Pharmacologic interventions for treating phantom limb pain

Efficacy and Safety of Antidepressants in Patients With Comorbid Depression and Medical Diseases: An Umbrella Systematic Review and Meta-Analysis

Importance

Every third to sixth patient with medical diseases receives antidepressants, but regulatory trials typically exclude comorbid medical diseases. Meta-analyses of antidepressants have shown small to medium effect sizes, but generalizability to clinical settings is unclear, where medical comorbidity is highly prevalent.

Objective

To perform an umbrella systematic review of the meta-analytic evidence and meta-analysis of the efficacy and safety of antidepressant use in populations with medical diseases and comorbid depression.

Data Sources

PubMed and EMBASE were searched from inception until March 31, 2023, for systematic reviews with or without meta-analyses of randomized clinical trials (RCTs) examining the efficacy and safety of antidepressants for treatment or prevention of comorbid depression in any medical disease.

Study Selection

Meta-analyses of placebo- or active-controlled RCTs studying antidepressants for depression in individuals with medical diseases.

Data Extraction and Synthesis

Data extraction and quality assessment using A Measurement Tool for the Assessment of Multiple Systematic Reviews (AMSTAR-2 and AMSTAR-Content) were performed by pairs of independent reviewers following PRISMA guidelines. When several meta-analyses studied the same medical disease, the largest meta-analysis was included. Random-effects meta-analyses pooled data on the primary outcome (efficacy), key secondary outcomes (acceptability and tolerability), and additional secondary outcomes (response and remission).

Main Outcomes and Measures

Antidepressant efficacy presented as standardized mean differences (SMDs) and tolerability (discontinuation for adverse effects) and acceptability (all-cause discontinuation) presented as risk ratios (RRs).

Results

Of 6587 references, 176 systematic reviews were identified in 43 medical diseases. Altogether, 52 meta-analyses in 27 medical diseases were included in the evidence synthesis (mean [SD] AMSTAR-2 quality score, 9.3 [3.1], with a maximum possible of 16; mean [SD] AMSTAR-Content score, 2.4 [1.9], with a maximum possible of 9). Across medical diseases (23 meta-analyses), antidepressants improved depression vs placebo (SMD, 0.42 [95% CI, 0.30-0.54]; I2 = 76.5%), with the largest SMDs for myocardial infarction (SMD, 1.38 [95% CI, 0.82-1.93]), functional chest pain (SMD, 0.87 [95% CI, 0.08-1.67]), and coronary artery disease (SMD, 0.83 [95% CI, 0.32-1.33]) and the smallest for low back pain (SMD, 0.06 [95% CI, 0.17-0.39]) and traumatic brain injury (SMD, 0.08 [95% CI, -0.28 to 0.45]). Antidepressants showed worse acceptability (24 meta-analyses; RR, 1.17 [95% CI, 1.02-1.32]) and tolerability (18 meta-analyses; RR, 1.39 [95% CI, 1.13-1.64]) compared with placebo. Antidepressants led to higher rates of response (8 meta-analyses; RR, 1.54 [95% CI, 1.14-1.94]) and remission (6 meta-analyses; RR, 1.43 [95% CI, 1.25-1.61]) than placebo. Antidepressants more likely prevented depression than placebo (7 meta-analyses; RR, 0.43 [95% CI, 0.33-0.53]).

Conclusions and Relevance

The results of this umbrella systematic review of meta-analyses found that antidepressants are effective and safe in treating and preventing depression in patients with comorbid medical disease. However, few large, high-quality RCTs exist in most medical diseases.

High-dose opioids for chronic non-cancer pain: an overview of Cochrane Reviews

BACKGROUND

This overview was originally published in 2017, and is being updated in 2022.  Chronic pain is typically described as pain on most days for at least three months. Chronic non-cancer pain (CNCP) is any chronic pain that is not due to a malignancy. Chronic non-cancer pain in adults is a common and complex clinical issue, for which opioids are prescribed by some physicians for pain management. There are concerns that the use of high doses of opioids for CNCP lacks evidence of effectiveness, and may increase the risk of adverse events.

OBJECTIVES

To describe the evidence from Cochrane Reviews and overviews regarding the efficacy and safety of high-dose opioids (defined as 200 mg morphine equivalent or more per day) for CNCP.

METHODS

We identified Cochrane Reviews and overviews by searching the Cochrane Database of Systematic Reviews in The Cochrane Library. The date of the last search was 21 July 2022. Two overview authors independently assessed the search results. We planned to analyse data on any opioid agent used at a high dose for two weeks or more for the treatment of CNCP in adults.

MAIN RESULTS

We did not identify any reviews or overviews that met the inclusion criteria. The excluded reviews largely reflected low doses or titrated doses, where all doses were analysed as a single group; we were unable to extract any data for high-dose use only.

AUTHORS' CONCLUSIONS

There is a critical lack of high-quality evidence, in the form of Cochrane Reviews, about how well high-dose opioids work for the management of CNCP in adults, and regarding the presence and severity of adverse events.  No evidence-based argument can be made on the use of high-dose opioids, i.e. 200 mg morphine equivalent or more daily, in clinical practice. Considering that high-dose opioids have been, and are still being used in clinical practice to treat CNCP, knowing about the efficacy and safety of these higher doses is imperative.

Effect of a continuous perineural levobupivacaine infusion on pain after major lower limb amputation: a randomised double-blind placebo-controlled trial

OBJECTIVES

Randomised controlled trial of the effect of a perineural infusion of levobupivacaine on moderate/severe phantom limb pain 6 months after major lower limb amputation.

SETTING

Single-centre, UK university hospital.

PARTICIPANTS

Ninety patients undergoing above-knee and below-knee amputation for chronic limb threatening ischaemia under general anaesthesia. Exclusion criteria were patients having surgery under neuraxial anaesthesia; inability to operate a patient-controlled analgesia device or complete a Visual Analogue Scale; amputation for trauma or malignancy; or contraindication to levobupivacaine.

INTERVENTIONS

Either levobupivacaine 0.125% or saline 0.9% (10 mL bolus, infusion of 8 mL/hour for 96 hours) via a sciatic or posterior tibial nerve sheath catheter placed under direct vision during surgery.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was the presence of phantom limb pain, residual limb pain and phantom limb sensations up to 6 months after amputation. Secondary outcome measures included early postoperative pain and morphine requirements after surgery.

RESULTS

Data from 81 participants were analysed; 6-month follow-up data were available for 62 patients. Pain and morphine requirements varied widely before and after amputation in both groups. The incidences of moderate/severe phantom limb pain, residual limb pain and phantom limb sensations were low from 6 weeks with no significant differences between groups in phantom limb pain at rest (OR 0.56, 95% CI 0.14 to 2.14, p=0.394) or movement (OR 0.58, 95% CI 0.15 to 2.21, p=0.425) at 6 months. Early postoperative pain scores were low in both groups with no between-group differences in residual limb pain or phantom limb sensations (rest or movement) at any time point. High postoperative morphine consumption was associated with worsening phantom limb pain both at rest (-17.51, 95% CI -24.29 to -10.74; p<0.001) and on movement (-18.54, 95% CI -25.58 to -11.49; p<0.001). The incidence of adverse effects related to the study was low in both groups: postoperative nausea, vomiting and sedation scores were similar, and there were no features of local anaesthetic toxicity.

