EFNS guidelines on pharmacological treatment of neuropathic pain

Evidence-Based Guidelines on the Use of Opioids in Chronic Non-Cancer Pain—A Consensus Statement by the Pain Association of Singapore Task Force

Introduction: While opioids are effective in carefully selected patients with chronic non-cancer pain (CNCP), they are associated with potential risks. Therefore, treatment recommendations for the safe and effective use of opioids in this patient population are needed. Materials and Methods: A multidisciplinary expert panel was convened by the Pain Association of Singapore to develop practical evidence-based recommendations on the use of opioids in the management of CNCP in the local population. This article discusses specific recommendations for various common CNCP conditions. Results: Available data demonstrate weak evidence for the long-term use of opioids. There is moderate evidence for the short-term benefit of opioids in certain CNCP conditions. Patients should be carefully screened and assessed prior to starting opioids. An opioid treatment agreement must be established, and urine drug testing may form part of this agreement. A trial duration of up to 2 months is necessary to determine efficacy, not only in terms of pain relief, but also to document improvement in function and quality of life. Regular reviews are essential with appropriate dose adjustments, if necessary, and routine assessment of analgesic efficacy, aberrant behaviour and adverse effects. The reasons for discontinuation of opioid therapy include side effects, lack of efficacy and aberrant drug behaviour. Conclusion: Due to insufficient evidence, the task force does not recommend the use of opioids as first-line treatment for various CNCP. They can be used as second- or third-line treatment, preferably as part of a multimodal approach. Additional studies conducted over extended periods are required. Key words: Chronic pain, Consensus statement, Guidelines, Non-cancer pain, Opioids

Cryptogenic sensory polyneuropathy

Chronic sensory or sensorimotor polyneuropathy is a common cause for referral to neurologists. Despite extensive diagnostic testing, up to one-third of these patients remain without a known cause, and are referred to as having cryptogenic sensory peripheral neuropathy. Symptoms progress slowly. On examination, there may be additional mild toe flexion and extension weakness. Electrophysiologic testing and histology reveals axonal neuropathy. Prognosis is usually favorable, as most patients maintain independent ambulation. Besides patient education and reassurance, management is focused on pharmacotherapy for neuropathic pain and physical therapy for balance training, and, occasionally, assistive devices.

Psychologic and biologic factors associated with fatigue in patients with persistent radiculopathy

Fatigue is a common symptom associated with neuropathic pain (NP) and can have negative consequences on psychosocial functioning, physical endurance, and quality of life. Recent evidence indicates that immune activation modulated through the increased release of proinflammatory cytokines can predict fatigue in some patient populations. Although earlier studies have shown that immune activation is a pathophysiologic feature of NP, there have been no studies to examine the relationship between immune activation and fatigue in persons with NP. Therefore, the purpose of this exploratory study was to: 1) determine the relationships among fatigue, pain, psychosocial factors, and selected biologic markers of immune activation (interleukin [IL] 6 and soluble IL-6 receptor [sIL-6R]) in participants with persistent radiculopathy; and 2) determine the differences in these variables based on fatigue severity. Participants (n = 80) were classified according to their level of fatigue as low (27.5%), moderate (32.5%), or high (40%), and significant differences were found between fatigue categories (p = .001). Multivariate analyses of variance revealed that individuals with moderate to high levels of fatigue differed from those with the lowest levels of fatigue in psychologic distress, depressive symptoms, IL-6, and sIL-6R, whereas the differences between moderate and high levels of fatigue were significant for psychologic distress and sIL-6R only. The findings suggest that immune activation affects fatigue severity and possibly other behavioral responses, offering important information when providing care to patients with persistent radiculopathy. The integration of biobehavioral nursing interventions in pain management may have a greater impact on quality of life than treatment focused only on pain.

An observational descriptive study of the epidemiology and treatment of neuropathic pain in a UK general population

Background

This study updated our knowledge of UK primary care neuropathic pain incidence rates and prescribing practices.

Methods

Patients with a first diagnosis of post-herpetic neuralgia (PHN), painful diabetic neuropathy (PDN) or phantom limb pain (PLP) were identified from the General Practice Research Database (2006 – 2010) and incidence rates were calculated. Prescription records were searched for pain treatments from diagnosis of these conditions and the duration and daily dose estimated for first-line and subsequent treatment regimens. Recording of neuropathic back and post-operative pain was investigated.

Results

The study included 5,920 patients with PHN, 5,340 with PDN, and 185 with PLP. The incidence per 10,000 person-years was 3.4 (95% CI 3.4, 3.5) for PHN; and 0.11 (95% CI 0.09, 0.12) for PLP. Validation of the PDN case definition suggested that was not sensitive. Incident PHN increased over the study period. The most common first-line treatments were amitriptyline or gabapentin in the PDN and PLP cohorts, and amitriptyline or co-codamol (codeine-paracetamol) in PHN. Paracetamol, co-dydramol (paracetamol-dihydrocodeine) and capsaicin were also often prescribed in one or more condition. Most first-line treatments comprised only one therapeutic class. Use of antiepileptics licensed for neuropathic pain treatment had increased since 2002–2005. Amitriptyline was the only antidepressant prescribed commonly as a first-line treatment.

Conclusion

The UK incidence of diagnosed PHN has increased with the incidence of back-pain and post-operative pain unclear. While use of licenced antiepileptics increased, prescribing of therapy with little evidence of efficacy in neuropathic pain is still common and consequently treatment was often not in-line with current guidance.

