Pregabalin Vs. Opioids for the Treatment of Neuropathic Cancer Pain: A Prospective, Head-to-Head, Randomized, Open-Label Study

Opioid analgesics for nociceptive cancer pain: A comprehensive review

Pain is one of the most burdensome symptoms in people with cancer, and opioid analgesics are considered the mainstay of cancer pain management. For this review, the authors evaluated the efficacy and toxicities of opioid analgesics compared with placebo, other opioids, nonopioid analgesics, and nonpharmacologic treatments for background cancer pain (continuous and relatively constant pain present at rest), and breakthrough cancer pain (transient exacerbation of pain despite stable and adequately controlled background pain). They found a paucity of placebo-controlled trials for background cancer pain, although tapentadol or codeine may be more efficacious than placebo (moderate-certainty to low-certainty evidence). Nonsteroidal anti-inflammatory drugs including aspirin, piroxicam, diclofenac, ketorolac, and the antidepressant medicine imipramine, may be at least as efficacious as opioids for moderate-to-severe background cancer pain. For breakthrough cancer pain, oral transmucosal, buccal, sublingual, or intranasal fentanyl preparations were identified as more efficacious than placebo but were more commonly associated with toxicities, including constipation and nausea. Despite being recommended worldwide for the treatment of cancer pain, morphine was generally not superior to other opioids, nor did it have a more favorable toxicity profile. The interpretation of study results, however, was complicated by the heterogeneity in the study populations evaluated. Given the limited quality and quantity of research, there is a need to reappraise the clinical utility of opioids in people with cancer pain, particularly those who are not at the end of life, and to further explore the effects of opioids on immune system function and quality of life in these individuals.

The impact of a restricted pregabalin prescription policy on drug utilization: An observational multicenter study

Background

The Saudi Food and Drug Authority (SFDA) classified pregabalin as a controlled substance in 2018; however, whether this policy change has affected pregabalin use is unclear. This study examined the trends in pregabalin prescriptions before and after the SFDA restriction. In addition, the co-prescription of controlled analgesics and the use of pregabalin for approved indications were also evaluated.

Method

A cross-sectional study was conducted on outpatient pregabalin prescriptions from three healthcare centers in Saudi Arabia. Interrupted time series analysis was used to assess changes over time in pregabalin prescriptions and the number of patients receiving pregabalin. June 2016 to June 2017 was identified as the pre-restriction period, and July 2018 to July 2019 as the post-restriction period.

Results

In this study, 77,760 pregabalin prescriptions were identified. There were 9,076 patients on pregabalin in the pre-restriction period with 16,875 prescriptions, compared with 7,123 patients and 19,484 prescriptions post-restriction. The total number of pregabalin users decreased by 21.5% post-restriction, and prescriptions increased by 15.5%. There was no significant change in the monthly trends in pregabalin prescriptions before and after the restriction. However, the of tramadol and acetaminophen/codeine prescriptions in patients who were using pregabalin increased in the post-restriction period by 21% and 16.1%, respectively.

Conclusion

Pregabalin use was reduced after the SFDA-enforced prescription restriction was implemented. This was accompanied by increased narcotics use in the post-implementation phase.

Use of Opioids for Adults With Pain From Cancer or Cancer Treatment: ASCO Guideline

PURPOSE

To provide guidance on the use of opioids to manage pain from cancer or cancer treatment in adults.

METHODS

A systematic review of the literature identified systematic reviews and randomized controlled trials of the efficacy and safety of opioid analgesics in people with cancer, approaches to opioid initiation and titration, and the prevention and management of opioid adverse events. PubMed and the Cochrane Library were searched from January 1, 2010, to February 17, 2022. American Society of Clinical Oncology convened an Expert Panel to review the evidence and formulate recommendations.

RESULTS

The evidence base consisted of 31 systematic reviews and 16 randomized controlled trials. Opioids have primarily been evaluated in patients with moderate-to-severe cancer pain, and they effectively reduce pain in this population, with well-characterized adverse effects. Evidence was limited for several of the questions of interest, and the Expert Panel relied on consensus for these recommendations or noted that no recommendation could be made at this time.