CONCLUSIONS

Long-term phantom limb pain, residual limb pain and phantom limb sensations were not reduced significantly by perineural infusion of levobupivacaine, although the study was underpowered to show significant differences in the primary outcome. The incidence of phantom limb pain was lower than previously reported, possibly attributable to frequent assessment and early intervention to identify and treat postoperative pain when it occurred. There were large variations in postoperative pain scores, high requirements for analgesics before and after surgery and some problems maintaining recruitment and long -term follow-up. Knowledge of these potential problems should inform future research in this group of patients. Further work should investigate the association between perioperative morphine requirements and late phantom limb pain.

TRIAL REGISTRATION NUMBERS

EudraCT 2007-000619-27; ISRCTN68691928.

Advances in Oncoanaesthesia and Cancer Pain

INTRODUCTION

The growing interest on how peri-‑operative interventions, especially regional anesthesia, during cancer surgery can alter oncological outcome increasing disease free survival is probably responsible for the birth of the new subspecialty called onco-anesthesia. A paradigm shift in the concept of anesthetic management has occurred recently owing to the innumerable diverse revelations from the ongoing research in this field.

DISCUSSION

Long lasting but reversible epigenetic changes can occur due to surgical stress and perioperative anesthetic medications. The exact relationship between these factors and tumor biology is being studied further. A popular topic under research now is the influence of regional anesthesia on cancer recurrence. Combining nerve blocks with total intravenous anesthesia (TIVA) brings down the requirement of opioids and volatile anesthetic agents implicated in cancer recurrence. The study of mechanism of pain at the molecular level has led to the discovery of novel modes of prevention of chronic post-surgical pain. Newer combination aggressive treatment therapies -intraoperative chemotherapy and radiotherapy, isolated limb perfusion, photodynamic therapy and robotic surgery require specialized anesthetic management. The COVID pandemic introduced new guidelines for safe management of oncosurgical patients .Use of genomic mapping to personalize pain management will be the breakthrough of the decade.

CONCLUSION

The discovery that anesthetic strategy could have significant oncological sequel is a quantum leap forward. Avoiding some anesthetic medications may decrease cancer recurrence. Comprehensive cancer care and translational research will pave the way to uncover safe anesthetic practices.

Clonazepam: An Old "New" Therapy for the Treatment of Phantom Limb Pain-A Brief Report of a Retrospective Study

The purpose of this study is to describe the results of clonazepam use in the treatment of phantom limb pain (PLP). Although the efficacy of clonazepam on PLP has been reported in 1996, there are no subsequent known studies that confirmed this report. A consecutive sample of 32 patients who suffered from PLP after recent lower limb amputation was studied based on clinical charts. Wilcoxon's signed rank test was used to compare Numeric Rating Scale (NRS) values before and after the treatment with clonazepam. Twenty-three amputees were treated only with clonazepam, without adding other drugs or targeted rehabilitation treatments. The median NRS before the treatment with clonazepam was 7 (2), the median NRS after 31 ± 5 days of treatment was 3 (3.5) (p < 0.0001). The average dosage of clonazepam used was 1.5 ± 1 mg per day. The results suggest that clonazepam has to be considered as an alternative drug for PLP treatment.

Targeted Muscle Reinnervation for the Treatment of Neuroma

Targeted muscle reinnervation (TMR) is the surgical rerouting of severed nerve endings to nearby expendable motor nerve branches. These nerve transfers provide a pathway for axonal growth, limiting the amputated nerve ends' disorganized attempt at regeneration that leads to neuroma formation. In the amputee population, TMR is successful in the treatment and prevention of chronic phantom limb pain and residual limb pain. In the nonamputee population, applications of TMR are ever expanding in the treatment of chronic neuroma pain owing to trauma, compression, or surgery. This article reviews the indications for TMR, preoperative evaluation, and various surgical techniques.

Phantom eye syndrome. Case report and literature review

A frequent complication after limb amputation is the appearance of phantom limb syndrome, a phenomenon that has also been studied in the amputation of different body parts. Cases reported in relation to ophthalmologic surgery are few and evidence is limited in terms of specific management, which makes this a very important study. We report the case of a patient diagnosed with phantom eye syndrome in the post-operative period of an orbital exenteration surgery. A comprehensive approach was taken with multimodal symptom management, including intervention treatment. Significant improvement regarding the pain was achieved; however, non-painful ghost sensations persisted. Upon reviewing the available literature on the subject, its pathophysiology is not fully elucidated. Its incidence is highly variable, as well as the symptoms’ appearance. The presence of headache and eye pain prior to surgery seem to be risk factors. Climate and psychological stress are exacerbating factors of the symptomatology. No high-quality evidence was found in terms of management guidelines, with the use of antidepressants, anticonvulsants and opioids being the most recommended. Interventional management is an option according to the characteristics of the pain and associated symptoms.

Management of Unreconstructable Saphenous Nerve Injury with Targeted Muscle Reinnervation

Neuroma pain significantly impacts patient quality of life and is associated with unemployment, chronic opioid dependence, and depression. Targeted muscle reinnervation (TMR), a surgical technique that coapts proximal stumps of cut nerves to distal motor nerves of adjacent muscles, has demonstrated efficacy in the treatment and prevention of neuroma pain. The objective of this study was to describe the surgical technique for TMR of the saphenous nerve, while providing a retrospective review. Between January 2015 and December 2018, 18 patients underwent TMR of the saphenous nerve: 1 nonamputee patient with chronic pain after ankle surgery and 17 amputee patients (10 for relief of chronic postamputation neuroma pain and phantom pain and 7 at the time of amputation for prevention of these symptoms). Six patients were lost to follow up; 2 patients had recurrent pain; and 10 patients had reduced or no pain after TMR surgery. TMR is a successful technique for the management of traumatic neuroma pain in both the amputee and nonamputee populations, and in this study, we describe the technique for saphenous nerve TMR.

Therapeutic Approaches for Peripheral and Central Neuropathic Pain

Neuropathic pain is a chronic secondary pain condition, which is a consequence of peripheral or central nervous (somatosensory) system lesions or diseases. It is a devastating condition, which affects around 7% of the general population. Numerous etiological factors contribute to the development of chronic neuropathic pain. It can originate from the peripheral part of the nervous system such as in the case of trigeminal or postherpetic neuralgia, peripheral nerve injury, painful polyneuropathies, or radiculopathies. Central chronic neuropathic pain can develop as a result of spinal cord or brain injury, stroke, or multiple sclerosis. As first-line pharmacological treatment options, tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and gabapentinoids are recommended. In trigeminal neuralgia, carbamazepine and oxcarbazepine are the first-choice drugs. In drug-refractory cases, interventional, physical, and psychological therapies are available. This review was structured based on a PubMed search of papers published in the field from 2010 until May 2019.

Identification of novel analgesics through a drug repurposing strategy

The identification of new indications for approved or failed drugs is a process called drug repositioning or drug repurposing. The motivation includes overcoming the productivity gap that exists in drug development, which is a high-cost–high-risk process. Repositioning also includes rescuing drugs that have safely entered the market but have failed to demonstrate sufficient efficiency for the initial clinical indication. Considering the high prevalence of chronic pain, the lack of sufficient efficacy and the safety issues of current analgesics, repositioning seems to be an attractive approach. This review presents example of drugs that already have been repositioned and highlights new technologies that are available for the identification of additional compounds to stimulate the curiosity of readers for further exploration.

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.

