Algorithm for neuropathic pain treatment: an evidence based proposal

Treatment of diabetic polyneuropathy: Update 2006

At least one of four diabetic patients is affected by distal symmetric polyneuropathy (DSP), which represents a major health problem, as it may present with partly excruciating neuropathic pain and is responsible for substantial morbidity, increased mortality, and impaired quality of life. Treatment is based on four cornerstones: (a) causal treatment aimed at (near)-normoglycemia, (b) treatment based on pathogenetic mechanisms, (c) symptomatic treatment, and (d) avoidance of risk factors and complications. Recent experimental studies suggest a multifactorial pathogenesis of diabetic neuropathy. From the clinical point of view it is important to note that, on the basis of these pathogenetic mechanisms, therapeutic approaches could be derived, some of which are currently being evaluated in clinical trials. Among these agents only alpha-lipoic acid is available for treatment in several countries and epalrestat in Japan. Although several novel analgesic drugs, such as duloxetine and pregabalin, have recently been introduced into clinical practice, the pharmacological treatment of chronic painful diabetic neuropathy remains a challenge for the physician. Individual tolerability remains a major aspect in any treatment decision. Epidemiological data indicate that not only increased alcohol consumption but also the traditional cardiovascular risk factors, such as hypertension, smoking, and visceral obesity, play a role in development and progression of diabetic neuropathy and, hence, need to be prevented or treated.

Emerging drugs in neuropathic pain

Neuropathic pain is a personally devastating and costly condition affecting 3-8% of the population. Existing treatments have limited effectiveness and produce relatively frequent adverse effects. Preclinical research has identified many promising pharmacological targets; however, reliable predictors of success in humans remain elusive. At least 50 new molecular entities have reached clinical development including: glutamate antagonists, cytokine inhibitors, vanilloid-receptor agonists, catecholamine modulators, ion-channel blockers, anticonvulsants, opioids, cannabinoids, COX inhibitors, acteylcholine modulators, adenosine receptor agonists and several miscellaneous drugs. Eight drugs are in Phase III trials at present. Strategies that may show promise over existing treatments include topical therapies, analgesic combinations and, in future, gene-related therapies. Recent years have heralded an explosion of pharmaceutical development in neuropathic pain, reflecting advanced knowledge of neurobiology and a heightened perception of the commercial value of neuropathic pain therapeutics. In the interest of improving patient care, the authors recommend implementing comparative studies throughout the development process in order to demonstrate the increased value of novel agents.

[Reproducible efficacy of tricyclic antidepressant on chronic pain in an elderly patient with osteoporosis]

An 81-year-old woman was admitted due to exacerbation of chronic back pain from a vertebral osteoporosis fracture. The lumbar MRI examination revealed compression fracture of Th12 and L1 bones. Initial treatment with roxoprofen, calcitonin, bupurenorfin, and morphine did not achieve pain reduction in the patient. Because her geriatric depression scale score was low, we next tried to treat the pain using an antidepressant. Although the pain was improved by amitriptyline, the side effects of dry mouth and urinary incontinence were occurred. Milnacipran, a serotonin and norepinephrine reuptake inhibitor (SNRI), was then tried for the treatment of the chronic pain instead of amitriptyline, but the pain was increased. Then, she was given amitriptyline again for treatment of the chronic back pain instead of SNRI. The second-time amitriptyline treatment was effective to reduce the pain, with minimal side-effects. Because chronic pain due to osteoporosis is often difficult to treat in elderly patients, the classic antidepressant, amitriptyline, may help pain control by narcotics and anti-inflammatory agents in some elderly patients.

Management of painful neuropathies

Inadequately assessed and poorly managed pain contributes both to high general medical cost and to increasing numbers of societal problems. A large determining factor of inadequate pain care is the lack of understanding about the complex nature of pain and of a rational approach to its assessment and treatment. The less than adequate assessment of neuropathic pain and its relatively poor response to typical analgesic medications are major determinants to the undertreatment of pain. Other than the important management concept of treating the underlying cause, current approaches to the treatment of pain in general, and neuropathic pain in particular, have shifted away from treatment of individual syndromes toward the identification and management of common symptoms and the mechanisms upon which such symptoms are presumed to be based. This article summarizes the features of neuropathic pain that commonly appear in most peripheral neuropathies, regardless of the mechanism of injury, and provides an approach for the selection of treatment.