RECOMMENDATIONS

Opioids should be offered to patients with moderate-to-severe pain related to cancer or active cancer treatment unless contraindicated. Opioids should be initiated PRN (as needed) at the lowest possible dose to achieve acceptable analgesia and patient goals, with early assessment and frequent titration. For patients with a substance use disorder, clinicians should collaborate with a palliative care, pain, and/or substance use disorder specialist to determine the optimal approach to pain management. Opioid adverse effects should be monitored, and strategies are provided for prevention and management.Additional information is available at www.asco.org/supportive-care-guidelines.

Treatment of Neuropathic Pain Directly Due to Cancer: An Update

Simple Summary

This review discusses treatment approaches for providing pain relief to oncological patients affected by pain caused by nerve damage due to the tumor, also known as neuropathic cancer pain. Although being encountered often and causing a relevant burden to these patients, neuropathic cancer pain remains still difficult to diagnose and treat. Strong evidence about the best drugs to be used remain limited, as do therapeutic choices.

Abstract

Neuropathic pain can be defined as pain related to abnormal somatosensory processing in either the peripheral or central nervous system. In this review article, with neuropathic cancer pain (NCP), we refer to pain due to nervous tissue lesions caused by the tumor or its metastases. Nervous tissue damage is the cause of cancer pain in approximately 40% of those experiencing cancer pain. Recognizing a neuropathic pathophysiology in these cases may be difficult and requires specific criteria that are not homogenously applied in clinical practice. The management of this type of pain can be challenging, requiring the use of specific non-opioid adjuvant drugs. The majority of the criteria for NCP diagnosis and management have been based mainly on results from the noncancer population, risking the failure of addressing the specific needs of this population of patients. In this review, we summarize current management options available for NCP and provide some insights on new promising treatments.

Revision of Pharmacological Treatment Recommendations for Cancer Pain: Clinical Guidelines from the Japanese Society of Palliative Medicine

Background: Pain is one of the most common symptoms in cancer patients. The Japanese Society for Palliative Medicine (JSPM) first published its clinical guidelines for the management of cancer pain in 2010. Since then, more research on cancer pain management has been reported, and new drugs have become available in Japan. Thus, the JSPM has now revised the clinical guidelines using a validated methodology. Methods: This guideline was developed through a systematic review, discussion, and the Delphi method, following a formal guideline development process. Results: Thirty-five recommendations were created: 19 for the pharmacological management of cancer pain, 6 for the management of opioid-induced adverse effects, and 10 for pharmacological treatment procedures. Due to the lack of evidence that directly addressed our clinical questions, most of the recommendations had to be based on consensus among committee members and other guidelines. Discussion: It is critical to continue to build high-quality evidence in cancer pain management, and revise these guidelines accordingly.

Interventional and Non-interventional Medical Rehabilitation Approaches to Axial Spine Pain in Vertebral Metastatic Disease

As targeted therapies help patients with advanced cancer live longer, interventions for management of axial spine pain will become more common. Unfortunately, the indications for and safety of these procedures have been relatively unexplored compared with non-cancer adults. This review focuses on the following aspects of axial spine pain management in patients with vertebral metastatic disease: (1) pathophysiology and symptoms of cancer- and non-cancer-related spine pain; (2) safety and efficacy of non-interventional rehabilitation approaches to treat this pain; (3) considerations for interventional pain approaches to acute and chronic pain in patients with vertebral metastatic disease. This review also summarizes gaps in the literature and describes specific cases in which the described interventions have been applied.

Opioid Analgesia and Opioid-Induced Adverse Effects: A Review

Opioids are widely used as therapeutic agents against moderate to severe acute and chronic pain. Still, these classes of analgesic drugs have many potential limitations as they induce analgesic tolerance, addiction and numerous behavioural adverse effects that often result in patient non-compliance. As opium and opioids have been traditionally used as painkillers, the exact mechanisms of their adverse reactions over repeated use are multifactorial and not fully understood. Older adults suffer from cancer and non-cancer chronic pain more than younger adults, due to the physiological changes related to ageing and their reduced metabolic capabilities and thus show an increased number of adverse reactions to opioid drugs. All clinically used opioids are μ-opioid receptor agonists, and the major adverse effects are directly or potentially connected to this receptor. Multifunctional opioid ligands or peripherally restricted opioids may elicit fewer adverse effects, as shown in preclinical studies, but these results need reproducibility from further extensive clinical trials. The current review aims to overview various mechanisms involved in the adverse effects induced by opioids, to provide a better understanding of the underlying pathophysiology and, ultimately, to help develop an effective therapeutic strategy to better manage pain.

