLP cohort. Therefore, combination treatment of agents with proven efficacy in PLP such as opioid and gabapentin deserves a closer examination in a controlled study against a placebo as well as single drug therapy.

Perioperative Pain Management Strategies for Amputation: A Topical Review

Objective

To review acute pain management strategies in patients undergoing amputation with consideration of preoperative patient factors, pharmacologic/interventional modalities, and multidisciplinary care models to alleviate suffering in the immediate post-amputation setting.

Background

Regardless of surgical indication, patients undergoing amputation suffer from significant residual limb pain and phantom limb pain in the acute postoperative phase. Most studies have primarily focused on strategies to prevent persistent pain with inclusion of immediate postoperative outcomes as secondary measures. Pharmacologic agents, including gabapentin, ketamine, and calcitonin, and interventional modalities such as neuraxial and perineural catheters, have been examined in the perioperative period.

Design

Focused Literature Review.

Results

Pharmacologic agents (gabapentin, ketamine, calcitonin) have not shown consistent efficacy. Neuraxial analgesia has demonstrated both an opioid sparing and analgesic benefit while results have been mixed regarding perineural catheters in the immediate post-amputation setting. However, several early studies of perineural catheters employed sub-optimal techniques (distal surgical placement), and prolonged use of perineural catheters may provide a sustained benefit. Regardless of analgesic technique, a multidisciplinary approach is necessary for optimal care.

Conclusion

Patient-tailored analgesic regimens utilizing catheter-based techniques are essential in the acute post-amputation phase and should be implemented in all patients undergoing amputation. Future research should focus on improved measurement of acute pain and comparisons of effective analgesic regimens instead of single techniques.

Systematic review of management of chronic pain after surgery

BACKGROUND

Pain present for at least 3 months after a surgical procedure is considered chronic postsurgical pain (CPSP) and affects 10-50 per cent of patients. Interventions for CPSP may focus on the underlying condition that indicated surgery, the aetiology of new-onset pain or be multifactorial in recognition of the diverse causes of this pain. The aim of this systematic review was to identify RCTs of interventions for the management of CPSP, and synthesize data across treatment type to estimate their effectiveness and safety.

METHODS

MEDLINE, Embase, PsycINFO, CINAHL and the Cochrane Library were searched from inception to March 2016. Trials of pain interventions received by patients at 3 months or more after surgery were included. Risk of bias was assessed using the Cochrane risk-of-bias tool.

RESULTS

Some 66 trials with data from 3149 participants were included. Most trials included patients with chronic pain after spinal surgery (25 trials) or phantom limb pain (21 trials). Interventions were predominantly pharmacological, including antiepileptics, capsaicin, epidural steroid injections, local anaesthetic, neurotoxins, N-methyl-d-aspartate receptor antagonists and opioids. Other interventions included acupuncture, exercise, postamputation limb liner, spinal cord stimulation, further surgery, laser therapy, magnetic stimulation, mindfulness-based stress reduction, mirror therapy and sensory discrimination training. Opportunities for meta-analysis were limited by heterogeneity. For all interventions, there was insufficient evidence to draw conclusions on effectiveness.

CONCLUSION

There is a need for more evidence about interventions for CPSP. High-quality trials of multimodal interventions matched to pain characteristics are needed to provide robust evidence to guide management of CPSP.

A review of the management of phantom limb pain: challenges and solutions

BACKGROUND

Phantom limb pain (PLP) occurs in 50% and 80% of amputees. Although it is often classified as a neuropathic pain, few of the large-scale trials of treatments for neuropathic pain included sufficient numbers of PLP sufferers to have confidence that they are effective in this condition. Many therapies have been administered to amputees with PLP over the years; however, as of yet, there appears to be no first-line treatment.

OBJECTIVES

To comprehensively review the literature on treatment modalities for PLP and to identify the challenges currently faced by clinicians dealing with this pain.

METHOD

MEDLINE, EMBASE, CINAHL, British Nursing Index, Cochrane and psycINFO databases were searched using "Phantom limb" initially as a MeSH term to identify treatments that had been tried. Then, a secondary search combining phantom limb with each treatment was performed to find papers specific to each therapy. Each paper was assessed for its research strength using the GRADE system.

RESULTS

Thirty-eight therapies were identified. Overall, the quality of evidence was low. There was one high-quality study which used repetitive transcutaneous magnetic stimulation and found a statistical reduction in pain at day 15 but no difference at day 30. Significant results from single studies of moderate level quality were available for gabapentin, ketamine and morphine; however, there was a risk of bias in these papers. Mirror therapy and associated techniques were assessed through two systematic reviews, which conclude that there is insufficient evidence to support their use.