Blocking sodium channels to treat neuropathic pain

Neuropathic pain remains a large unmet medical need. A number of therapeutic options exist, but efficacy and tolerability are less than satisfactory. Based on animal models and limited data from human patients, the pain and hypersensitivity that characterize neuropathic pain are associated with spontaneous discharges of normally quiescent nociceptors. Sodium channel blockers inhibit this spontaneous activity, reverse nerve injury-induced pain behavior in animals and alleviate neuropathic pain in humans. Several sodium channel subtypes are expressed primarily in sensory neurons and may contribute to the efficacy of sodium channel blockers. In this report, the authors review the current understanding of the role of sodium channels and of specific sodium channel subtypes in neuropathic pain signaling.

Sequential medication strategies for postherpetic neuralgia: a cost-effectiveness analysis

Several medications are recommended for relief of postherpetic neuralgia (PHN). A sequential treatment algorithm has been suggested, but its cost-effectiveness is unclear. We developed a decision model to estimate the cost-effectiveness of this algorithm compared with other sequential medication strategies in 70-year-olds with PHN, using literature data to model medication-related PHN relief while also accounting for severe medication side effects. Hypothetical patients with and without coronary artery disease (CAD) were considered separately, with and without localized pain. Sequential medication switches occurred as the result of inadequate relief or intolerable side effects. Probabilistic sensitivity analyses were performed to estimate the favorability of each medication early in treatment sequences. In patients without CAD, tricyclic and gabapentin were equally favored as initial therapy if mortality with tricyclic use was not increased, but gabapentin was strongly favored if it was. In patients with CAD, gabapentin was overwhelmingly favored. In either patient group, opioids, pregabalin, and tramadol were not favored as initial therapy but were sensible choices later in treatment sequences. The lidocaine patch was a reasonable first choice in patients with localized PHN. Our analysis supports the suggested treatment algorithm, with cost-effectiveness ratios within acceptable ranges for medications given sequentially, based on literature-based estimates of effectiveness and tolerability.

PERSPECTIVE

This article examines the cost-effectiveness of recommended sequential treatment strategies for postherpetic neuralgia. This decision analysis-based synthesis of effectiveness and cost data found that recommended treatment algorithms are also economically reasonable.

Salmon calcitonin in the treatment of post herpetic neuralgia

A 78-year-old man with severe chronic obstructive pulmonary disease presented to our pain medicine clinic for treatment of post herpetic neuralgia. Pharmacotherapy with tricyclic antidepressants, anticonvulsants, tramadol and traditional analgesics had failed, primarily due to adverse drug effects, particularly sedation, dizziness and nausea. Consequently, intravenous salmon calcitonin was administered, based on evidence of efficacy in the treatment of other neuropathic pain syndromes and its relatively benign side-effects profile. The patient reported immediate and sustained improvement in his post herpetic neuralgia for over two months, without adverse effects from the calcitonin therapy.

Randomized study of tramadol/acetaminophen versus placebo in painful diabetic peripheral neuropathy

OBJECTIVE

To examine the efficacy and safety of tramadol/acetaminophen (APAP) for the management of painful diabetic peripheral neuropathy (DPN).

METHODS

Adults with painful DPN involving the lower extremities received 37.5 mg tramadol/325 mg APAP or placebo, up to 1-2 tablets four times daily, for 66 days. Subjects rated average daily pain and sleep interference from 0 ('none') to 10 ('pain as bad as you can imagine' or 'complete interference') every night. Baseline values were recorded for 7 days before starting study medication. The primary endpoint was change in mean of average daily pain scores from baseline to final week. Secondary efficacy outcomes included pain intensity, sleep interference, quality of life, mood, and global impression of change. Potential study limitations included permission to use serotonin reuptake inhibitors concomitantly (except venlafaxine or duloxetine) and the lack of a tramadol-alone or APAP-alone control group.