The Greek Neuropathic Pain Registry: The structure and objectives of the sole NPR in Greece

OBJECTIVES

Neuropathic pain (NP) is a complex condition that impairs the patients' quality of life. Registries are useful tools, increasingly used as they provide high-quality data. This article aims to describe the Greek Neuropathic Pain Registry (Gr.NP.R.) design, the patients' baseline data, and real-world treatment outcomes.

METHODS

The Gr.NP.R. collects electronically, stores, and shares real-world clinical data from Pain and Palliative Care centers in Greece. It is a web-based application, which ensures security, simplicity, and transparency. VAS, DN4, and Pain Detect were used for pain and NP assessment.

RESULTS

From 2016 to 2020, 5980 patients with chronic pain, of cancer or non-cancer origin, were examined and 2334 fulfilled the NP inclusion criteria (VAS > 5, DN4 > 4, and Pain Detect ≥ 19). At the first visit, the mean age was 64.8 years, 65.5% were female patients, and 97.9% were Greek. The mean (SD) time from pain initiation to visiting the pain clinics was 1.5 (3.8) years. Most patients were undertreated. Following the patients' registration, the national guidelines were implemented. The majority of the prescribed medications were gabapentinoids (70.2%), especially pregabalin (62.6%), and opioids (tramadol, 55.3%). At visits 1 and 6, mean VAS was 7.1 and 5, and mean DN4 score was 5.6 and 3.5, respectively.

CONCLUSIONS

The Gr.NP.R. provides information on the demographics, clinical progress, treatment history, treatment responses, and the drugs of choice for patients with cancer and non-cancer NP. The collected data may help physicians plan the management of their patients.

The current clinical use of adjuvant analgesics for refractory cancer pain in Japan: a nationwide cross-sectional survey

BACKGROUND

Although adjuvant analgesics are used to treat opioid-refractory cancer pain, there is insufficient evidence to support this practice and limited data to guide the choice depending on cancer pain pathophysiology, dose titration and starting dose. This survey aimed to clarify the current use of adjuvant analgesics for treating opioid-refractory cancer pain.

METHODS

In this cross-sectional study, we sent an online survey questionnaire to 208 certified palliative care specialists. Primary outcomes were (i) effective pathophysiological mechanism of cancer pain and (ii) initiating doses and time period to the first response to each adjuvant analgesic therapy.

RESULTS

In total, 87 (42%) palliative care specialists responded. Of all patients with cancer pain, 40% of patients (median) with refractory cancer pain were prescribed adjuvant analgesics. Additionally, 94.3, 93.1 and 86.2% of palliative care specialists found dexamethasone/betamethasone effective for neuropathic pain caused by tumor-related spinal cord compression, pregabalin effective for malignant painful radiculopathy and dexamethasone/betamethasone effective for brain tumor or leptomeningeal metastases-related headache, respectively. The median starting dose of pregabalin, dexamethasone/betamethasone, lidocaine and ketamine were 75, 4, 200, and 50 mg/day, respectively, and the median time to the first response of those medications were 5, 3, 2 and 3 days, respectively.

CONCLUSIONS

Many palliative care specialists select adjuvant analgesics depending on the pathophysiological mechanism of cancer pain in each case. They used such adjuvant analgesics in low doses for cancer pain with short first-response periods.

Non-opioid Analgesics and Emerging Therapies

Pain is a common and debilitating symptom of cancer. Cancer-related pain can occur at any point along the continuum from diagnosis to treatment to survivorship¹. A systematic review published in 2016 estimated the prevalence of cancer pain to be 55% in those undergoing antineoplastic treatment, 66.4% in advanced cancer, and 39.3% in the post-treatment population. Thirty-eight percent of cancer patients in this pooled analysis experienced moderate to severe pain².