The journey to chronic pain: a grounded theory of older adults' experiences of pain associated with leg ulceration

This study aimed to develop a grounded theory to describe and explain the experience of pain and its impact, as reported by the individuals who had pain associated with chronic leg ulceration. The Strauss and Corbin grounded theory approach was used. In-depth interviews were undertaken with 11 people aged ≥ 65 years from Leeds in the north of England. All participants were cared for by home care nurses and had painful leg ulceration. The emergent grounded theory centered on a core category of "The journey to chronic pain." The theory suggested a trajectory consisting of three phases that the patient experiences, where the end result is a chronic pain syndrome. In phase 1, leg ulcer pain has predominantly acute nociceptive properties, and if this is not managed effectively, or ulcers do not heal, persistent pain may develop with both nociceptive and neuropathic properties (i.e., phase 2). If phase 2 pain is not managed effectively, patients may then develop refractory long-term pain (phase 3). Those who progress to phase 3 tend to experience negative consequences such as insomnia, depression, and suicidal ideation. Only when health care professionals understand and acknowledge the persistent and long-term nature of the pain in this patient group can the pain be managed effectively.

Pharmacokinetics, efficacy, and tolerability of a once-daily gastroretentive dosage form of gabapentin for the treatment of postherpetic neuralgia

Neurontin®, an immediate-release (IR) formulation of gabapentin, was the first drug approved by the United States Food and Drug Administration for the treatment of postherpetic neuralgia (PHN). The effective dosing regimen of gabapentin IR (G-IR) for PHN is 1800 mg/day in three divided doses. In 2011, a gastroretentive (GR) formulation of gabapentin (G-GR, Gralise®) was approved for the treatment of PHN. The effective dosing regimen of G-GR is 1800 mg, once daily taken with the evening meal. Compared with G-IR, G-GR has an apparently better tolerability profile with a 1-2 weeks shorter titration period to reach the same therapeutically effective dose. The differences in the dosing frequency and tolerability between G-IR and GR are mainly because of the difference in formulations and thus pharmacokinetic properties. The GR formulation takes advantage of normal human gastrointestinal (GI) physiology and the unique pharmacokinetic properties of gabapentin. In this review, we compare the IR and GR formulations of gabapentin, overview the GI physiology and GR mechanism of G-GR, and describe the unique pharmacokinetic properties of gabapentin. The effect of GR formulation on efficacy and the incidence of adverse events that are commonly associated with G-IR treatment in PHN patients are also discussed.

Survey on the treatment of postherpetic neuralgia in Korea; multicenter study of 1,414 patients

Background

Postherpetic neuralgia (PHN) is a serious complication resulting from herpes zoster infections, and it can impair the quality of life. In order to relieve pain from PHN, various treatments, including pharmacological and interventional methods have been used. However, little information on the recommendations for the interventional treatment of PHN, along with a lack of nation-wide surveys on the current status of PHN treatment exists. This multicenter study is the first survey on the treatment status of PHN in Korea.

Methods

Retrospective chart reviews were conducted on the entire patients who visited the pain clinics of 11 teaching hospitals from January to December of 2011. Co-morbid disease, affected site of PHN, routes to pain clinic visits, parenteral/topical medications for treatment, drugs used for nerve block, types and frequency of nerve blocks were investigated.

Results

A total of 1,414 patients' medical records were reviewed. The most commonly affected site was the thoracic area. The anticonvulsants and interlaminar epidural blocks were the most frequently used pharmacological and interventional methods for PHN treatment. For the interval of epidural block, intervals of 5 or more-weeks were the most popular. The proportion of PHN patients who get information from the mass media or the internet was only 0.8%.The incidence of suspected zoster sine herpete was only 0.1%.

Conclusions

The treatment methods for PHN vary among hospitals. The establishment of treatment recommendation for PHN treatment is necessary. In addition, public relations activities are required in order to inform the patients of PHN treatments by pain clinicians.

Influence of anatomic location of lidocaine patch 5% on effectiveness and tolerability for postherpetic neuralgia

PURPOSE

Lidocaine patch 5% is recommended as a first-line therapy for postherpetic neuralgia pain in neuropathic pain guidelines. Postherpetic neuralgia can occur anywhere on the body but often follows acute herpes zoster occurring in trigeminal and brachial plexus dermatomes. An analysis was conducted to determine whether the anatomic location of lidocaine patch 5% is associated with variations in effectiveness or tolerability in patients with postherpetic neuralgia.

METHODS

This was a post hoc analysis by anatomic site of patch placement (head [including neck], trunk [chest, abdomen, back, hips], and extremities [arm, leg]) of a 4-week, multicenter, open-label study that enrolled patients with persistent pain following herpes zoster infection. Effectiveness was measured by Brief Pain Inventory (BPI) average pain intensity (0 [no pain] to 10 [worst imaginable pain]) and the BPI subscale for pain relief (0% [no relief] to 100% [complete relief]). Tolerability was assessed on the basis of patient-reported adverse events.