RESULTS

A total of 160 subjects received tramadol/APAP and 153 received placebo. Tramadol/APAP reduced average daily pain significantly compared to placebo from baseline to the final week (-2.71 vs. -1.83, p = 0.001). Tramadol/APAP was associated with significantly greater improvement than placebo (p < or = 0.05) for all measures of pain intensity, sleep interference, and global impression, as well as several measures of quality of life and mood. The only adverse event reported by > 10% of subjects in either the tramadol/APAP or placebo group was nausea (11.9% and 3.3%, respectively). Adverse events resulted in early study discontinuation for 8.1% and 6.5% of subjects in the tramadol/APAP and placebo groups, respectively.

CONCLUSION

Tramadol/APAP was more effective than placebo and was well tolerated in the management of painful DPN.

Recommendations for the management of herpes zoster

The objective of this article is to provide evidence-based recommendations for the management of patients with herpes zoster (HZ) that take into account clinical efficacy, adverse effects, impact on quality of life, and costs of treatment. Systematic literature reviews, published randomized clinical trials, existing guidelines, and the authors' clinical and research experience relevant to the management of patients with HZ were reviewed at a consensus meeting. The results of controlled trials and the clinical experience of the authors support the use of acyclovir, brivudin (where available), famciclovir, and valacyclovir as first-line antiviral therapy for the treatment of patients with HZ. Specific recommendations for the use of these medications are provided. In addition, suggestions are made for treatments that, when used in combination with antiviral therapy, may further reduce pain and other complications of HZ.

Diabetic Painful Neuropathy

Diabetic painful neuropathy (DPN) is one of the most common causes of neuropathic pain. The management of DPN consists of excluding other causes of painful peripheral neuropathy, maximising diabetic control and using medications to alleviate pain. The precise relationship between glycaemic control and the development and severity of DPN remains controversial. In this context, drugs such as aldose reductase inhibitors, ACE inhibitors, lipid-lowering agents and alpha-lipoic acid (thioctic acid) may have a useful role to play. There is also evidence that a successful pancreatic transplant may improve symptoms over time, but the mainstay of management continues to be symptomatic control of pain with drugs. Evidence from placebo-controlled studies has shown that opioids, antiepileptic and antidepressant drugs together with capsaicin are effective for alleviating DPN. Tramadol and oxycodone have been shown to be effective in studies of limited duration but their adverse effects, such as constipation and physical dependency, may limit their usefulness as a first-line treatment for DPN. Of the antidepressant drugs, the tricyclic antidepressants have been shown to be effective for alleviating DPN. These medications are widely used but their anticholinergic and sedative properties may not be well tolerated by patients. There is also good evidence that the serotonin-noradrenaline reuptake inhibitor antidepressant drugs venlafaxine and duloxetine are effective for treating DPN. However, venlafaxine may cause cardiac dysrhythmias, and patients using this medication require careful cardiac monitoring. Duloxetine appears to be less cardiotoxic and is licensed in the US and EU for alleviating DPN. The gabapentinoid group of drugs, gabapentin and pregabalin, appear to be the most evidence-based of the antiepileptic drugs for treating DPN. Large placebo-controlled studies have been performed with both of these agents. For many patients, it is still unclear what advantages pregabalin has over gabapentin for DPN. Until better evidence emerges, the potential availability of less expensive generic formulations of gabapentin, together with greater experience with its use, favour gabapentin as the main antiepileptic drug for alleviating DPN. Topiramate, lamotrigine, sodium valproate and oxcarbazepine have been shown to be effective in smaller studies but do not have the same evidence base as the gabapentinoid group of drugs. Of the newer antiepileptic drugs, lacosamide appears to be the most promising for alleviating DPN. Capsaicin has the best evidence base of all the topical agents, but local anaesthetic patches may also have a useful therapeutic role. It is not possible to nominate a single drug as the first-line treatment for DPN and there is evidence that a low-dose combination of two or more drugs rather than a single agent may provide better symptomatic relief with fewer adverse effects. Further studies are necessary to clarify the best combination(s) of treatment for DPN.