Response to pregabalin and progesterone differs in male and female rat models of neuropathic and cancer pain

Background: Cancer pain involves nervous system damage and pathological neurogenesis. Neuropathic pain arises from damage to the nervous system and is driven by ectopic signaling. Both progesterone and pregabalin are neuroprotective in animal models, and there is evidence that both drugs bind to and inhibit voltage-gated calcium channels. Aims: This study was designed to characterize the effects of progesterone and pregabalin in preclinical models of cancer and neuropathic pain in both sexes. Methods: We measured peripheral sensory signaling by intracellular in vivo electrophysiology and behavioral indicators of pain in rat models of cancer-induced bone pain and neuropathic pain. Results: Female but not male models of cancer pain showed a behavioral response to treatment and pregabalin reduced excitability in C and A high-threshold but not low-threshold sensory neurons of both sexes. Male models of neuropathic pain treated with pregabalin demonstrated higher signaling thresholds only in A high-threshold neurons, and behavioral data indicated a clear recovery to baseline mechanical withdrawal thresholds in all treatment groups. Female rat treatment groups did not show excitability changes in sensory neurons, but all demonstrated higher mechanical withdrawal thresholds than vehicle-treated females, although not to baseline levels. Athymic female rat models of neuropathic pain showed no behavioral or electrophysiological responses to treatment. Conclusions: Both pregabalin and progesterone showed evidence of efficacy in male models of neuropathic pain. These results add to the evidence demonstrating differential effects of treatments for pain in male and female animals and widely differing responses in models of cancer and neuropathic pain.

Adult Cancer Pain, Version 3.2019, NCCN Clinical Practice Guidelines in Oncology

In recent years, the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Adult Cancer Pain have undergone substantial revisions focusing on the appropriate and safe prescription of opioid analgesics, optimization of nonopioid analgesics and adjuvant medications, and integration of nonpharmacologic methods of cancer pain management. This selection highlights some of these changes, covering topics on management of adult cancer pain including pharmacologic interventions, nonpharmacologic interventions, and treatment of specific cancer pain syndromes. The complete version of the NCCN Guidelines for Adult Cancer Pain addresses additional aspects of this topic, including pathophysiologic classification of cancer pain syndromes, comprehensive pain assessment, management of pain crisis, ongoing care for cancer pain, pain in cancer survivors, and specialty consultations.

Reviewing without a Clinical Background Is Detrimental for Cancer Pain Management

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

A critical appraisal of gabapentinoids for pain in cancer patients

PURPOSE OF REVIEW

Gabapentinoids are frequently used in the management of cancer pain. In recent Cochrane systematic reviews, although there was an abundance of evidence relating to non-cancer pain, only a few studies related to cancer pain. This review summarizes recent randomised controlled trials (RCTs) evaluating the use of gabapentinoids for tumour-related (as monotherapy or part of combination therapy) and treatment-related pain.

RECENT FINDINGS

For tumour-related pain, ten out of thirteen studies showed statistically significant benefits in favour of gabapentinoids. When used, as part of monotherapy or combination therapy, benefits were observed in five out of six studies evaluating gabapentin, and in six out of eight studies evaluating pregabalin. For treatment-related pain, none of the four studies (two gabapentin, two pregabalin) showed statistically significant benefits in favour of gabapentinoids. Unfortunately, many of the studies included were limited by small sample size, lack of blinding, and inadequate follow-up.

SUMMARY

More and better quality studies are required, although it may be challenging to accomplish in this patient population. Gabapentinoids may offer benefits to cancer patients with pain, but careful titration and monitoring of adverse effects is necessary.

Gabapentin versus Transdermal Fentanyl Matrix for the Alleviation of Chronic Neuropathic Pain of Radicular Origin: A Randomized Blind Multicentered Parallel-Group Noninferiority Trial