RESULTS

Of 332 enrolled patients (59.6% women [n = 198]; 92.5% white [n = 307]; mean [standard deviation] age, 71.2 [13.9] years), those (n = 203) who applied lidocaine patch 5% to a single anatomic site only and had baseline and postbaseline pain score data were analyzed (trunk, n = 130; head, n = 41; extremities, n = 32). The frequency of adverse events differed significantly by anatomic location, with significantly more adverse events reported with patch placement on the head versus the extremities (P = 0.006) or trunk (P = 0.02). BPI average pain improved significantly from baseline in each of the three anatomic areas (mean score decrease, 1.50-2.04; P ≤ 0.002), with no significant difference in effectiveness by patch location.

CONCLUSION

Lidocaine 5% patch was effective and generally well tolerated for each anatomic area evaluated, although application to the head was tolerated less well compared with the trunk and extremities.

Efficacy of traditional Japanese herbal medicines-Keishikajutsubuto (TJ-18) and Bushi-matsu (TJ-3022)-against postherpetic neuralgia aggravated by self-reported cold stimulation: a case series

OBJECTIVES

It has been reported that postherpetic neuralgia (PHN) in patients over 60 years of age is aggravated under cold stimulation and is often difficult to treat. Keishikajutsubuto (TJ-18) and Bushi-matsu (TJ-3022) are traditional Japanese herbal medicines and have long been used to treat neuralgia and arthralgia, which are aggravated following cold stimulation. This study was designed to evaluate the effectiveness of combined TJ-18 and TJ-3022 therapy in cases of PHN aggravated by self-reported cold stimulation.

DESIGN

Fifteen (15) PHN patients aged 60 years and over were examined. Patients were aware of the persistent pain despite other treatments; pain was generally aggravated following exposure to cold stimulation. First, TJ-18 (7.5 g/day) was administered to patients, and then TJ-3022 (1.0 g/day) was also administered and progressively increased by 0.5-1.0 g increments every 2-4 weeks, until stable improvement was achieved, which was rated using the visual analogue scale (VAS). Analgesic effects were evaluated using the VAS during each patient visit.

OUTCOME MEASURES

Background variables, responses to treatment (time course of VAS rating, VAS improvement rate), the amount of additional TJ-3022 administered, and adverse reactions were analyzed.

RESULTS

Twelve (12) of the 15 patients completed the entire trial. Patient ages were 61-85 years, the male-to-female ratio was 4:8, and length of time after onset of herpes zoster was 2-92 months. In 3 patients, oral TJ-18 treatment was not possible due to hot flash or gastric discomfort. The VAS improvement rate for patients being orally administered both TJ-18 and TJ-3022 was 76.5±27.7% (mean±standard deviation). The additional TJ-3022 dose was 1.0-5.0 g/day. Twelve (12) patients have been treated without serious adverse reactions.

CONCLUSIONS

TJ-18 and TJ-3022 combination treatment is a promising means of treating intractable PHN, which has a self-reported tendency to aggravate pain under cold stimulation.

Cost analysis of adding pregabalin or gabapentin to the management of community-treated patients with peripheral neuropathic pain

OBJECTIVE

To compare the cost of adding either pregabalin or gabapentin to the management of community-treated patients with peripheral neuropathic pain (PNP).

METHODS

A retrospective observational study was conducted using medical records from a Spanish health care provider claims database. Patients receiving health care for PNP, above 18 years and for which either pregabalin or gabapentin was initiated between 2006 and 2008 were included. Economic evaluation included health care resource utilization costs and costs due to sick leave.

RESULTS

A total of 1163 patients with PNP were eligible for analysis: 764 were prescribed pregabalin and 399 gabapentin in addition to current pain therapy. Mean age was 59.2 years and 62.2% were female. Concomitant use of analgesics was higher in the gabapentin cohort (3.2 vs. 2.7; P = 0.003), mainly due to non-steroidal anti-inflammatory drugs (74.9% vs. 69.5%; P = 0.018) and opioids (27.7% vs. 17.9%; P = 0.031). Adjusted total costs per patient was lower in pregabalin-treated patients (€2514 vs. €3241; P = 0.003), due to less sick leave (€1067 vs. €1633; P = 0.018) and lower health care costs (€1447 vs. €1609; P = 0.004). The higher acquisition cost of pregabalin (€351 vs. €191; P < 0.001) was largely compensated with lower costs in medical visits, physiotherapy, hospital stays and concomitant analgesics.

CONCLUSIONS

In community-treated patients with PNP, total costs were considerably less for those patients initiated with pregabalin therapy than for those patients starting gabapentin add-on therapy. The relatively higher treatment acquisition cost of pregabalin was largely compensated by the overall lower costs for the other components of health care resources and sick leave, thus reducing the economic impact on the health care provider's budget and society.

Disturbance of consciousness and involuntary movements caused by pregabalin

A 91-year-old man with chronic low-back pain presented with 1-day history of disturbance of consciousness and myoclonus of all of his extremities and face. Laboratory examinations revealed no abnormalities. Administration of benzodiazepine for the myoclonus resulted in immediate and complete disappearance of the symptoms. He recently started taking pregabalin (Lyrica capsules) which was prescribed for low-back pain 3 days ago. The day following admission, he discontinued pregabalin. He did not experience recurrence of his symptoms any more. We concluded that the neurological symptoms he experienced were possibly due to pregabalin.

Post-herpetic neuralgia

Background

In spite of the large body of evidence available in the literature, definition and treatment of Post-Herpetic Neuralgia (PHN) are still lacking a consistent and universally recognized standardization. Furthermore, many issues concerning diagnosis, prediction and prevention of PHN need to be clarified in view of recent contributions.