Morphine, nortriptyline and their combination vs. placebo in patients with chronic lumbar root pain

Although lumbar radicular pain is the most common chronic neuropathic pain syndrome, there have been few randomized studies of drug treatments. We compared the efficacy of morphine (15-90 mg), nortriptyline (25-100 mg), their combination, and a benztropine "active placebo" (0.25-1 mg) in patients with chronic sciatica. Each period consisted of 5 weeks of dose escalation, 2 weeks of maintenance at the highest tolerated doses, and 2 weeks of dose tapering. The primary outcome was the mean daily leg pain score on a 0-10 scale during the maintenance period. Secondary outcomes included a 6-point ordinal global pain relief scale, the Beck Depression Inventory (BDI), the Oswestry Back Pain Disability Index (ODI) and the SF-36. In the 28 out of 61 patients who completed the study, none of the treatments produced significant reductions in average leg pain or other leg or back pain scores. Pain reduction, relative to placebo treatment was, 14% for nortriptyline (95% CI=[-2%, 30%]), 7% for morphine (95% CI=[-8%, 22%]), and 7% for the combination treatment (95% CI=[-4%, 18%]). Mean doses were: nortriptyline alone, 84+/-24.44 (SD) mg/day; morphine alone, 62+/-29 mg/day; and combination, morphine, 49+/-27 mg/day plus nortriptyline, 55 mg+/-33.18 mg/day. Over half of the study completers reported some adverse effect with morphine, nortriptyline or their combination. Within the limitations of the modest sample size and high dropout rate, these results suggest that nortriptyline, morphine and their combination may have limited effectiveness in the treatment of chronic sciatica.

Sodium channel blockade may contribute to the analgesic efficacy of antidepressants

Sodium channel blockers such as lidocaine, lamotrigine, and carbamazepine can be effective in the treatment of neuropathic pain. Though not approved for neuropathic pain indications, tricyclic antidepressants are often considered first-line treatment for conditions such as post-herpetic neuralgia and diabetic neuropathy. Several tricyclic antidepressants have been shown to block peripheral nerve sodium channels, which may contribute to their antihyperalgesic efficacy. In this study, we compared the sodium channel-blocking potency of a number of antidepressants, including tricyclic antidepressants and selective serotonin reuptake inhibitors. All compounds tested inhibited Na(V)1.7 in a state- and use-dependent manner, with affinities for the inactivated state ranging from 0.24 micromol/L for amitriptyline to 11.6 micromol/L for zimelidine. The tricyclic antidepressants were more potent blockers of Na(V)1.7. Moreover, IC(50)s for block of the inactivated state for amitriptyline, nortriptyline, imipramine, desipramine, and maprotiline were in the range of therapeutic plasma concentrations for both the treatment of depression as well as neuropathic pain. By contrast, fluoxetine, paroxetine, mianserine, and zimelidine had IC(50)s for Na(V)1.7 outside their therapeutic concentration ranges and generally were not efficacious against post-herpetic neuralgia or diabetic neuropathy. These results suggest that block of peripheral nerve sodium channels may contribute to the antihyperalgesic efficacy of certain antidepressants.

PERSPECTIVE

Tricyclic antidepressants are often considered first-line treatment for neuropathic pain. Some tricyclic antidepressants block sodium channels, which may contribute to their antihyperalgesic efficacy. In the current study, we compared the potency of peripheral sodium channel blockade for several tricyclic antidepressants and selective serotonin reuptake inhibitors with their therapeutic efficacy.

[New, relevant and practical aspects of the treatment of neuropathic pain]

In the Spanish population it is difficult to calculate the prevalence of neuropathic pain (NP) although it is estimated that it is present in 40% of the cases of chronic pain. The treatment is not easy and we must choose between the different drugs, the most appropriate taking into account the effectivity in data from clinical trials, releaf of comorbidities associated to NP and less side effects. In this way, the Finnerup NB's work establishes an algorithm of treatment of NP and it is very helpful for clinicians in order to choose the most suitable treatment. In this work, the author recommends antiepileptic drugs, like gabapentin and pregabalin as first choice treatments. Amitriptiline, a tricycle antidepressant and opioids must be used only when there is a lack of response or intolerance.