Possible inflammatory pain biomarkers in postamputation pain

Although chronic pain after amputation is frequent, the underlying mechanisms are still not well understood. It is widely accepted that the pathogenesis of postamputation pain is multifactorial, with both peripheral and central mechanisms playing an essential role. However, recent studies suggest that the immune system plays an important role in different neuropathic pain conditions, including postamputation pain. Eleven amputees were included in this clinical study. Information on the type and intensity of spontaneous postamputation pain was obtained and evoked pain responses for brush, cold, and warm allodynia and pinprick hyperalgesia were determined. In addition, skin biopsies were taken from the amputated site and a contralateral control site and analysed for possible markers of pain: IbA1 (macrophages), calcitonin gene-related peptide (CGRP), and substance P (SP). Irrespectively of the type and intensity of postamputation pain, no differences were found in IbA1, CGRP, and SP levels between the amputated site and the control site. Although no differences between the sites were seen in this study, this new method seems promising for our understanding of skin changes in amputees. In future studies, staining for other cytokines and inflammatory mediators in skin biopsies could provide new insight into the mechanisms of postamputation pain.

The prevalence of phantom limb pain and associated risk factors in people with amputations: a systematic review protocol

BACKGROUND

The prevalence of phantom limb pain (PLP) in people with amputations is unclear because of the conflicting reports across the literature. It is proposed that the conflicting reports on the prevalence of PLP are a consequence of variations in the time period during which the studies were undertaken, countries in which the studies were conducted and recruitment processes implemented during collection of epidemiological data. In consideration of these factors, we aim to gather and critically appraise relevant literature to determine the prevalence estimate of and risk factors for PLP in people with amputations.

METHODS

We will use a customised search strategy containing relevant words and terms to search the following databases: MEDLINE/PubMed (via EBSCOhost), PsycINFO (via EBSCOhost), PsycArticles, Cumulative Index to Nursing and Allied Health Literature (CINAHL) (via EBSCOhost), Africa-Wide Information (via EBSCOhost), Health Source: Nursing/Academic Edition (via EBSCOhost) SCOPUS, Web of Science and Academic Search Premier (via EBSCOhost). The risk of bias assessment will be conducted using a risk of bias assessment tool for prevalence studies, and data will be extracted using a piloted customised data extraction sheet. Data extracted from individual studies will be entered into Review Manager 5 and assessed for clinical and statistical heterogeneity. Studies will be pooled for meta-analysis using the random-effects model to determine a summary estimate of the prevalence of PLP across included studies. A statistically significant level will be set at p < 0.05.

DISCUSSION

As far as we know, a systematic review and meta-analysis on the prevalence of, and risk factors for PLP in people with amputations has not been conducted. Given the varying reports in the literature, it is necessary to determine an estimate of the prevalence of PLP to generate an informed conclusion on this subject. The results of this review will be published in an internationally accredited journal and used to inform researchers, clinicians, policy-makers and the public about the burden of, and risk factors for PLP. This will be done with a further aim to improve the quality of pain management in society.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42018094821.

Can phantom limb pain be reduced/eliminated solely by techniques applied to peripheral nerves?

About 0.5% of the US population (1.7 million) is living with a lost limb and this number is expected to double by 2050. This number is much higher in other parts of the world. Within days to weeks of an extremity amputation, up to 80% of these individuals develop neuropathic pain presenting as phantom limb pain (PLP). The level of PLP increases significantly by one year and remains chronic and severe for about 10% of individuals. PLP has a serious negative impact on individuals’ lives. Current pain treatment therapies, such pharmacological approaches provide limited to no pain relief, some other techniques applied to the central nervous system (CNS) and peripheral nervous system (PNS) reduce or block PLP, but none produces long-term pain suppression. Therefore, new drugs or novel analgesic methods must be developed that prevent PLP from developing, or if it develops, to reduce the level of pain. This paper examines the potential causes of PLP, and present techniques used to prevent the development of PLP, or if it develops, to reduce the level of pain. Finally it presents a novel technique being developed that eliminates/reduces chronic neuropathic pain and which may induce the long-term reduction/elimination of PLP.

Major lower limb amputation audit - introduction and implementation of a multimodal perioperative pain management guideline

Lower limb amputation is a frequent surgical intervention. It is well known to be associated with postoperative pain. Optimisation of perioperative pain has been shown to reduce the risk of chronic pain. There are no national guidelines for the perioperative pain management of lower limb amputations. Following a baseline audit, we devised a multimodal perioperative pain management guideline, which included the insertion of a local anaesthetic perineural catheter. All patients undergoing an elective or emergency above, through and below knee amputation were reviewed prior and following the implementation of this guideline. Patient postoperative pain scores and opiate usage were analysed. One hundred and twenty-four patients were reviewed (68 patients prior to the implementation of the guideline and 56 patients following the guideline introduction). Following the implementation of the guideline, a greater proportion of patient's pain scores were reported as 0 (i.e. no pain) compared to patients prior to its implementation (78% vs 61%). Pain scores were lower at all time intervals 6 days postoperatively following the guideline introduction. Statistically significant (Kendall's tau-b analysis) (p < 0.05) reduction in pain scores was found upon admission to the ward, 6, 12, 24 hours and 2 days postoperatively. Fewer patients required the use of opioid patient controlled of analgesia after the guideline was introduced (26% vs 4%). The implementation of a perioperative pain management guideline improved pain scores and reduced opioid consumption in patients undergoing lower limb amputations. We suggest a holistic and collaborative, multimodal pathway towards the perioperative pain management of lower limb amputations.

[Ultrasound-guided interventions on the peripheral nervous system]

CLINICAL/METHODICAL ISSUE

Up to the advent of high-resolution ultrasound, interventions on the peripheral nervous system, including local anesthesia and pain treatment were performed without visual guidance, which in some cases led to treatment failure or local tissue and nerve damage.

METHODICAL INNOVATIONS

Progress in the field of ultrasound has enabled the functional visualization, anesthesia and anti-inflammatory or neurolytic treatment of many peripheral nerves, such as the brachial plexus, nerves of the upper and lower extremities and various nerves of the trunk. Contrast medium-guided biopsies have also become feasible.

ACHIEVEMENTS

This article discusses the general prerequisites for such interventions and details the visualization and the interventional algorithms for interventions on the brachial plexus, on large nerves often affected by compression neuropathies, such as the median, ulnar, sciatic and femoral nerves and small nerves, such as the lateral cutaneous nerves of the thigh. Furthermore, contrast medium-aided biopsies of intraneural and perineural masses are discussed. Finally, the treatment of stump neuromas via phenol instillation is described.

PRACTICAL RECOMMENDATIONS

Innovations in high-resolution ultrasound allow the reliable and safe diagnosis and treatment of various pathologies of the peripheral nervous system with few side effects. Compared to older methods, which did not use visual guidance ultrasound provides higher success rates and lower adverse event rates in many instances.

Sport-Specific Limb Prostheses in Para Sport

Prostheses form an essential part of participation in sport and physical activity for athletes with lower or upper limb amputation. These prostheses come in the form of everyday nonsport-specific prostheses, as well as sport-specific prostheses designed to enable participation in specific sports. Sport-specific prostheses are designed to the requirements of the sport to facilitate the achievement of peak performance without causing significant risk of injury. This article addresses the various factors associated with participation in sport and physical activity for individuals with amputation, including the various prostheses for upper and lower limbs and prostheses for different sports.