Objectives

To assess whether PHN may be better defined, predicted, treated and prevented in light of recent data, and whether available alternative or adjunctive therapies may improve pain relief in treatment recalcitrant PHN.

Methods

Systematic reviews, meta-analyses, randomized controlled trials, cohort studies and protocols were searched; the search sources included PubMed, Cochrane Library, NICE, and DARE. More than 130 papers were selected and evaluated.

Results

Diagnosis of PHN is essentially clinical, but it can be improved by resorting to the many tools available, including some practical and accessible questionnaires. Prediction of PHN can be now much more accurate, taking into consideration a few well validated clinical and anamnestic variables. Treatment of PHN is presently based on a well characterized array of drugs and drug associations, including, among others, tricyclic antidepressants, gabapentinoids, opioids and many topical formulations. It is still unsatisfactory, however, in a substantial proportion of patients, especially those with many comorbidities and intense pain at herpes zoster (HZ) presentation, so that this frequent complication of HZ still strongly impacts on the quality of life of affected patients.

Conclusion

Further efforts are needed to improve the management of PHN. Potentially relevant interventions may include early antiviral therapy of acute HZ, prevention of HZ by adult vaccination, as well as new therapeutic approaches for patients experiencing PHN.

Differential effects of peripheral versus central coadministration of QX-314 and capsaicin on neuropathic pain in rats

BACKGROUND

Neuropathic pain is common and difficult to treat. Recently a technique was developed to selectively inhibit nociceptive inputs by simultaneously applying two drugs: capsaicin, a transient receptor potential vanilloid receptor-1 channel activator, and QX-314, a lidocaine derivative that intracellularly blocks sodium channels. We used this technique to investigate whether transient receptor potential vanilloid receptor 1-expressing nociceptors contribute to neuropathic pain.

METHODS

The rat chronic constriction injury model was used to induce neuropathic pain in order to test the analgesic effects of both peripheral (perisciatic) and central (intrathecal) administration of the QX-314/capsaicin combination. The Hargreaves and von Frey tests were used to monitor evoked pain-like behaviors and visual observations were used to rank spontaneous pain-like behaviors.

RESULTS

Perisciatic injections of the QX-314/capsaicin combination transiently increased the withdrawal thresholds by approximately 3-fold, for mechanical and thermal stimuli in rats (n = 6/group) with nerve injuries suggesting that peripheral transient receptor potential vanilloid receptor 1-expressing nociceptors contribute to neuropathic pain. In contrast, intrathecal administration of the QX-314/capsaicin combination did not alleviate pain-like behaviors (n = 5/group). Surprisingly, intrathecal QX-314 alone (n = 9) or in combination with capsaicin (n = 8) evoked spontaneous pain-like behaviors.

CONCLUSIONS

Data from the perisciatic injections suggested that a component of neuropathic pain was mediated by peripheral nociceptive inputs. The role of central nociceptive terminals could not be determined because of the severe side effects of the intrathecal drug combination. We concluded that only peripheral blockade of transient receptor potential vanilloid receptor 1-expressing nociceptive afferents by the QX-314/capsaicin combination was effective at reducing neuropathic allodynia and hyperalgesia.

Recent advances in the pharmaceutical management of pain

Pain is an unpleasant sensory and emotional experience for patients. Management of pain is the most frequent issue encountered by clinicians and treatment is usually with pharmacological therapy. This review discusses recent pharmaceutical advances in pain management with respect to new modes of analgesic delivery, as well as new analgesic agents and adjuvants that are currently being investigated for their analgesic properties. New modes of administration include transdermal delivery in the form of skin patches, transmucosal delivery, inhalational administration, various patient-controlled devices and extended-release analgesic formulations. Up-to-date research is presented on classical analgesics, such as opioids, anti-inflammatory agents, including cyclo-oxygenase-2 inhibitors and paracetamol (acetaminophen), local anesthetics and ketamine. In addition, newer agents such as antidepressants and antiepileptic drugs as well as medicinal cannabinoids are discussed. As our understanding of the multiple pain pathways involved in the pathogenesis of pain expands, further compounds with analgesic properties will be developed.

Treatment of neuropathic pain with 5% lidocaine-medicated plaster: Five years of clinical experience

BACKGROUND

Neuropathic pain is often severe and adversely affects patients' quality of life.

OBJECTIVE

To perform a retrospective, observational study investigating the efficacy and safety of treating refractory chronic neuropathic pain with 5% lidocaine-medicated plaster, in patients attending pain centres.

METHODS

Medical records from 467 patients treated with 5% lidocaine-medicated plaster were evaluated for efficacy (maximum and minimum pain intensities and coanalgesic consumption) and adverse events. Data from an initial assessment and at least one follow-up visit had to be available, and separate analyses were conducted for the general population and the subpopulation older than 70 years of age.

RESULTS

Of the patients enrolled, 25.0% were older than 70 years of age. While 20.6% had postherpetic neuralgia, 76.3% had other types of peripheral pain. Approximately 78.1% of cases of peripheral neuropathic pain followed surgery, and 23% were post-traumatic pain. The time from onset to referral was more than one year in two- thirds of cases. All patients experienced pain of at least moderate severity (mean [± SD] 11-point numerical rating scale score 5.2 ± 2.4 to 8.2 ± 1.6). Treatment with 5% lidocaine-medicated plaster reduced pain intensity by more than 50% in 45.5% of patients, and by at least 30% in 82.2%. Of note, the consumption of analgesics and coanalgesics was significantly reduced. Results were similar in both the general population and the subpopulation older than 70 years of age, at high risk and often receiving multiple medications.