CONCLUSION

No decisions can be made for the first-line management of PLP, as the level of evidence is too low. Robust studies on homogeneous populations, an understanding of what amputees consider a meaningful reduction in PLP and agreement of whether pain intensity is the legitimate therapeutic target are urgently required.

Ketamine-A Narrative Review of Its Uses in Medicine

One of the most fascinating drugs in the anesthesiologist's armament is ketamine, an N-methyl-D-aspartate receptor antagonist with a myriad of uses. The drug is a dissociative anesthetic and has been used more often as an analgesic in numerous hospital units, outpatient pain clinics, and in the prehospital realm. It has been used to treat postoperative pain, chronic pain, complex regional pain syndrome, phantom limb pain, and other neuropathic conditions requiring analgesia. Research has also demonstrated its efficacy as an adjunct in psychotherapy, as a treatment for both depression and posttraumatic stress disorder, as a procedural sedative, and as a treatment for respiratory and neurologic conditions. Ketamine is not without its adverse effects, some of which can be mitigated with certain efforts. Such effects make it necessary for the clinician to use the drug only in situations where it will provide the greatest benefit with the fewest adverse effects. To the best of our knowledge, none of the reviews regarding ketamine have taken a comprehensive look at the drug's uses in all territories of medicine. This review will serve to touch on its chemical data, pharmacokinetics and pharmacodynamics, medical uses, and adverse effects while focusing specifically on the drugs usage in anesthesia and analgesia.

Hyperalgesia and Persistent Pain after Breast Cancer Surgery: A Prospective Randomized Controlled Trial with Perioperative COX-2 Inhibition

Background

Persistent pain is a challenging clinical problem after breast cancer treatment. After surgery, inflammatory pain and nociceptive input from nerve injury induce central sensitization which may play a role in the genesis of persistent pain. Using quantitative sensory testing, we tested the hypothesis that adding COX-2 inhibition to standard treatment reduces hyperalgesia after breast cancer surgery. A secondary hypothesis was that patients developing persistent pain would exhibit more postoperative hyperalgesia.

Methods

138 women scheduled for lumpectomy/mastectomy under general anesthesia with paravertebral block were randomized to COX-2 inhibition (2x40mg parecoxib on day of surgery, thereafter 2x200mg celecoxib/day until day five) or placebo. Preoperatively and 1, 5, 15 days and 1, 3, 6, 12 months postoperatively, we determined electric and pressure pain tolerance thresholds in dermatomes C6/T4/L1 and a 100mm VAS score for pain. We calculated the sum of pain tolerance thresholds and analyzed change in these versus preoperatively using mixed models analysis with factor medication. To assess hyperalgesia in persistent pain patients we performed an additional analysis on patients reporting VAS>30 at 12 months.

Results

48 COX-2 inhibition and 46 placebo patients were analyzed in a modified intention to treat analysis. Contrary to our primary hypothesis, change in the sum of tolerance thresholds in the COX-2 inhibition group was not different versus placebo. COX-2 inhibition had an effect on pain on movement at postoperative day 5 (p<0.01). Consistent with our secondary hypothesis, change in sum of pressure pain tolerance thresholds in 11 patients that developed persistent pain was negative versus patients without pain (p<0.01) from day 5 to 1 year postoperatively.

Conclusions

Perioperative COX-2 inhibition has limited value in preventing sensitization and persistent pain after breast cancer surgery. Central sensitization may play a role in the genesis of persistent postsurgical pain.

Pharmacologic interventions for treating phantom limb pain

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 12, 2011. Phantom limb pain (PLP) is pain that arises in the missing limb after amputation and can be severe, intractable, and disabling. Various medications have been studied in the treatment of phantom pain. There is currently uncertainty in the optimal pharmacologic management of PLP.

OBJECTIVES

This review aimed to summarise the evidence of effectiveness of pharmacologic interventions in treating PLP.

SEARCH METHODS

For this update, we searched the Cochrane Central Register of Controlled Trials (CENTRAL, the Cochrane Library), MEDLINE, and Embase for relevant studies. We ran the searches for the original review in September 2011 and subsequent searches for this update up to April 2016. We sought additional studies from clinical trials databases and reference lists of retrieved papers.

SELECTION CRITERIA

We included randomised and quasi-randomised trials studying the effectiveness of pharmacologic interventions compared with placebo, another active treatment, or no treatment, in established PLP. We considered the following outcomes: change in pain intensity, function, sleep, depression or mood, quality of life, adverse events, treatment satisfaction, and withdrawals from the study.

DATA COLLECTION AND ANALYSIS

We independently assessed issues of study quality and extracted efficacy and adverse event data. Due to the wide variability in the studies, we did not perform a meta-analysis for all the interventions and outcomes, but attempted to pool the results of some studies where possible. We prepared a qualitative description and narrative summary of results. We assessed clinical heterogeneity by making qualitative comparisons of the populations, interventions, outcomes/outcome measures, and methods.