A number of studies have been published proposing various approaches to the treatment of neuropathic pain; however, to our knowledge, no attempts have been made to compare gabapentin and fentanyl in patients with lumbar radiculopathy. We evaluated the relative efficacy and safety of fentanyl matrix and gabapentin for the treatment of chronic neuropathic pain of radicular origin. The study was designed as a randomized blind multicentered parallel-group noninferiority trial. A total of 108 patients with moderate-to-severe pain (≥4 intensity on an 11-point numeric rating scale) were randomly prescribed either fentanyl matrix or gabapentin over a period of 56 days. In the primary analysis, the noninferiority of fentanyl matrix treatment was evaluated in relation to the efficacy of gabapentin based on the pain intensity difference (PID) at 56 days after the first dose of the drugs. Secondary endpoints included pain relief, improvement in functional status (the Korean-Oswestry Disability Index (K-ODI)), improvement in depressive symptoms (Korean-Beck Depression Index (K-BDI)) between the 28th and 56th day, and adverse events (AEs). Analysis of the primary efficacy endpoint established the noninferiority of fentanyl matrix compared with gabapentin, with no statistically significant difference observed in the PID after 56 days for the two treatment groups. Similarly, analysis of pain relief revealed no significant differences between the groups on days 28 and 56. There was no difference in the K-ODI and K-BDI between the groups during the study period. The overall incidence of at least one AE was similar for fentanyl matrix (67.3%) and gabapentin (69.6%). The most commonly reported AEs for patients treated with fentanyl matrix and gabapentin included dizziness (30.8% vs. 44.6%, respectively), somnolence (26.9% vs. 35.7%), and constipation (15.4% vs. 17.9%). This study demonstrated that the analgesic effect of fentanyl matrix is noninferior in comparison with gabapentin and supports the use of fentanyl matrix as an effective and safe treatment for moderate-to-severe chronic neuropathic pain. This trial is registered with NCT01127100.

A Retrospective Analysis of Pain Burden in Hospitalized Young Adult Cancer Patients Compared with Their Older Adult Counterpart

CONTEXT

Research shows an increased symptom burden in young adult (YA) cancer patients compared with their older adult counterpart.

OBJECTIVES

The purpose of this study was to identify differences in clinical characteristics and related outcomes between YA and older adult cancer patients admitted for cancer-related pain.

MATERIALS AND METHODS

We retrospectively identified 190 hospitalized patients in a single academic center with admissions for cancer-related pain. Patients were grouped into either "young adult" (18-39) or "older adult" (>40) cohorts. We compared differences in patient characteristics and pain regimens.

RESULTS

Median oral morphine equivalent per 24 hours was higher in the YA group (194 mg vs. 70 mg, p = 0.010). Younger patients received patient-controlled analgesia (PCA) more frequently (p = 0.023). The number of palliative care consults and adjuvants prescribed did not differ between groups (p > 0.05), although YAs more frequently had an inpatient pain anesthesia consult (p = 0.047).

CONCLUSION

Findings show increased opioid requirements and PCA use in YAs being treated for malignancy compared with their older adult counterpart.

Cancer-Related Neuropathic Pain: Review and Selective Topics

Neuropathic pain is the result of neuroplastic and neuroinflammatory changes from trauma or diseases that damage the somatosensory system. Cancer-related neuropathic pain is caused by treatment, cancer, or paraneoplastic reactions to cancer. Approximately 30% of patients with cancer have neuropathic pain, mostly mixed nociceptive and neuropathic pain. History, physical examination, quantitative sensory testing, skin punch biopsies, and functional MRIs help to divide pain into phenotypes that may facilitate analgesic choices. Guidelines for treating cancer-related neuropathic pain are not consistent and are highly dependent on trials in patients without cancer. Combinations of analgesics are promising, whereas evidence for cannabinoids is meager.

Methadone for cancer pain

BACKGROUND

This is an updated review originally published in 2004 and first updated in 2007. This version includes substantial changes to bring it in line with current methodological requirements. Methadone is a synthetic opioid that presents some challenges in dose titration and is recognised to cause potentially fatal arrhythmias in some patients. It does have a place in therapy for people who cannot tolerate other opioids but should be initiated only by experienced practitioners. This review is one of a suite of reviews on opioids for cancer pain.

OBJECTIVES

To determine the effectiveness and tolerability of methadone as an analgesic in adults and children with cancer pain.

SEARCH METHODS

For this update we searched CENTRAL, MEDLINE, Embase, CINAHL, and clinicaltrials.gov, to May 2016, without language restriction. We also checked reference lists in relevant articles.