CONCLUSIONS

Treatment of refractory neuropathic pain with 5% lidocaine-medicated plaster clearly demonstrated efficacy and an excellent safety profile in patients with refractory neuropathic pain.

A cost-effectiveness analysis of the effect of pregabalin versus usual care in the treatment of refractory neuropathic pain in routine medical practice in Spain

OBJECTIVE

The objective of this study was to estimate the cost-effectiveness of pregabalin vs usual care (UC) in outpatients with refractory neuropathic pain (NeP), treated according to routine medical practice in primary care settings in Spain.

METHODS

Patients were extracted from a 12-week noninterventional prospective study conducted to ascertain the costs of NeP. Pairs of pregabalin-naïve patients receiving UC or pregabalin, matched by age, gender, pain intensity, and refractory to previous treatment, were selected in a 1:1 ratio. Refractory was considered a patient with actual pain (scoring >40 in a 100 mm in a pain visual analog scale) after receiving a course of a standard analgesic, at its recommended doses. Perspectives of the Spanish National Healthcare System and society were included in the analysis. Effectiveness was expressed as quality-adjusted life-year (QALY) gain. Results of the cost-effectiveness analysis were expressed as an incremental cost per QALY (ICER) gained. Probabilistic sensitivity analysis using bootstrapping techniques was also carried out.

RESULTS

A total of 160 pairs were extracted. Compared with UC, pregabalin was associated with significantly higher QALY gain; 0.0374 ± 0.0367 vs 0.0224 ± 0.0313 (P < 0.001). Despite drug acquisition costs being higher for pregabalin (€251 ± 125 vs €104 ± 121; P < 0.001), total and health care costs incurred for pregabalin were similar in both groups; €1,335 ± 1,302 vs €1,387 ± 1,489 (P = 0.587) and €529 ± 438 vs €560 ± 672 (P = 0.628), respectively, yielding a dominant ICER for both total and health care costs in the base case scenario; 95% confidence intervals, respectively, dominant to €17,268, and dominant to €6,508. Sensitivity analysis confirmed results of the basecase scenario.

CONCLUSION

This study showed that pregabalin may be cost-effective in the treatment of refractory NeP patients when compared with UC in routine medical practice in Spain.

Tramadol/paracetamol fixed-dose combination in the treatment of moderate to severe pain

Pain is the most common reason patients seek medical attention and pain relief has been put forward as an ethical obligation of clinicians and a fundamental human right. However, pain management is challenging because the pathophysiology of pain is complex and not completely understood. Widely used analgesics such as nonsteroidal anti-inflammatory drugs (NSAIDs) and paracetamol (acetaminophen) have been associated with adverse events. Adverse event rates are of concern, especially in long-term treatment or at high doses. Paracetamol and NSAIDs are available by prescription, over the counter, and in combination preparations. Patients may be unaware of the risk associated with high dosages or long-term use of paracetamol and NSAIDs. Clinicians should encourage patients to disclose all medications they take in a “do ask, do tell” approach that includes patient education about the risks and benefits of common pain relievers. The ideal pain reliever would have few risks and enhanced analgesic efficacy. Fixed-dose combination analgesics with two or more agents may offer additive or synergistic benefits to treat the multiple mechanisms of pain. Therefore, pain may be effectively treated while toxicity is reduced due to lower doses. One recent fixed-dose combination analgesic product combines tramadol, a centrally acting weak opioid analgesic, with low-dose paracetamol. Evidence-based guidelines recognize the potential value of combination analgesics in specific situations. The current guideline-based paradigm for pain treatment recommends NSAIDs for ongoing use with analgesics such as opioids to manage flares. However, the treatment model should evolve how to use low-dose combination products to manage pain with occasional use of NSAIDs for flares to avoid long-term and high-dose treatment with these analgesics. A next step in pain management guidelines should be targeted therapy when possible, or low-dose combination therapy or both, to achieve maximal efficacy with minimal toxicity.

Management of painful diabetic neuropathy: guideline guidance or jungle?

The treatment of painful diabetic polyneuropathy (PDPN) remains a major challenge. A number of reasons have made the guidelines on PDPN management of particular interest, including its high prevalence, health and socioeconomic impact, interdisciplinary nature and the need for updated evidence-based information to refine patient-tailored treatment by weighing up the risks of each treatment against its proven benefits, as well as optimizing the use of all available resources. The various guidelines on the management of neuropathic pain developed so far contain some differences in their work methodology and results. Some variations in the recommendations are to be expected but could be disorienting and confusing for stakeholders. In this review, a critical evaluation of the more recent guidelines on the management of PDPN is provided together with highlights on points of agreement and disagreement as well as insights into their clinical aspects.

Clinical development of a once-daily gastroretentive formulation of gabapentin for treatment of postherpetic neuralgia: an overview

INTRODUCTION

Gabapentin immediate-release formulations (G-IR) administered three times a day is an efficacious treatment for postherpetic neuralgia (PHN), but its potential benefits may not be fully realized due to tolerability issues as well as its pharmacokinetic (PK) properties such as its short half-life, and regional and saturable absorption in the proximal small intestine. The gastroretentive once-daily formulation of gabapentin (G-GR) allows for less frequent dosing while maintaining efficacy and may also reduce adverse events (AEs) associated with high plasma concentration of gabapentin occurring during the waking hours. G-GR slowly releases the drug from the tablet to the upper small intestine, where gabapentin is best absorbed, over approximately 10 h.