The Involvement of the Endocannabinoid System in the Peripheral Antinociceptive Action of Ketamine

Ketamine has been widely used as an analgesic and produces dissociative anesthetic effects. The antinociceptive effects of ketamine have been studied, but the involvement of endocannabinoids in these effects has not yet been investigated. In this study, we evaluated the involvement of the endocannabinoid system in the peripheral antinociceptive effects induced by ketamine. All drugs were administered via the intraplantar route. To induce hyperalgesia, rat paws were injected with prostaglandin E₂ (2 µg per paw). The nociceptive threshold for mechanical stimulation was measured in the right hind paw of Wistar rats using the Randall-Selitto test. The tissue levels of anandamide (AEA), 2-arachidonoylglycerol, palmitoylethanolamide, and oleoylethanolamide were measured using liquid chromatography coupled to single quadrupole mass spectrometry. The administration of the cannabinoid receptor type 1 (CB₁) antagonist, N(piperidine-1yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl 1 pyrazolcarboxamide (20, 40, and 80 µg per paw), but not the cannabinoid receptor type 2 antagonist, 6-iodo-2-methyl-1-(2-morpholinoethyl)-1H-indol-3-yl) (4-methoxyphenyl) methanone (100 µg per paw), antagonized the ketamine-induced peripheral antinociception in a dose-dependent manner. Additionally, the administration of the endocannabinoid metabolizing enzyme inhibitor (.5 µg per paw) or an AEA reuptake inhibitor, (5Z,8Z,11Z,14Z)N(4Hydroxy2methylphenyl)5,8,11,14 eicosatetraenamide (2.5 µg per paw) significantly enhanced low-dose ketamine-induced peripheral antinociception. AEA paw levels were increased only after ketamine administration to prostaglandin E₂-injected paws. These data suggest that ketamine, in the presence of a nociceptive stimulus, induces a selective release of AEA levels and subsequent CB₁ cannabinoid activation at the peripheral level.

PERSPECTIVE

This study suggests that ketamine antinociception depends at least in part on AEA release and CB₁ cannabinoid receptor activation in inflammatory conditions. This study could potentially help clinicians in the use of ketamine as a peripheral analgesic for inflammatory pain.

High-dose opioids for chronic non-cancer pain: an overview of Cochrane Reviews

BACKGROUND

Chronic pain is typically described as pain on most days for at least three months. Chronic non-cancer pain (CNCP) is any chronic pain that is not due to a malignancy. Chronic non-cancer pain in adults is a common and complex clinical issue where opioids are routinely used for pain management. There are concerns that the use of high doses of opioids for chronic non-cancer pain lacks evidence of effectiveness and may increase the risk of adverse events.

OBJECTIVES

To describe the evidence from Cochrane Reviews and Overviews regarding the efficacy and safety of high-dose opioids (here defined as 200 mg morphine equivalent or more per day) for chronic non-cancer pain.

METHODS

We identified Cochrane Reviews and Overviews through a search of the Cochrane Database of Systematic Reviews (The Cochrane Library). The date of the last search was 18 April 2017. Two review authors independently assessed the search results. We planned to analyse data on any opioid agent used at high dose for two weeks or more for the treatment of chronic non-cancer pain in adults.

MAIN RESULTS

We did not identify any reviews or overviews meeting the inclusion criteria. The excluded reviews largely reflected low doses or titrated doses where all doses were analysed as a single group; no data for high dose only could be extracted.

AUTHORS' CONCLUSIONS

There is a critical lack of high-quality evidence regarding how well high-dose opioids work for the management of chronic non-cancer pain in adults, and regarding the presence and severity of adverse events. No evidence-based argument can be made on the use of high-dose opioids, i.e. 200 mg morphine equivalent or more daily, in clinical practice. Trials typically used doses below our cut-off; we need to know the efficacy and harm of higher doses, which are often used in clinical practice.

Adverse events associated with medium- and long-term use of opioids for chronic non-cancer pain: an overview of Cochrane Reviews

BACKGROUND

Chronic pain is common and can be challenging to manage. Despite increased utilisation of opioids, the safety and efficacy of long-term use of these compounds for chronic non-cancer pain (CNCP) remains controversial. This overview of Cochrane Reviews complements the overview entitled 'High-dose opioids for chronic non-cancer pain: an overview of Cochrane Reviews'.

OBJECTIVES

To provide an overview of the occurrence and nature of adverse events associated with any opioid agent (any dose, frequency, or route of administration) used on a medium- or long-term basis for the treatment of CNCP in adults.

METHODS

We searched the Cochrane Database of Systematic Reviews (the Cochrane Library) Issue 3, 2017 on 8 March 2017 to identify all Cochrane Reviews of studies of medium- or long-term opioid use (2 weeks or more) for CNCP in adults aged 18 and over. We assessed the quality of the reviews using the AMSTAR criteria (Assessing the Methodological Quality of Systematic Reviews) as adapted for Cochrane Overviews. We assessed the quality of the evidence for the outcomes using the GRADE framework.

MAIN RESULTS

We included a total of 16 reviews in our overview, of which 14 presented unique quantitative data. These 14 Cochrane Reviews investigated 14 different opioid agents that were administered for time periods of two weeks or longer. The longest study was 13 months in duration, with most in the 6- to 16-week range. The quality of the included reviews was high using AMSTAR criteria, with 11 reviews meeting all 10 criteria, and 5 of the reviews meeting 9 out of 10, not scoring a point for either duplicate study selection and data extraction, or searching for articles irrespective of language and publication type. The quality of the evidence for the generic adverse event outcomes according to GRADE ranged from very low to moderate, with risk of bias and imprecision being identified for the following generic adverse event outcomes: any adverse event, any serious adverse event, and withdrawals due to adverse events. A GRADE assessment of the quality of the evidence for specific adverse events led to a downgrading to very low- to moderate-quality evidence due to risk of bias, indirectness, and imprecision.We calculated the equivalent milligrams of morphine per 24 hours for each opioid studied (buprenorphine, codeine, dextropropoxyphene, dihydrocodeine, fentanyl, hydromorphone, levorphanol, methadone, morphine, oxycodone, oxymorphone, tapentadol, tilidine, and tramadol). In the 14 Cochrane Reviews providing unique quantitative data, there were 61 studies with a total of 18,679 randomised participants; 12 of these studies had a cross-over design with two to four arms and a total of 796 participants. Based on the 14 selected Cochrane Reviews, there was a significantly increased risk of experiencing any adverse event with opioids compared to placebo (risk ratio (RR) 1.42, 95% confidence interval (CI) 1.22 to 1.66) as well as with opioids compared to a non-opioid active pharmacological comparator, with a similar risk ratio (RR 1.21, 95% CI 1.10 to 1.33). There was also a significantly increased risk of experiencing a serious adverse event with opioids compared to placebo (RR 2.75, 95% CI 2.06 to 3.67). Furthermore, we found significantly increased risk ratios with opioids compared to placebo for a number of specific adverse events: constipation, dizziness, drowsiness, fatigue, hot flushes, increased sweating, nausea, pruritus, and vomiting.There was no data on any of the following prespecified adverse events of interest in any of the included reviews in this overview of Cochrane Reviews: addiction, cognitive dysfunction, depressive symptoms or mood disturbances, hypogonadism or other endocrine dysfunction, respiratory depression, sexual dysfunction, and sleep apnoea or sleep-disordered breathing. We found no data for adverse events analysed by sex or ethnicity.