SELECTION CRITERIA

We sought randomised controlled trials comparing methadone (any formulation and by any route) with active or placebo comparators in people with cancer pain.

DATA COLLECTION AND ANALYSIS

All authors agreed on studies for inclusion. We retrieved full texts whenever there was any uncertainty about eligibility. One review author extracted data, which were checked by another review author. There were insufficient comparable data for meta-analysis. We extracted information on the effect of methadone on pain intensity or pain relief, the number or proportion of participants with 'no worse than mild pain'. We looked for data on withdrawal and adverse events. We looked specifically for information about adverse events relating to appetite, thirst, and somnolence. We assessed the evidence using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

We revisited decisions made in the earlier version of this review and excluded five studies that were previously included. We identified one new study for this update. This review includes six studies with 388 participants. We did not identify any studies in children.The included studies differed so much in their methods and comparisons that no synthesis of results was feasible. Only one study (103 participants) specifically reported the number of participants with a given level of pain relief, in this case a reduction of at least 20% - similar in both the methadone and morphine groups. Using an outcome of 'no worse than mild pain', methadone was similar to morphine in effectiveness, and most participants who could tolerate methadone achieved 'no worse than mild pain'. Adverse event withdrawals with methadone were uncommon (12/202) and similar in other groups. Deaths were uncommon except in one study where the majority of participants died, irrespective of treatment group. For specific adverse events, somnolence was more common with methadone than with morphine, while dry mouth was more common with morphine than with methadone. None of the studies reported effects on appetite.We judged the quality of evidence to be low, downgraded due to risk of bias and sparse data. For specific adverse events, we considered the quality of evidence to be very low, downgraded due to risk of bias, sparse data, and indirectness, as surrogates for appetite, thirst and somnolence were used.There were no data on the use of methadone in children.

AUTHORS' CONCLUSIONS

Based on low-quality evidence, methadone is a drug that has similar analgesic benefits to morphine and has a role in the management of cancer pain in adults. Other opioids such as morphine and fentanyl are easier to manage but may be more expensive than methadone in many economies.

Fentanyl for neuropathic pain in adults

BACKGROUND

Opioid drugs, including fentanyl, are commonly used to treat neuropathic pain, and are considered effective by some professionals. Most reviews have examined all opioids together. This review sought evidence specifically for fentanyl, at any dose, and by any route of administration. Other opioids are considered in separate reviews.

OBJECTIVES

To assess the analgesic efficacy of fentanyl for chronic neuropathic pain in adults, and the adverse events associated with its use in clinical trials.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and Embase from inception to June 2016, together with the reference lists of retrieved articles, and two online study registries.

SELECTION CRITERIA

We included randomised, double-blind studies of two weeks' duration or longer, comparing fentanyl (in any dose, administered by any route, and in any formulation) with placebo or another active treatment in chronic neuropathic pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched for studies, extracted efficacy and adverse event data, and examined issues of study quality and potential bias. We did not carry out any pooled analyses. We assessed the quality of the evidence using GRADE.

MAIN RESULTS

Only one study met our inclusion criteria. Participants were men and women (mean age 67 years), with postherpetic neuralgia, complex regional pain syndrome, or chronic postoperative pain. They were experiencing inadequate relief from non-opioid analgesics, and had not previously taken opioids for their neuropathic pain. The study used an enriched enrolment randomised withdrawal design. It was adequately blinded, but we judged it at unclear risk of bias for other criteria.Transdermal fentanyl (one-day fentanyl patch) was titrated over 10 to 29 days to establish the maximum tolerated and effective dose (12.5 to 50 µg/h). Participants who achieved a prespecified good level of pain relief with a stable dose of fentanyl, without excessive use of rescue medication or intolerable adverse events ('responders'), were randomised to continue with fentanyl or switch to placebo for 12 weeks, under double-blind conditions. Our prespecified primary outcomes were not appropriate for this study design, but the measures reported do give an indication of the efficacy of fentanyl in this condition.In the titration phase, 1 in 3 participants withdrew because of adverse events or inadequate pain relief, and almost 90% experienced adverse events. Of 258 participants who underwent open-label titration, 163 were 'responders' and entered the randomised withdrawal phase. The number of participants completing the study (and therefore continuing on treatment) without an increase of pain by more than 15/100 was 47/84 (56%) with fentanyl and 28/79 (35%) with placebo. Because only 63% responded sufficiently to enter the randomised withdrawal phase, this implies that only a maximum of 35% of participants entering the study would have had useful pain relief and tolerability with transdermal fentanyl, compared with 22% with placebo. Almost 60% of participants taking fentanyl were 'satisfied' and 'very satisfied' with their treatment at the end of the study, compared with about 40% with placebo. This outcome approximates to our primary outcome of moderate benefit using the Patient Global Impression of Change scale, but the group was enriched for responders and the method of analysis was not clear. The most common adverse events were constipation, nausea, somnolence, and dizziness.There was no information about other types of neuropathic pain, other routes of administration, or comparisons with other treatments.We downgraded the quality of the evidence to very low because there was only one study, with few participants and events, and there was no information about how data from people who withdrew were analysed.