AREA COVERED

This report reviews the development of the gastroretentive technology used in the once-daily formulation of gabapentin (G-GR), and describes the clinical development of G-GR from PK studies through the Phase III efficacy and safety studies, with comparisons made with G-IR.

EXPERT OPINION

The technology takes advantage of the normal physiology of the stomach in the fed state to provide gastroretention, which in turn allows for gradual release of the active ingredient over several hours to the small intestine where gabapentin is best absorbed. The GR technology used in G-GR resulted in a decreased dosing frequency from three times per day for the IR product to once daily in the treatment of PHN, while maintaining the same efficacy with an apparent reduced incidence of AEs common to G-IR therapy.

Acute augmentation of epoxygenated fatty acid levels rapidly reduces pain-related behavior in a rat model of type I diabetes

The nerve damage occurring as a consequence of glucose toxicity in diabetes leads to neuropathic pain, among other problems. This pain dramatically reduces the quality of life in afflicted patients. The progressive damage to the peripheral nervous system is irreversible although strict control of hyperglycemia may prevent further damage. Current treatments include tricyclic antidepressants, anticonvulsants, and opioids, depending on the severity of the pain state. However, available therapeutics have drawbacks, arguing for the need to better understand the pathophysiology of neuropathic pain and develop novel treatments. Here we demonstrate that stabilization of a class of bioactive lipids, epoxygenated fatty acids (EpFAs), greatly reduces allodynia in rats caused by streptozocin-induced type I diabetes. Inhibitors of the soluble epoxide hydrolase (sEHI) elevated and stabilized the levels of plasma and spinal EpFAs, respectively, and generated dose-dependent antiallodynic effects more potently and efficaciously than gabapentin. In acute experiments, positive modulation of EpFAs did not display differences in insulin sensitivity, glucose tolerance, or insulin secretion, indicating the efficacy of sEHIs are not related to the glycemic status. Quantitative metabolomic analysis of a panel of 26 bioactive lipids demonstrated that sEHI-mediated antiallodynic effects coincided with a selective elevation of the levels of EpFAs in the plasma, and a decrease in degradation products coincided with the dihydroxy fatty acids in the spinal cord. Overall, these results argue that further efforts in understanding the spectrum of effects of EpFAs will yield novel opportunities in treating neuropathic pain.

Review of the history and current status of cell-transplant approaches for the management of neuropathic pain

Treatment of sensory neuropathies, whether inherited or caused by trauma, the progress of diabetes, or other disease states, are among the most difficult problems in modern clinical practice. Cell therapy to release antinociceptive agents near the injured spinal cord would be the logical next step in the development of treatment modalities. But few clinical trials, especially for chronic pain, have tested the transplant of cells or a cell line to treat human disease. The history of the research and development of useful cell-transplant-based approaches offers an understanding of the advantages and problems associated with these technologies, but as an adjuvant or replacement for current pharmacological treatments, cell therapy is a likely near future clinical tool for improved health care.

Impairment of GABAB receptor dimer by endogenous 14-3-3ζ in chronic pain conditions

In the central nervous system, the inhibitory GABAB receptor is the archetype of heterodimeric G protein-coupled receptors (GPCRs). However, the regulation of GABAB dimerization, and more generally of GPCR oligomerization, remains largely unknown. We propose a novel mechanism for inhibition of GPCR activity through de-dimerization in pathological conditions. We show here that 14-3-3ζ, a GABAB1-binding protein, dissociates the GABAB heterodimer, resulting in the impairment of GABAB signalling in spinal neurons. In the dorsal spinal cord of neuropathic rats, 14-3-3ζ is overexpressed and weakens GABAB inhibition. Using anti-14-3-3ζ siRNA or competing peptides disrupts 14-3-3ζ/GABAB1 interaction and restores functional GABAB heterodimers in the dorsal horn. Importantly, both strategies greatly enhance the anti-nociceptive effect of intrathecal Baclofen in neuropathic rats. Taken together, our data provide the first example of endogenous regulation of a GPCR oligomeric state and demonstrate its functional impact on the pathophysiological process of neuropathic pain sensitization.

CYP2D6*4 polymorphism, tramadol treatment and its clinical impact in patients with postherpetic neuralgia

Aim: The aim of this study was to investigate the associations between the CYP2D6*4 polymorphism, interindividual differences in CYP2D6 activity and adverse drug effects in postherpetic neuralgia (PHN) patients receiving tramadol. Patients & methods: The study comprised 158 patients (including 78 nonresponders and 80 responders) with PHN who were undergoing analgesic treatment at the Pain Clinic in the Out Patient Department of the University College of Medical Sciences, Guru Teg Bahadur Hospital (New Delhi, India). The numerical rating scale scores were measured at the resting and movement stages; Neuropathic Pain Symptom Inventory scores were evaluated by the treating physician. WHO-brief questionnaire scores for quality of life and adverse drug effects during the time of study were recorded. All samples were analyzed for the CYP2D6*4 polymorphism using the PCR-restriction fragmentation length polymorphism method. Results: The genotype distribution did not vary significantly among different age groups in nonresponders and responders. The CYP2D6*4 polymorphism was significantly associated with lower Neuropathic Pain Symptom Inventory (burning, squeezing stabbing and pressure) scores. The quality-of-life (sociological, psychological and environmental domains) scores correlated with CYP2D6*4 and showed significant results (p < 0.05) using a generalized linear model. No association was found between the physiological domain compared with the CYP2D6*4 allele (p > 0.05). In addition, the homozygous mutated CYP2D6*4 allele was not related to adverse effects of analgesic therapy. Conclusion: The CYP2D6*4 polymorphism may not be a predictor for treatment outcome of patients with PHN receiving tramadol. However, further investigation is required to confirm these findings in a larger sample size.