MAIN RESULTS

We added only one new study with 14 participants to this updated review. We included a 14 studies (10 with low risk of bias and 4 with unclear risk of bias overall) with a total of 269 participants. We added another drug class, botulinum neurotoxins (BoNTs), in particular botulinum toxin A (BoNT/A), to the group of medications reviewed previously. Our primary outcome was change in pain intensity. Most studies did not report our secondary outcomes of sleep, depression or mood, quality of life, treatment satisfaction, or withdrawals from the study.BoNT/A did not improve phantom limb pain intensity during the six months of follow-up compared with lidocaine/methylprednisolone.Compared with placebo, morphine (oral and intravenous) was effective in decreasing pain intensity in the short term with reported adverse events being constipation, sedation, tiredness, dizziness, sweating, voiding difficulty, vertigo, itching, and respiratory problems.The N-methyl D-aspartate (NMDA) receptor antagonists ketamine (versus placebo; versus calcitonin) and dextromethorphan (versus placebo), but not memantine, had analgesic effects. The adverse events of ketamine were more serious than placebo and calcitonin and included loss of consciousness, sedation, hallucinations, hearing and position impairment, and insobriety.The results for gabapentin in terms of pain relief were conflicting, but combining the results favoured treatment group (gabapentin) over control group (placebo) (mean difference -1.16, 95% confidence interval -1.94 to -0.38; 2 studies). However, gabapentin did not improve function, depression score, or sleep quality. Adverse events experienced were somnolence, dizziness, headache, and nausea.Compared with an active control benztropine mesylate, amitriptyline was not effective in PLP, with dry mouth and dizziness as the most frequent adverse events based on one study.The findings for calcitonin (versus placebo; versus ketamine) and local anaesthetics (versus placebo) were variable. Adverse events of calcitonin were headache, vertigo, drowsiness, nausea, vomiting, and hot and cold flushes. Most of the studies were limited by their small sample sizes.

AUTHORS' CONCLUSIONS

Since the last version of this review, we identified another study that added another form of medical therapy, BoNTs, specifically BoNT/A, to the list of pharmacologic interventions being reviewed for clinical efficacy in phantom limb pain. However, the results of this study did not substantially change the main conclusions. The short- and long-term effectiveness of BoNT/A, opioids, NMDA receptor antagonists, anticonvulsants, antidepressants, calcitonins, and local anaesthetics for clinically relevant outcomes including pain, function, mood, sleep, quality of life, treatment satisfaction, and adverse events remain unclear. Based on a small study, BoNT/A (versus lidocaine/methylprednisolone) does not decrease phantom limb pain. Morphine, gabapentin, and ketamine demonstrate favourable short-term analgesic efficacy compared with placebo. Memantine and amitriptyline may not be effective for PLP. However, results must be interpreted with caution, as they were based mostly on a small number of studies with limited sample sizes that varied considerably and also lacked long-term efficacy and safety outcomes. The direction of efficacy of calcitonin, local anaesthetics, and dextromethorphan needs further clarification. Overall, the efficacy evidence for the reviewed medications is thus far inconclusive. Larger and more rigorous randomised controlled trials are needed for us to reach more definitive conclusions about which medications would be useful for clinical practice.

The role of ketamine in the treatment of chronic cancer pain

Background and aim

Ketamine is a drug used for the induction and maintenance of general anesthesia, for the treatment of postoperative and posttraumatic acute pain, and more recently, for the reduction of postoperative opioid requirements. The main mechanism of action of ketamine is the antagonization of N-methyl-D-aspartate (NMDA) receptors that are associated with central sensitization. In the pathogenesis of chronic pain and particularly in neuropathic pain, an important role is played by the activation of NMDA receptors. Although ketamine is indicated and used for the treatment of chronic cancer pain as an adjuvant to opioids, there are few clinical studies that clearly demonstrate the effectiveness of ketamine in this type of pain.

The aim of this study is to analyze evidence-based clinical data on the effectiveness and safety of ketamine administration in the treatment of chronic neoplastic pain, and to summarize the evidence-based recommendations for the use of ketamine in the treatment of chronic cancer pain.

Method

We reviewed the literature from the electronic databases of MEDLINE, COCHRANE, PUBMED, MEDSCAPE (1998–2014), as well as chapters of specialized books (palliative care, pain management, anesthesia).

Results

A number of studies support the effectiveness of ketamine in the treatment of chronic cancer pain, one study does not evidence clear clinical benefits for the use of ketamine, and some studies included too few patients to be conclusive.

Conclusions

Ketamine represents an option for neoplasic pain that no longer responds to conventional opioid treatment, but this drug should be used with caution, and the development of potential side effects should be carefully monitored.