AUTHORS' CONCLUSIONS

There is insufficient evidence to support or refute the suggestion that fentanyl works in any neuropathic pain condition.

Analgesic effectiveness and tolerability of oral oxycodone/naloxone and pregabalin in patients with lung cancer and neuropathic pain: an observational analysis

INTRODUCTION

Cancer-related pain has a severe negative impact on quality of life. Combination analgesic therapy with oxycodone and pregabalin is effective for treating neuropathic cancer pain. We investigated the efficacy and tolerability of a dose-escalation combination therapy with prolonged-release oxycodone/naloxone (OXN-PR) and pregabalin in patients with non-small-cell lung cancer and severe neuropathic pain.

METHODS

This was a 4-week, open-label, observational study. Patients were treated with OXN-PR and pregabalin. Average pain intensity ([API] measured on a 0-10 numerical rating scale) and neuropathic pain (Douleur Neuropathique 4) were assessed at study entry and at follow-up visits. The primary endpoint was response to treatment, defined as a reduction of API at T28 ≥30% from baseline. Secondary endpoints included other efficacy measures, as well as patient satisfaction and quality of life (Brief Pain Inventory Short Form), Hospital Anxiety and Depression Scale, and Symptom Distress Scale; bowel function was also assessed.

RESULTS

A total of 56 patients were enrolled. API at baseline was 8.0±0.9, and decreased after 4 weeks by 48% (4.2±1.9; P<0.0001 vs baseline); 46 (82.1%) patients responded to treatment. Significant improvements were also reported in number/severity of breakthrough cancer pain episodes (P=0.001), Brief Pain Inventory Short Form (P=0.0002), Symptom Distress Scale (P<0.0001), Hospital Anxiety and Depression Scale depression (P=0.0006) and anxiety (P<0.0001) subscales, and bowel function (P=0.0003). At study end, 37 (66.0%) patients were satisfied/very satisfied with the new analgesic treatment. Combination therapy had a good safety profile.

CONCLUSION

OXN-PR and pregabalin were safe and highly effective in a real-world setting of severe neuropathic cancer pain, with a high rate of satisfaction, without interference on bowel function.

A retrospective study to identify risk factors for somnolence and dizziness in patients treated with pregabalin

Background

Pregabalin is a therapeutic drug for neuropathic pain that is associated with somnolence and dizziness. These adverse events are often experienced shortly after initiating pregabalin, and may lead to treatment discontinuation. The purpose of this study was to explore factors that influence the incidence of somnolence and dizziness induced by pregabalin, and to identify patients at higher risk of adverse events.

Methods

A retrospective analysis was conducted of patient characteristics (age, gender, renal function, initial daily dose of pregabalin, co-administration of strong opioids and hypnotics) and the incidence of somnolence and dizziness during the first week of pregabalin treatment. An electronic chart was used to collect data from 204 inpatients prescribed pregabalin at Nagoya University Hospital from June 2011 to November 2012.

Results

Among 36 patients who regularly received strong opioids, 18 (50.0 %) reported somnolence or dizziness during the first week of pregabalin treatment. The remaining 168 patients did not regularly receive strong opioids, and 25 (14.9 %) had an adverse event. In multivariate analysis, age (≧65 years, adjusted odds ratio: 2.507, 95 % CI: 1.164-5.397, p = 0.019) and regular co-administration of strong opioids (adjusted odds ratio: 5.507, 95 % CI: 2.460-12.328, p < 0.001) correlated with somnolence or dizziness.