Diabetic neuropathy: clinical manifestations and current treatments

Diabetic peripheral neuropathy is a prevalent, disabling disorder. The most common manifestation is distal symmetrical polyneuropathy (DSP), but many patterns of nerve injury can occur. Currently, the only effective treatments are glucose control and pain management. While glucose control substantially decreases the development of neuropathy in those with type 1 diabetes, the effect is probably much smaller in those with type 2 diabetes. Evidence supports the use of specific anticonvulsants and antidepressants for pain management in patients with diabetic peripheral neuropathy. However, the lack of disease-modifying therapies for diabetic DSP makes the identification of new modifiable risk factors essential. Growing evidence supports an association between components of the metabolic syndrome, including prediabetes, and neuropathy. Studies are needed to further explore this association, which has implications for the development of new treatments for this common disorder.

Evidence-based guideline for neuropathic pain interventional treatments: spinal cord stimulation, intravenous infusions, epidural injections and nerve blocks

BACKGROUND

The Special Interest Group of the Canadian Pain Society has produced consensus-based guidelines for the pharmacological management of neuropathic pain. The society aimed to generate an additional guideline for other forms of neuropathic pain treatments.

OBJECTIVE

To develop evidence-based recommendations for neuropathic pain interventional treatments.

METHODS

A task force was created and engaged the Institute of Health Economics in Edmonton, Alberta, to survey the literature pertaining to multiple treatments. Sufficient literature existed on four interventions only: spinal cord stimulation; epidural injections; intravenous infusions; and nerve blocks. A comprehensive search was conducted for systematic reviews, randomized controlled trials and evidence-based clinical practice guidelines; a critical review was generated on each topic. A modified United States Preventive Services Task Force tool was used for quality rating and grading of recommendations.

RESULTS

Investigators reviewed four studies of spinal cord stimulation, 19 studies of intravenous infusions, 14 studies of epidural injections and 16 studies of nerve blocks that met the inclusion criteria. The task force chairs rated the quality of evidence and graded the recommendations. Feedback was solicited from the members of the task force.

CONCLUSION

There is sufficient evidence to support recommendations for some of these interventions for selected neuropathic pain conditions. This evidence is, at best, moderate and is often limited or conflicting. Pain practitioners are encouraged to explore evidence-based treatment options before considering unproven treatments. Full disclosure of risks and benefits of the available options is necessary for shared decision making and informed consent.

Utilization of antidepressants in Taiwan: a nationwide population-based survey from 2000 to 2009

OBJECTIVE

This study examined trends in antidepressant utilization in Taiwan between 2000 and 2009.

METHODS

We collected data from the National Health Insurance Research Database of all incident antidepressant use. We described the incidence, prevalence, and therapeutic indications of antidepressant use. We tested the trends by using logistic regression analyses with adjustment for age and sex.

RESULTS

Overall, the prevalence of antidepressant use per 1000 persons increased from 32.1 in 2000 to 46.3 in 2009; however, the incidence per 1000 persons declined from 20.8 in 2000 to 16.5 in 2009. For antidepressant classes, the prescriptions of selective serotonin reuptake inhibitors and other new agents increased during the study periods; however, the use of tricyclic antidepressants, trazodone, and monoamine oxidase inhibitors declined. For therapeutic indications, we found increasing trends of antidepressant use for sleep and adjustment disorders; however, the rates of antidepressant use for mood disorder, anxiety disorders, and non-psychiatric conditions decreased.

CONCLUSIONS

Regarding the new use of antidepressants in Taiwan between 2000 and 2009, we found that the decreased incidence of antidepressant use might be attributed mainly to the decreased use of tricyclic antidepressants and monoamine oxidase inhibitors. Decreased use among middle-aged and older persons and fewer antidepressant prescriptions for non-psychiatric conditions were also noted.

Prevalence and comorbidity of chronic pain in the German general population

The objectives of this study were to evaluate 1) the prevalence of chronic and neuropathic pain features (NeP); 2) their comorbidities with psychiatric disorders and organic diseases; and 3) their impact on daily life and health care utilization. A random sample of 3011 participants (≥15 years), representative of Germany, was interviewed by telephone. Chronic pain duration was set at three months. Neuropathy, frequency, severity, duration, impacts on functioning, and health care utilizations were investigated. Psychiatric disorders were assessed using DSM-IV-TR criteria. ICD-10 was used for organic diseases. Overall, 26.8% (95% confidence interval: 25.2-28.4%) of the sample reported having pain; 1.9% had acute pain (i.e., lasting less than three months), setting the prevalence of chronic pain at 24.9%. More precisely, 18.4% of the sample had non-neuropathic chronic pain (non-NeP) and 6.5% had NeP features. NeP presented several differences from non-NeP: individuals NeP features reported higher pain severity and higher interference of pain in daily activities compared to the non-NeP group. Individuals suffering from a major depressive disorder were three times more likely to have non-NeP and six times more likely to have NeP features. Individuals with obesity, diabetes, hypertension, cerebrovascular diseases, diseases of the nervous system, and diseases of the blood and blood-forming organs were at higher risk of having NeP but not non-NeP. These differences in prevalence and comorbidities between non-NeP and NeP features show how important it is to regard these different modalities of pain separately. Participants with NeP features suffer more and have greater impairment in their daily life than those with non-NeP.