AUTHORS' CONCLUSIONS

A number of adverse events, including serious adverse events, are associated with the medium- and long-term use of opioids for CNCP. The absolute event rate for any adverse event with opioids in trials using a placebo as comparison was 78%, with an absolute event rate of 7.5% for any serious adverse event. Based on the adverse events identified, clinically relevant benefit would need to be clearly demonstrated before long-term use could be considered in people with CNCP in clinical practice. A number of adverse events that we would have expected to occur with opioid use were not reported in the included Cochrane Reviews. Going forward, we recommend more rigorous identification and reporting of all adverse events in randomised controlled trials and systematic reviews on opioid therapy. The absence of data for many adverse events represents a serious limitation of the evidence on opioids. We also recommend extending study follow-up, as a latency of onset may exist for some adverse events.

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.

[Psychotherapies for the Treatment of Phantom Limb Pain]

INTRODUCTION

The phantom limb pain has been described as a condition in which patients experience a feeling of itching, spasm or pain in a limb or body part that has been previously amputated. Such pain can be induced by a conflict between the representation of the visual and proprioceptive feedback of the previously healthy limb. The phantom limb pain occurs in at least 42 to 90% of amputees. Regular drug treatment of phantom limb pain is almost never effective.

METHODS

A systematic review of the literature was conducted in Medline and Cochrane using the MESH terms "phantom limb pain" and "psychotherapy", published in the last 10 years, in English and Spanish, finding 49 items. After reviewing the abstracts, 25 articles were excluded for not being related to the objective of the research. Additionally cross references of included articles and literature were reviewed.

OBJECTIVES

To describe the psychotherapies used in the management of phantom limb pain, their effectiveness and clinical application reported in the literature.

AIMS

The mechanisms underlying phantom limb pain were initially explained, as were the published studies on the usefulness of some psychotherapies such as mirror visual feedback and immersive virtual reality, visual imagery, desensitization and reprocessing eye movements and hypnosis.

CONCLUSIONS

The phantom limb pain is a complex syndrome that requires pharmacological and psychotherapeutic intervention. The psychotherapies that have been used the most as adjuvants in the treatment of phantom limb pain are mirror visual feedback, desensitization and reprocessing eye movements, imagery and hypnosis. Studies with more representative samples, specifically randomized trials are required.

A Randomized, Controlled Trial of Mirror Therapy for Upper Extremity Phantom Limb Pain in Male Amputees

Objective

Phantom limb pain (PLP) is prevalent in patients post-amputation and is difficult to treat. We assessed the efficacy of mirror therapy in relieving PLP in unilateral, upper extremity male amputees.

Methods

Fifteen participants from Walter Reed and Brooke Army Medical Centers were randomly assigned to one of two groups: mirror therapy (n = 9) or control (n = 6, covered mirror or mental visualization therapy). Participants were asked to perform 15 min of their assigned therapy daily for 5 days/week for 4 weeks. The primary outcome was pain as measured using a 100-mm Visual Analog Scale.

Results

Subjects in the mirror therapy group had a significant decrease in pain scores, from a mean of 44.1 (SD = 17.0) to 27.5 (SD = 17.2) mm (p = 0.002). In addition, there was a significant decrease in daily time experiencing pain, from a mean of 1,022 (SD = 673) to 448 (SD = 565) minutes (p = 0.003). By contrast, the control group had neither diminished pain (p = 0.65) nor decreased overall time experiencing pain (p = 0.49). A pain decrement response seen by the 10th treatment session was predictive of final efficacy.

Conclusion

These results confirm that mirror therapy is an effective therapy for PLP in unilateral, upper extremity male amputees, reducing both severity and duration of daily episodes.

Registration

NCT0030144 ClinicalTrials.gov.

Acupuncture for the treatment of phantom limb syndrome in lower limb amputees: a randomised controlled feasibility study

Background

Post amputation, the complication of phantom limb pain (PLP) is prevalent and difficult to manage. This study aimed to determine whether it was feasible and acceptable to undertake a definitive multicentred randomised controlled trial assessing the effectiveness of acupuncture for treating lower limb amputees with PLP.

Methods

A mixed-methods embedded design, including a randomised controlled trial and semistructured interviews, was undertaken. A total of 15 participants with PLP were randomly assigned to receive either eight pragmatic Traditional Chinese Medicine acupuncture treatments and usual care or usual care alone over 4 weeks. Outcome measures were completed at baseline, weekly throughout the study and at 1 month post completion of the study and included: a numerical pain-rating scale, the Short-Form McGill Pain Questionnaire 2, the EQ-5D-5 L, the Hospital Anxiety and Depression Scale, the Perceived Stress Scale 10-item, the Insomnia Severity Index, and the Patient Global Impression of Change. Post completion of the trial, participants in the acupuncture group were interviewed about their experience. Feasibility-specific data were also collected.

Results

Of 24 amputees meeting the study inclusion criteria, 15 agreed to participate (recruitment rate 62.50 %). Qualitatively, acupuncture was perceived to be beneficial and effective. Quantitatively, acupuncture demonstrated clinically meaningful change in average pain intensity (raw change = 2.69) and worst pain intensity (raw change = 4.00). Feasibility-specific data identified that before undertaking a definitive trial, recruitment, practitioner adherence to the acupuncture protocol, completion of outcome measures at 1 month follow-up and blinding should be addressed. Appropriate outcome measures were identified for use in a definitive trial. Data were generated for future sample size calculations (effect size 0.64). Allowing for a 20 % dropout rate, a sample size of 85 participants per group would be needed in a future definitive trial.

Conclusions

A future definitive trial may be possible if the areas identified in this study are addressed. As acupuncture may be effective at treating PLP, and as this feasibility study suggests that a definitive trial may be possible, a multicentred trial with adequate sample size and blinding is now needed.

Trial registration

ClinicalTrials.gov Identifier: NCT02126436, registered on 4 September 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1639-z) contains supplementary material, which is available to authorized users.

Self-Reported Cognitive Concerns in People With Lower Limb Loss

OBJECTIVES

To investigate differences between self-reported cognitive concerns in people with lower limb loss (LLL) and normative data derived from the U.S. general population, and secondarily to determine whether there were cognitive differences based on amputation etiology or age.

DESIGN

Survey.

SETTING

General community.

PARTICIPANTS

A volunteer sample of persons with LLL (N=1086) resulting from trauma or dysvascular complications who regularly use a prosthetic limb.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The Quality of Life in Neurological Disorders Applied Cognition-General Concerns Short Form version 1.0 (Neuro-QoL ACGC), an 8-item self-report measure of general cognitive concerns.

RESULTS

People with LLL reported significantly more cognitive concerns than the Quality of Life in Neurological Disorders normative sample. Mean Neuro-QoL ACGC scores were significantly lower than normative values (P<.001) across subgroups defined by age (ie, <40, 40-49, 50-59, 60-69, and 70+ years) and subgroups defined by etiology (ie, traumatic and dysvascular LLL). However, there were no significant differences in cognitive concerns among age subgroups (P=.84) or between the etiology subgroups (P=.58).

CONCLUSIONS

When compared with the Quality of Life in Neurological Disorders normative sample, individuals with LLL report greater concerns with cognitive health. Cognitive concerns were not differentially affected by age or cause of amputation. The presence of cognitive concerns in people with LLL suggests a need to assess perceived cognitive function in order to tailor education and training in prosthetic use and care.