What is new in neuropathic pain?

INTRODUCTION

Neuropathic pain occurs in 1% of the population and is difficult to manage. Responses to single drugs are limited in benefit. Thirty percent will fail to respond altogether. This is a review of newer drugs and treatment paradigms.

METHODS

A literature review was performed pertinent to new drugs and treatment algorithms in the management of neuropathic pain.

RESULTS

New information on opioids (tramadol and buprenorphine) suggests benefits in the management of neuropathic pain and has increased interest in their use earlier in the course of illness. Newer antidepressants, selective noradrenaline, and serotonin reuptake inhibitors (SNRIs) have evidence for benefit and reduced toxicity without an economic disadvantage compared to tricyclic antidepressants (TCAs). Pregabalin and gabapentin are effective in diabetic neuropathy and postherpetic neuralgia. Treatment paradigms are shifting from sequential single drug trials to multiple drug therapies. Evidence is needed to justify this change in treatment approach.

CONCLUSION

Drug choices are now based not only on efficacy but also toxicity and drug interactions. For this reason, SNRIs and gabapentin/pregabalin have become popular though efficacy is not better than TCAs. Multiple drug therapies becoming an emergent treatment paradigm research in multiple drug therapy are needed.

EFNS guidelines on pharmacological treatment of neuropathic pain

Neuropathic pain treatment remains unsatisfactory despite a substantial increase in the number of trials. This EFNS Task Force aimed at evaluating the existing evidence about the pharmacological treatment of neuropathic pain. Studies were identified using first the Cochrane Database then Medline. Trials were classified according to the aetiological condition. All class I and II controlled trials (according to EFNS classification of evidence) were assessed, but lower-class studies were considered in conditions that had no top level studies. Only treatments feasible in an outpatient setting were evaluated. Effects on pain symptoms/signs, quality of life and comorbidities were particularly searched for. Most of the randomized controlled trials included patients with postherpetic neuralgia (PHN) and painful polyneuropathies (PPN) mainly caused by diabetes. These trials provide level A evidence for the efficacy of tricyclic antidepressants, gabapentin, pregabalin and opioids, with a large number of class I trials, followed by topical lidocaine (in PHN) and the newer antidepressants venlafaxine and duloxetine (in PPN). A small number of controlled trials were performed in central pain, trigeminal neuralgia, other peripheral neuropathic pain states and multiple-aetiology neuropathic pains. The main peripheral pain conditions respond similarly well to tricyclic antidepressants, gabapentin, and pregabalin, but some conditions, such as HIV-associated polyneuropathy, are more refractory. There are too few studies on central pain, combination therapy, and head-to-head comparison. For future trials, we recommend to assess quality of life and pain symptoms or signs with standardized tools.

Oral treatment with alpha-lipoic acid improves symptomatic diabetic polyneuropathy: the SYDNEY 2 trial

OBJECTIVE

The aim of this trial was to evaluate the effects of alpha-lipoic acid (ALA) on positive sensory symptoms and neuropathic deficits in diabetic patients with distal symmetric polyneuropathy (DSP).

RESEARCH DESIGN AND METHODS

In this multicenter, randomized, double-blind, placebo-controlled trial, 181 diabetic patients in Russia and Israel received once-daily oral doses of 600 mg (n = 45) (ALA600), 1,200 mg (n = 47) (ALA1200), and 1,800 mg (ALA1800) of ALA (n = 46) or placebo (n = 43) for 5 weeks after a 1-week placebo run-in period. The primary outcome measure was the change from baseline of the Total Symptom Score (TSS), including stabbing pain, burning pain, paresthesia, and asleep numbness of the feet. Secondary end points included individual symptoms of TSS, Neuropathy Symptoms and Change (NSC) score, Neuropathy Impairment Score (NIS), and patients' global assessment of efficacy.