Diagnosis and treatment of pain in small-fiber neuropathy

Small-fiber neuropathy manifests in a variety of different diseases and often results in symptoms of burning pain, shooting pain, allodynia, and hyperesthesia. Diagnosis of small-fiber neuropathy is determined primarily by the history and physical exam, but functional neurophysiologic testing and skin biopsy evaluation of intraepidermal nerve-fiber density can provide diagnostic confirmation. Management of small-fiber neuropathy depends on the underlying etiology with concurrent treatment of associated neuropathic pain. A variety of recent guidelines proposes the use of antidepressants, anticonvulsants, opioids, topical therapies, and nonpharmacologic treatments as part of the overall management of neuropathic pain. Unfortunately, little data about the treatment of pain specifically in small-fiber neuropathy exist because most studies combine mixed neuropathic pain syndromes in the analysis. Additional studies targeting the treatment of pain in small-fiber neuropathy are needed to guide decision making.

Clinical characteristics and patterns of healthcare utilization in patients with painful neuropathic disorders in UK general practice: a retrospective cohort study

BACKGROUND

Clinical characteristics and patterns of healthcare utilization in patients with painful neuropathic disorders (PNDs) who are under the care of general practitioners (GPs) in the UK are not well understood.

METHODS

Using a large electronic UK database, we identified all adults (age ≥ 18 years) with any GP encounters between 1 January 2006-31 December 2006 at which a diagnosis of PND was noted ("PND patients"). An age-and gender-matched comparison group also was constituted consisting of randomly selected patients with one or more GP encounters-but no mention of PNDs-during this period. Characteristics and patterns of healthcare utilization of patients in the two groups were then examined over the one-year study period.

RESULTS

The study sample consisted of 31,688 patients with mention of PNDs and an equal number of matched comparators; mean age was 56 years, and 62% were women. The prevalence of various comorbidities was higher among patients in the PND group, including digestive disorders (31% vs. 17% for comparison group), circulatory disorders (29% vs. 22%), and depression (4% vs. 3%) (all p < 0.01). Receipt of prescriptions for pain-related pharmacotherapy also was higher among PND patients, including nonsteroidal anti-inflammatory drugs (56% of PND patients had one or more such prescriptions vs. only 22% in the comparison group), opioids (49% vs. 12%), tricyclic antidepressants (20% vs. 1%), and antiepileptics (12% vs. 1%) (all p < 0.01). PND patients also averaged significantly more GP visits (22.8 vs. 14.2) and referrals to specialists (2.8 vs. 1.4) over one year (both comparisons p < 0.01).

CONCLUSIONS

Patients with PNDs under the care of GPs in the UK have relatively high levels of use of healthcare services and pain-related pharmacotherapy.

Is treatment of postherpetic neuralgia in the community consistent with evidence-based recommendations?

Few studies have examined the extent to which treatment of patients with neuropathic pain in the community is consistent with evidence-based treatment recommendations. U.S. health care claims were used to identify patients who received a diagnosis of postherpetic neuralgia (PHN). The initial pharmacologic treatments and changes to these treatment regimens were categorized according to the International Association for the Study of Pain Neuropathic Pain Special Interest Group recommendations for first-, second-, and third-line treatment of neuropathic pain. The results indicated that the treatment of PHN was only partially consistent with these treatment recommendations. Of the patients diagnosed with PHN who were not already on a specified treatment, 70% began treatment with either a first-, second-, or third-line treatment or a not-recommended treatment, and 30% did not begin treatment with any of these medications. Only one-quarter of patients began treatment with a first-line medication, the same percentage that began treatment with either a third-line medication or a not-recommended treatment. There was a wide range of initial treatment durations, but the means and medians suggest that patients and clinicians often decide to change the initial treatment within 2 months, either by discontinuing it, replacing it with a new medication, or adding a new medication. Although there were generally shorter treatment durations with opioid analgesics and tramadol, these medications were more frequently used in beginning treatment than the other treatments. The results suggest that a considerable number of patients with PHN in the community are not receiving evidence-based treatment.

Duloxetine contributing to a successful multimodal treatment program for peripheral femoral neuropathy and comorbid 'reactive depression' in an adolescent

In the United States, duloxetine has been approved for the treatment of major depressive disorder, diabetic peripheral neuropathic pain and fibromyalgia in the adult population. Data regarding the use of duloxetine in the pediatric population, however, are very limited. Femoral nerve injury is a rare complication of cardiac catheterization. In the case described, duloxetine contributed to a successful multimodal treatment program for peripheral neuropathic pain due to femoral neuropathy in an adolescent with 'reactive depression' and conversion symptoms. To the best of the authors' knowledge, the present article is only the third such report on this dual use of duloxetine in children and adolescents, and the first report of such treatment following femoral neuropathy induced by cardiac catheterization.