Improving Functional Outcomes for Vascular Amputees Through Use of Mirror Therapy and Elimination of the Effects of Electromagnetic Fields

The objective of this pilot study was to investigate the effectiveness of combining an amputee limb cover to eliminate the effects of electromagnetic fields (i.e., pain) and a Mirror Therapy exercise program to improve functional outcomes for vascular amputees. A cross-sectional repeated-measures design was used with 14 participants with either acute amputations or surgery at least 8 to 24 months previously. The 4-week intervention included the use of an amputee limb cover and mirror therapy exercises each day. The outcome measures were activities of daily living interference (e.g., self-care, walking, car transfer, low chair transfer, sleep), and well-being (e.g., satisfaction, mood, quality of life) at three times (pre- and posttreatment and maintenance). Participants with acute amputations made significant improvements in the areas of self-care, walking, car transfer, sleep, mood, and quality of life, while the subacute participants improved significantly in sleep and satisfaction. A reduction in the time required before prosthetic fitting decreased from 12 weeks to 8 weeks for acute amputees and an improvement in wearing tolerance from 0-2 to 8-12 hours for the subacute amputees were unexpected results suggesting the combined intervention may improves the extent to which amputees can increase participation in their activities of everyday living.

Use of calcitonin in recalcitrant phantom limb pain complicated by heterotopic ossification

BACKGROUND

Phantom limb pain (PLP) is a common complication after amputation, affecting up to 80% of the amputee population. However, only 5% to 10% of amputees have severe PLP impacting daily function. The present report details the management of severe, treatment-resistant PLP in a 72-year-old man with a traumatic left transradial amputation and a comorbid complication of heterotopic ossification (HO).

OBJECTIVE

To describe a case of PLP with HO and the possible role of calcitonin in the treatment of both conditions.

METHODS

A systematic review of the literature regarding the management of PLP.

RESULTS

Seventeen articles that directly addressed PLP were identified; 11 were randomized controlled trials. All involved small samples and follow-up ranged from 6 h to one year, with the majority limited to six weeks.

DISCUSSION

In the present case, medication management was limited by side effects, lack of response and the patient's desire to avoid long-term medication. Investigations revealed HO, which was suspected to envelop the median nerve in the proximal forearm. After several unsuccessful medication trials, the literature was reviewed in search of common variables between HO formation and persistent PLP. Ultimately, the biochemical effects associated with nerve injury were identified to be a possible factor in both HO and PLP development. Calcitonin's proposed mechanisms of action may help to manage HO and PLP at multiple stages of disease development and maintenance. In the present case, a four-week trial of intranasal calcitonin was successful, with pain control lasting at least 18 months.

CONCLUSION

The present case report provided a review of the current literature in PLP pharmacological management and the current understanding of the etiology of PLP and HO, as well as how the two may coexist. It also provided an opportunity to discuss the proposed mechanisms of action of calcitonin in the management of PLP and HO.

Perceptions of phantom limb pain in lower limb amputees and its effect on quality of life: a qualitative study

BACKGROUND

Phantom limb pain (PLP) is a prevalent complication post-amputation. Currently, qualitative literature exploring the experience of PLP in amputees is sparse, and little is known about whether the educational needs of amputees are being met.

OBJECTIVES

To explore lower limb amputees' descriptive lived experiences of PLP, to understand how PLP affects quality of life and to determine whether amputees feel they are provided with adequate information about PLP.

METHODS

A qualitative descriptive approach, situated under the constructivist paradigm was taken, consisting of cross-sectional semi-structured interviews. A purposive sample of 15 lower limb amputees, 1-3 months post-surgery with past or current experience of PLP were interviewed once about their experience of PLP. Interviews were audio-recorded, transcribed verbatim and analysed using Framework Analysis. Interviews were conducted while participants were inpatients at an amputee rehabilitation unit in London.

RESULTS

Six key themes were identified during analysis, of which three were related to PLP and are reported on in this article (real and physical phantoms, living with a phantom and being informed). PLP had numerous painful qualities. The phantom felt real, with kinetic and kinaesthetic properties. PLP had multiple meanings to amputees, was considered a reminder of circumstances and could affect quality of life. Information provided about PLP was inadequate.

CONCLUSION

PLP can be a severe and annoying experience acting as a reminder of amputees' circumstances. Information provided about PLP is inadequate, with some amputees still perceiving PLP as mental and imaginary. Education about PLP and awareness and accessibility to non-pharmacological interventions needs to be improved.

[Amputation and prosthesis attachment of the lower extremities]

Approximately 61,000 amputations are performed in Germany per year. In most cases the lower limbs are affected. The reasons for amputations are arteriosclerosis, diabetes mellitus, severe infections, tumors and complex trauma to the extremities. A decision must be made concerning whether a salvage procedure or amputation is appropriate, specially after trauma. In cases where the need for amputation is clear, the site of amputation needs to be planned in advance with the aim of creating a stump which allows sufficient prosthetic attachment. Adjuvant pain therapy is mandatory, especially in order to avoid subsequent phantom pain. The type of prosthetic restoration is influenced by the grade of mobility and personal requirements of patients. Moreover, aftercare and adjusted rehabilitation are recommended.

Acupuncture for the treatment of phantom limb pain in lower limb amputees: study protocol for a randomized controlled feasibility trial

BACKGROUND

Phantom limb pain is a prevalent condition that is difficult to manage, with a lack of robust evidence to support the use of many adjunctive treatments. Acupuncture can be effective in the management of many painful conditions but little is known about its effectiveness in treating phantom limb pain. The aim of this study is to explore the feasibility of conducting a randomized controlled trial comparing acupuncture and routine care in a group of lower limb amputees with phantom limb pain.

METHODS/DESIGN

An unstratified, pragmatic, randomized, two-armed, controlled trial of parallel design comparing acupuncture and usual care control will be conducted. A total of 20 participants will be randomly assigned to receive either usual care or usual care plus acupuncture. Acupuncture will include eight 1 hour treatments delivered pragmatically over 4 weeks by practitioners trained in traditional Chinese medicine. As outcome measures, the Numerical Pain Rating Scale, short-form McGill Pain Questionnaire 2, EQ-5D-5 L, Hospital Anxiety and Depression Scale, 10-Item Perceived Stress Scale, Insomnia Severity Index, and Patient Global Impression of Change will be completed at baseline, weekly for the duration of the study and at 1 month after completion of the study. After completion of the trial, participants will provide feedback though semi-structured interviews. Feasibility will be determined through the ability to recruit to the study, success of the randomization process, completion of acupuncture intervention, acceptability of random allocation and completion of outcome measures. Acceptability of the acupuncture intervention will be determined through semi-structured interviews with participants. The appropriateness of outcome measures for a future trial will be addressed through completion rates of questionnaires and participant feedback.

DISCUSSION

Data generated on effect size will be used for future sample size calculations and will inform the development of an appropriate and feasible protocol for use in a definitive multicentre randomized controlled trial.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02126436.

Phantom eye syndrome: a review of the literature

The purpose of this literature review was to describe the main features of phantom eye syndrome in relation to their possible causes, symptoms, treatments, and influence of eye amputation on quality of life of anophthalmic patients. For this, a bibliographical research was performed in Pubmed database using the following terms: “eye amputation,” “eye trauma,” “phantom eye syndrome,” “phantom pain,” and “quality of life,” associated or not. Thirteen studies were selected, besides some relevant references contained in the selected manuscripts and other studies hallowed in the literature. Thus, 56 articles were included in this review. The phantom eye syndrome is defined as any sensation reported by the patient with anophthalmia, originated anophthalmic cavity. In phantom eye syndrome, at least one of these three symptoms has to be present: phantom vision, phantom pain, and phantom sensations. This syndrome has a direct influence on the quality of life of the patients, and psychological support is recommended before and after the amputation of the eyeball as well as aid in the treatment of the syndrome. Therefore, it is suggested that, for more effective treatment of phantom eye syndrome, drug therapy should be associated with psychological approach.