RESULTS

Mean TSS did not differ significantly at baseline among the treatment groups and on average decreased by 4.9 points (51%) in ALA600, 4.5 (48%) in ALA1200, and 4.7 (52%) in ALA1800 compared with 2.9 points (32%) in the placebo group (all P < 0.05 vs. placebo). The corresponding response rates (>/=50% reduction in TSS) were 62, 50, 56, and 26%, respectively. Significant improvements favoring all three ALA groups were also noted for stabbing and burning pain, the NSC score, and the patients' global assessment of efficacy. The NIS was numerically reduced. Safety analysis showed a dose-dependent increase in nausea, vomiting, and vertigo.

CONCLUSIONS

Oral treatment with ALA for 5 weeks improved neuropathic symptoms and deficits in patients with DSP. An oral dose of 600 mg once daily appears to provide the optimum risk-to-benefit ratio.

painDETECT: a new screening questionnaire to identify neuropathic components in patients with back pain

OBJECTIVE

Nociceptive and neuropathic components both contribute to pain. Since these components require different pain management strategies, correct pain diagnosis before and during treatment is highly desirable. As low back pain (LBP) patients constitute an important subgroup of chronic pain patients, we addressed the following issues: (i) to establish a simple, validated screening tool to detect neuropathic pain (NeP) components in chronic LBP patients, (ii) to determine the prevalence of neuropathic pain components in LBP in a large-scale survey, and (iii) to determine whether LBP patients with an NeP component suffer from worse, or different, co-morbidities.

METHODS

In co-operation with the German Research Network on Neuropathic Pain we developed and validated the painDETECT questionnaire (PD-Q) in a prospective, multicentre study and subsequently applied it to approximately 8000 LBP patients.

RESULTS

The PD-Q is a reliable screening tool with high sensitivity, specificity and positive predictive accuracy; these were 84% in a palm-top computerised version and 85%, 80% and 83%, respectively, in a corresponding pencil-and-paper questionnaire. In an unselected cohort of chronic LBP patients, 37% were found to have predominantly neuropathic pain. Patients with NeP showed higher ratings of pain intensity, with more (and more severe) co-morbidities such as depression, panic/anxiety and sleep disorders. This also affected functionality and use of health-care resources. On the basis of given prevalence of LBP in the general population, we calculated that 14.5% of all female and 11.4% of all male Germans suffer from LBP with a predominant neuropathic pain component.

CONCLUSION

Simple, patient-based, easy-to-use screening questionnaires can determine the prevalence of neuropathic pain components both in individual LBP patients and in heterogeneous cohorts of such patients. Since NeP correlates with more intense pain, more severe co-morbidity and poorer quality of life, accurate diagnosis is a milestone in choosing appropriate therapy.

Recent clinical advances in diabetic polyneuropathy

PURPOSE OF REVIEW

Recent dramatic increases in the incidence and prevalence of diabetes make an understanding of chronic symmetric sensorimotor diabetic polyneuropathy, the most common and problematic of chronic diabetic complications, essential for a wide range of medical practitioners.

RECENT FINDINGS

The demonstration of neuropathic dysfunction in patients with prediabetes or impaired glucose tolerance emphasizes the susceptibility of peripheral nerve fibers, especially small A delta fibers and C fibers, to relatively mild, short-duration hyperglycemia. New testing can reveal peripheral nerve dysfunction prior to clinical neuropathic symptoms and signs. In the absence of effective medications to halt or reverse nerve damage or promote nerve regeneration, early diagnosis of diabetic polyneuropathy, followed by tight glycemic control with diet and exercise, offers the best opportunity to prevent progressive symptoms of sensory loss, pain, autonomic dysfunction, ulcerations, and amputations. Some patients with impaired glucose tolerance have a reversal of neuropathic features with tight glycemic control. Nonpharmacologic therapies for neuropathic pain in diabetic polyneuropathy appear promising.

SUMMARY

Tight glycemic control, especially early in diabetes, is the best approach to minimizing the prevalence and severity of diabetic polyneuropathy and makes research into the deleterious effects of even mild hyperglycemia imperative.