Conclusions

These data suggest that age (≧65 years) and co-administration of strong opioids are risk factors for somnolence or dizziness during pregabalin treatment for neuropathic pain. More careful dose titration is recommended for elderly patients and those receiving concomitant strong opioids.

Novel use of perineural pregabalin infusion for analgesia in a rat neuropathic pain model

BACKGROUND

The anticonvulsant drugs pregabalin and gabapentin are often used systemically to treat some forms of chronic neuropathic pain. However, many patients report side effects serious enough to cause discontinuation of the drug. Here we present evidence that pregabalin may block neuropathic pain when applied to the site of nerve injury in a rat neuropathic pain model.

METHODS

Forty male Sprague Dawley rats were randomized into 4 groups: sciatic nerve crush injury with perineural pregabalin treatment (treatment), crush injury with perineural saline treatment (saline control), crush injury with subcutaneous pregabalin treatment (systemic drug control), and sham surgery (sham surgery control). Animals received either continuous infusions of 1% pregabalin for 7 days (treatment and systemic control) or saline (saline control) and were tested for pain behaviors using incapacitance meter, guarding scores, and radiant heat withdrawal latency (Hargreaves method). Nerves were studied using histology and immunohistochemistry for α(2)δ-1 receptors thought to mediate the central analgesic action of pregabalin.

RESULTS

Treatment rats had significantly better guarding scores than systemic drug controls or saline controls (P < 0.0001) and had significantly better incapacitance scores than systemic drug controls and saline controls (P ≤ 0.001). Hargreaves method data showed hypoalgesia in all injured animals with no difference among injured groups (P = 0.80). Qualitatively, immunohistochemistry likely showed equivalent expression of the α(2)δ-1 calcium channel at the injured nerve site in all nerve-injured animals.

CONCLUSIONS

Perineural pregabalin administration produced superior analgesia compared with that of systemic pregabalin in this neuropathic pain model. Perineural pregabalin treatment may provide a useful alternative to systemic pregabalin treatment for neuropathic pain.

Opioid Use, Satisfaction, and Pain Intensity After Orthopedic Surgery

BACKGROUND

Patients in other countries use fewer opioids than patients in the United States with satisfactory pain relief.

OBJECTIVE

This study tested the null hypothesis that opioid intake after orthopedic surgery does not influence satisfaction with pain management.

METHODS

A total of 232 orthopedic surgical inpatients completed measures of pain self-efficacy and symptoms of depression at enrollment and commonly used measures of pain intensity, satisfaction with pain relief, and satisfaction with hospital staff attention to pain approximately 14 days after surgery. Inpatient opioid intake per 24-hour period was quantified.

RESULTS

At a phone evaluation approximately 2 weeks after discharge from the hospital, patients who were always satisfied with their pain relief in hospital and always satisfied with staff attention to pain used significantly less opioids on day 1 compared with patients who were not always satisfied. There were no differences in satisfaction by type of surgery. The final multivariable model for not always satisfied with pain relief included greater opioid use on day 1 (odds ratio = 1.2), and preadmission diagnosis of depression (odds ratio = 2.6). Greater opioid use on day 1 was the only factor associated with less than always satisfied with the staff attention to pain relief (odds ratio = 1.3).

CONCLUSIONS

Patients who take more opioids report less satisfaction with pain relief and greater pain intensity. Evidence-based interventions to increase self-efficacy merit additional study for the management of postoperative pain.

LEVEL OF EVIDENCE

Prognostic, Level 1.

Update on neuropathic pain treatment: ion channel blockers and gabapentinoids

Neuropathic pain is a debilitating chronic pain condition, which remains difficult to treat. The current mainstays of treatment include physical therapy, interventional procedures and medications. Among medications, ion channel blockers and gabapentinoids are the 2 classes of drugs commonly used to treat neuropathic pain. It has been suggested that these medications may be useful to treat a variety of neuropathic pain conditions. This article provides several updates on the utility of both ion channel blockers and gabapentinoids for the treatment of neuropathic pain.