Pharmacology in peripheral arterial disease: what the interventional radiologist needs to know

Peripheral arterial disease (PAD) is a progressive disease with significant morbidity and mortality. Risk factor control, using diet and lifestyle modification, exercise, and pharmacological methods, improves symptoms and reduces associated cardiovascular events in these patients. Antiplatelet agents and anticoagulants may be used to reduce the incidence of acute events related to thrombosis. The armamentarium available for symptom relief and disease modification is discussed. Novel treatments such as therapeutic angiogenesis are in their evolutionary phase with promising preclinical data.

Recent insights into the mode of action of memantine and ketamine

The clinical benefits of the glutamate receptor antagonists memantine and ketamine have helped sustain optimism that glutamate receptors represent viable targets for development of therapeutic drugs. Both memantine and ketamine antagonize N-methyl-D-aspartate receptors (NMDARs), a glutamate receptor subfamily, by blocking the receptor-associated ion channel. Although many of the basic characteristics of NMDAR inhibition by memantine and ketamine appear similar, their effects on humans and to a lesser extent on rodents are strongly divergent. Some recent research suggests that preferential inhibition by memantine and ketamine of distinct NMDAR subpopulations may contribute to the drugs' differential clinical effects. Here we review studies that shed light on possible explanations for differences between the effects of memantine and ketamine.

"Doomed to go in company with miserable pain": surgical recognition and treatment of amputation-related pain on the Western Front during World War 1

The principal feature of injuries from World War 1 was musculoskeletal trauma and injury to peripheral nerves as a result of damage to the upper and lower limbs caused by gunshot wounds and fragments of artillery munitions. Amputation was used as a treatment in field hospitals to save lives; limb conservation was a secondary consideration. A century later, the principal feature of injuries to soldiers in today's wars in Iraq and Afghanistan is also musculoskeletal trauma and injury to the peripheral nerves caused by improvised explosive devices. Common to both types of injury is postamputation pain. We searched The Lancet's archives in this Series paper to show the efforts of surgeons in World War 1 to understand and treat postamputation pain in its own right both during and immediately after the war. Despite unprecedented patient numbers and levels of civilian medical expertise, little progress was made in providing relief from this type of pain, a grave concern to the surgeons treating these soldiers. Today postamputation pain is understood beyond a surgical context but remains a complex and poorly understood condition with few effective treatments.

Development of phantom limb pain after femoral nerve block

Historically, phantom limb pain (PLP) develops in 50–80% of amputees and may arise within days following an amputation for reasons presently not well understood. Our case involves a 29-year-old male with previous surgical amputation who develops PLP after the performance of a femoral nerve block. Although there have been documented cases of reactivation of PLP in amputees after neuraxial technique, there have been no reported events associated with femoral nerve blockade. We base our discussion on the theory that symptoms of phantom limb pain are of neuropathic origin and attempt to elaborate the link between regional anesthesia and PLP. Further investigation and understanding of PLP itself will hopefully uncover a relationship between peripheral nerve blocks targeting an affected limb and the subsequent development of this phenomenon, allowing physicians to take appropriate steps in prevention and treatment.

Drug repositioning: playing dirty to kill pain

The number of approved new molecular entity drugs has been decreasing as the pharmaceutical company investment in research and development is increasing. As we face this painful crisis, called an innovation gap, there is increasing awareness that development of new uses of existing drugs may be a powerful tool to help overcome this obstacle because it takes too long, costs too much and can be risky to release drugs developed de novo. Consequently, drug repositioning is emerging in different therapeutic areas, including the pain research area. Worldwide, pain is the main reason for seeking healthcare, and pain relief represents an unmet global clinical need. Therefore, development of analgesics with better efficacy, safety and cost effectiveness is of paramount importance. Despite the remarkable advancement in research on cellular and molecular mechanisms underlying pain pathophysiology over the past three decades, target-based therapeutic opportunities have not been pursued to the same extent. Phenotypic screening remains a more powerful tool for drug development than target-based screening so far. It sounds somewhat heretical, but some multi-action drugs, rather than very selective ones, have been developed intentionally. In the present review, we first critically discuss the utility of drug repositioning for analgesic drug development and then show examples of 'old' drugs that have been successfully repositioned or that are under investigation for their analgesic actions. We conclude that drug repositioning should be more strongly encouraged to help build a bridge between basic research and pain relief worldwide.

Challenging the catechism of therapeutics for chronic neuropathic pain: Targeting CaV2.2 interactions with CRMP2 peptides

Chronic neuropathic pain management is a worldwide concern. Pharmaceutical companies globally have historically targeted ion channels as the therapeutic catechism with many blockbuster successes. Remarkably, no new pain therapeutic has been approved by European or American regulatory agencies over the last decade. This article will provide an overview of an alternative approach to ion channel drug discovery: targeting regulators of ion channels, specifically focusing on voltage-gated calcium channels. We will highlight the discovery of an anti-nociceptive peptide derived from a novel calcium channel interacting partner - the collapsin response mediator protein 2 (CRMP2). In vivo administration of this peptide reduces pain behavior in a number of models of neuropathic pain without affecting sympathetic-associated cardiovascular activity, memory retrieval, sensorimotor function, or depression. A CRMP2-derived peptide analgesic, with restricted access to the CNS, represents a completely novel approach to the treatment of severe pain with an improved safety profile. As peptides now represent one of the fastest growing classes of new drugs, it is expected that peptide targeting of protein interactions within the calcium channel complex may be a paradigm shift in ion channel drug discovery.

Phantom limb pain: a systematic neuroanatomical-based review of pharmacologic treatment

OBJECTIVE

Review the current evidence-based pharmacotherapy for phantom limb pain (PLP) in the context of the current understanding of the pathophysiology of this condition.

DESIGN

We conducted a systematic review of original research papers specifically investigating the pharmacologic treatment of PLP. Literature was sourced from PubMed, Embase, Scopus, and the Cochrane Central Register of Controlled Trials (CENTRAL). Studies with animals, "neuropathic" but not "phantom limb" pain, or without pain scores and/or functional measures as primary outcomes were excluded. A level of evidence 1-4 was ascribed to individual treatments. These levels included meta-analysis or systematic reviews (level 1), one or more well-powered randomized, controlled trials (level 2), retrospective studies, open-label trials, pilot studies (level 3), and anecdotes, case reports, or clinical experience (level 4).

RESULTS

We found level 2 evidence for gabapentin, both oral (PO) and intravenous (IV) morphine, tramadol, intramuscular (IM) botulinum toxin, IV and epidural Ketamine, level 3 evidence for amitriptyline, dextromethorphan, topiramate, IV calcitonin, PO memantine, continuous perineural catheter analgesia with ropivacaine, and level 4 evidence for methadone, intrathecal (IT) buprenorphine, IT and epidural fentanyl, duloxetine, fluoxetine, mirtazapine, clonazepam, milnacipran, capsaicin, and pregabalin.

CONCLUSIONS

Currently, the best evidence (level 2) exists for the use of IV ketamine and IV morphine for the short-term perioperative treatment of PLP and PO morphine for an intermediate to long-term treatment effect (8 weeks to 1 year). Level 2 evidence is mixed for the efficacy of perioperative epidural anesthesia with morphine and bupivacaine for short to long-term pain relief (perioperatively up to 1 year) as well as for the use of gabapentin for pain relief of intermediate duration (6 weeks).