New perspectives on the management of diabetic peripheral neuropathic pain

Peripheral neuropathy affects about 30% of people with diabetes mellitus. Between 16% and 26% of diabetes patients experience chronic pain. This may be referred to as diabetic neuropathic pain (DNP) or diabetic peripheral neuropathic pain (DPNP). Minimum requirements for diagnosis of DPNP should include assessment of pain and symptoms and neurological examination, with the accent on sensory examination. Given that depression and other co-morbidities are commonly associated with this condition, a broad approach to management is essential. Lifestyle intervention and optimisation of glycaemic control are recommended as initial steps in management. An evidence-based treatment algorithm for DPNP has been proposed, recommending initial use of either a tricyclic antidepressant, selective serotonin noradrenaline re-uptake inhibitor or alpha-2-delta agonist, depending on patient co-morbidities and contra-indications. Addition of an opioid agonist may be required in the event of inadequate pain control. Irrespective of which treatment is offered, only about one third of patients are likely to achieve more than 50% pain relief. Further research to improve the diagnosis and management of DPNP is needed.

Neuropathic pain: a practical guide for the clinician

Neuropathic pain, caused by various central and peripheral nerve disorders, is especially problematic because of its severity, chronicity and resistance to simple analgesics. The condition affects 2%-3% of the population, is costly to the health care system and is personally devastating to the people who experience it. The diagnosis of neuropathic pain is based primarily on history (e.g., underlying disorder and distinct pain qualities) and the findings on physical examination (e.g., pattern of sensory disturbance); however, several tests may sometimes be helpful. Important pathophysiologic mechanisms include sodium-and calcium-channel upregulation, spinal hyperexcitability, descending facilitation and aberrant sympathetic-somatic nervous system interactions. Treatments are generally palliative and include conservative nonpharmacologic therapies, drugs and more invasive interventions (e.g., spinal cord stimulation). Individualizing treatment requires consideration of the functional impact of the neuropathic pain (e.g., depression, disability) as well as ongoing evaluation, patient education, reassurance and specialty referral. We propose a primary care algorithm for treatments with the most favourable risk-benefit profile, including topical lidocaine, gabapentin, pregabalin, tricyclic antidepressants, mixed serotonin-norepinephrine reuptake inhibitors, tramadol and opioids. The field of neuropathic pain research and treatment is in the early stages of development, with many unmet goals. In coming years, several advances are expected in the basic and clinical sciences of neuropathic pain, which will provide new and improved therapies for patients who continue to experience this disabling condition.

The role of ketamine in pain management

Ketamine is a dissociative anaesthetic; its mechanism of action is primarily an antagonism of the N-methyl-D-aspartate (NMDA) receptor. The role of ketamine, in particular in lower sub-anaesthetic doses, has recently gained increasing interest in pain management. It has been studied in a considerable number of trials and analysed in meta-analyses and systematic reviews. Based on these data, the primary role of ketamine in such low doses is as an 'anti-hyperalgesic', 'anti-allodynic' or 'tolerance-protective' agent. It therefore has a role in the treatment of opioid resistant or 'pathological' pain (central sensitisation with hyperalgesia or allodynia, opioid induced hyperalgesia, neuropathic pain) rather than as an 'analgesic' in its own right. Low dose ketamine also has 'preventive analgesia' properties. Furthermore, in higher doses it provides effective and safe sedation and analgesia for painful procedures. The place of ketamine in the treatment of chronic pain and the effects of long-term medicinal use remain unclear.