Clinical pharmacology of analgesics assessed with human experimental pain models: bridging basic and clinical research

The medical impact of pain is such that much effort is being applied to develop novel analgesic drugs directed towards new targets and to investigate the analgesic efficacy of known drugs. Ongoing research requires cost-saving tools to translate basic science knowledge into clinically effective analgesic compounds. In this review we have re-examined the prediction of clinical analgesia by human experimental pain models as a basis for model selection in phase I studies. The overall prediction of analgesic efficacy or failure of a drug correlated well between experimental and clinical settings. However, correct model selection requires more detailed information about which model predicts a particular clinical pain condition. We hypothesized that if an analgesic drug was effective in an experimental pain model and also a specific clinical pain condition, then that model might be predictive for that particular condition and should be selected for development as an analgesic for that condition. The validity of the prediction increases with an increase in the numbers of analgesic drug classes for which this agreement was shown. From available evidence, only five clinical pain conditions were correctly predicted by seven different pain models for at least three different drugs. Most of these models combine a sensitization method. The analysis also identified several models with low impact with respect to their clinical translation. Thus, the presently identified agreements and non-agreements between analgesic effects on experimental and on clinical pain may serve as a solid basis to identify complex sets of human pain models that bridge basic science with clinical pain research.

Evidence of prescription of antidepressants for non-psychiatric conditions in primary care: an analysis of guidelines and systematic reviews

BACKGROUND

Antidepressants (ADs) are commonly prescribed in primary care and are mostly indicated for depression. According to the literature, they are now more frequently prescribed for health conditions other than psychiatric ones. Due to their many indications in a wide range of medical fields, assessing the appropriateness of AD prescription seems to be a challenge for GPs. The aim of this study was to review evidence from guidelines for antidepressant prescription for non-psychiatric conditions in Primary Care (PC) settings.

METHODS

Data were retrieved from French, English and US guideline databases. Guidelines or reviews were eligible if keywords regarding 44 non-psychiatric conditions related to GPs' prescription of ADs were encountered. After excluding psychiatric and non-primary care conditions, the guidelines were checked for keywords related to AD use. The latest updated version of the guidelines was kept. Recent data was searched in the Cochrane Database of Systematic Reviews and in PubMed for updated reviews and randomized control trials (RCTs).

RESULTS

Seventy-eight documents were retrieved and were used to assess the level of evidence of a potential benefit to prescribing an AD. For 15 conditions, there was a consensus that prescribing an AD was beneficial. For 5 others, ADs were seen as potentially beneficial. No proof of benefit was found for 15 conditions and proof of no benefit was found for the last 9. There were higher levels of evidence for pain conditions, (neuropathic pain, diabetic painful neuropathy, central neuropathic pain, migraine, tension-type headaches, and fibromyalgia) incontinence and irritable bowel syndrome. There were difficulties in summarizing the data, due to a lack of information on the level of evidence, and due to variations in efficacy between and among the various classes of ADs.

CONCLUSIONS

Prescription of ADs was found to be beneficial for many non-psychiatric health conditions regularly encountered in PC settings. On the whole, the guidelines were heterogeneous, seemingly due to a lack of trials assessing the role of ADs in treatment strategies.

[Phantom limb pain. Psychological treatment strategies]

Similar to other pain syndromes phantom limb pain is characterized by learning and memory processes that maintain the pain and increase maladaptive plastic changes of the brain: therefore, psychological interventions that change maladaptive memory processes are useful. In addition to traditional psychological interventions, such as pain management training and biofeedback, more recent developments that involve sensory discrimination training, mirror treatment, graded motor imagery, prosthesis training and training in virtual reality are interesting. These interventions not only reduce phantom limb pain but also reverse the associated maladaptive brain changes.

Effects of low-dose IV ketamine on peripheral and central pain from major limb injuries sustained in combat

OBJECTIVE

Examine response patterns to low-dose intravenous (IV) ketamine continuous infusions on multiple pain outcomes, and demonstrate effectiveness, safety, and tolerability of ketamine administration on general wards.

DESIGN

Retrospective case series of consecutive patients given low-dose IV ketamine continuous infusions.

SETTING

Walter Reed Army Medical Center, Washington, DC.

PATIENTS

Nineteen eligible inpatients with neuropathic pain from major limb injuries sustained in combat with inadequate pain control from multimodal analgesia.

INTERVENTIONS

A 3-day IV infusion of ketamine at doses ≤ 120 μg/kg/h.

OUTCOME MEASURES

Daily present (PPI), average (API), and worst (WPI) pain intensity (0-10), global pain relief (GPR) (1 "no relief" to 5 "complete relief"), daily assessments of adverse events, and daily opioid requirements measured during therapy.

RESULTS

A significant reduction in PPI (P < 0.001) and improvement in GPR (P = 0.031) was noted over time. Higher baseline WPI (≥ 7; N = 4) was associated with a significant decrease in WPI (P = 0.0388), but lower baseline WPI (N = 5) was not. Significant mean percent decreases in PPI with higher baseline PPI (N = 8; P = 0.0078) and WPI with no phantom limb pain (PLP) (N = 10; P = 0.0436) were observed. Mean percent increase in overall GPR was better for those reporting GPR scores ≤ 3 (N = 13) in the first 24 hours of therapy (P = 0.0153). While not significant, mean opioid requirement (IV morphine equivalents) decreased from 129.9 mgs ± 137.3 on day 1 to 112.14 ± 86.3 24 hours after therapy.

CONCLUSIONS

Low-dose ketamine infusions for complex combat injury pain were safe and effective, and demonstrated response patterns over time and by baseline pain score stratification and presence or absence of PLP.

Evaluation of the efficacy of memantine in the treatment of fibromyalgia: study protocol for a doubled-blind randomized controlled trial with six-month follow-up

Background

Fibromyalgia is a prevalent chronic rheumatic disease of great clinical importance. Recent studies have found raised levels of glutamate in the insula, hippocampus and posterior cingulate cortex regions of the brains of fibromyalgia (FM) patients. This finding has led researchers to speculate about the usefulness of glutamate-blocking drugs such as memantine in the treatment of fibromyalgia. The hypothesis of this study is that the administration of memantine will reduce the glutamate levels, and futhermore, will decrease the perceived pain. The aim of this study is to evaluate the efficacy of memantine in the treatment of pain (pain perception). A secondary objective is to evaluate the efficacy of memantine in the treatment of other clinical symptoms of FM, and to evaluate the efficacy of memantine in reducing brain levels of glutamate, and its effects on the central nervous system as a whole.

Method/Design

A double-blind parallel randomized controlled trial. Participants, Seventy patients diagnosed with FM will be recruited from primary health care centers in Zaragoza, Spain. Intervention. The subjects will be randomized in two groups: A) A treatment group (n = 35), which will receive 20 mg of memantine daily; B) A control group (n = 35), to which will be administered a placebo. There will be a six-month follow-up period (including a titration period of one month). Outcomes. The main efficacy variable of this study is pain (pain perception). The secondary efficacy variables are clinical symptoms (pain threshold, cognitive function, health status, anxiety, depression, clinical impression and quality of life) and glutamate levels in different regions of the brain, which will be assessed by magnetic resonance spectroscopy. Randomization and blinding. Randomization has been computer-generated, and the random allocation sequence will be implemented by telephone. Subjects of the study and the research assistants will be blinded to group assignment.

Discussion

There is a need for the development of innovative and more effective treatments for fibromyalgia. This clinical trial will determine whether memantine can be an effective pharmacological treatment for fibromyalgia patients.

Trial registration

Current Controlled Trials http://ISRCTN45127327 EUDRACT 2011-006244-73