Pharmacological correlation between the formalin test and the neuropathic pain behavior in different species with chronic constriction injury

Research on mechanisms of drug action, and preclinical screening of molecules with a potential activity on neuropathic pain requires extensive animal work. The chronic constriction injury model is one of the best-characterized models of neuropathic pain behavior in rats, but requires extensive time consuming operations and animal handling. The formalin test is easier to perform, and a well validated model. The latter may serve as an effective prescreening test of molecules and may facilitate drug targeting. In the present study the activity of different pharmacological reference compounds was tested in rats and gerbils on the cold plate for animals that had undergone chronic constriction injury and in the second phase of the formalin test. In rats, a comparable outcome in both test conditions was observed for morphine, fentanyl, MK-801 and flunarizine. Clonidine had more activity in the second phase of the formalin test, whereas baclofen, tramadol, amitryptiline, ketamine and topiramate showed more activity in the cold plate. In gerbils, both test conditions yielded comparable results for fentanyl and ketoprofen. Tramadol and CP-96345 tended to have more activity in the second phase of the formalin test, whereas morphine, SR-48968, SR-142801 and R116301 demonstrated more activity in the cold plate test. This study demonstrates a good correlation between the second phase of the formalin test and the cold allodynia in the CCI model for, both for rats and gerbils. Drugs with a proven activity in humans, used as reference compounds, also showed good pharmacological activity in this animal study.

[A case of a second cancer of metachronous multiple primary non-small cell lung cancer successfully treated with TS-1 and CDDP chemotherapy]

The patient was a 66-year-old man who had undergone right upper lobectomy and ND 2a systematic lymph node dissection for lung cancer (M/D adenocarcinoma, p-stage IB) in March of 1999 . On November 2003, postoperative routine chest computed tomography(CT) demonstrated a mass in left S6, and pathological diagnosis revealed P/D squamous cell carcinoma (cT1N2M0, stage IIIA) by CT-guided needle biopsy and mediastinoscopy. At first, we tried two courses of a combination chemotherapy consisting of carboplatin (CBDCA) and paclitaxel every 3 weeks. After 2 courses, the regimen was stopped because of grade 3 arthritis. Then, two courses of CBDCA and gemcitabine were performed. The evaluation of the response was SD by the guidelines of Response Evaluation Criteria in Solid Tumor Groups. Next, gefitinib was orally administered for 6 months but the tumor and mediastinal lymph nodes were growing. In January 2005, oral administration of TS-1 (60 mg/1, 2 courses, 75 mg/3-6 courses) was begun twice a day for 21 consecutive days while cisplatin (60 mg/m(2)) was administered intravenously on day 8. The response was PR (the tumor decreased by 46%), no serious adverse effect was observed, and the patient maintained good quality of life throughout the chemotherapy. This case suggests that TS-1+CDDP chemotherapy may be an effective treatment in patients with advanced lung cancer even after many protocols of chemotherapy.

Trends in utilization of antiepileptic drugs in Denmark

OBJECTIVES

To describe utilization of antiepileptic drugs (AEDs) in Denmark during 1993-2002, with special emphasis on oxcarbazepine, and to assess probable indications for AED use.

MATERIALS AND METHODS

We retrieved prescription data from Odense University Pharmacoepidemiological Database, in Funen County, Denmark (population in 2002: 472,869). Within each calendar year we estimated period prevalence, incidence rate and monotherapy rate. Based on co-medication we defined 'epilepsy' when only AEDs were prescribed, 'pain' with co-prescription of opioids, and 'mood disorder' with co-prescription of antipsychotics or antidepressants.

RESULTS

We identified 15,604 AED users. The prevalence of using AED increased from 9.3 (95% CI, 9-9.5) to 12.1 (11.8-12.4)/1000 persons. The incidence rate increased from 1.4 (1.3-1.6) to 1.7 (1.6-1.9)/1000 personyears. The monotherapy rate was 79-82%. AED use for 'epilepsy' declined by 19.7%, whereas the proportion of 'pain' and 'mood disorder' treatment increased by 11.2% and 8.4% respectively.

CONCLUSIONS

Antiepileptic drug utilization increased during the study period, the increase probably caused by expanding use in areas other than epilepsy.

Perioperative management of chronic pain patients with opioid dependency

PURPOSE OF REVIEW

In this article, we discuss the perioperative anesthesia and pain management of patients with chronic pain receiving chronic opioid administration. In our practice we may expect to be confronted with opioid-dependent patients in routine anesthesia practice and should acquire specific knowledge and skills to effectively manage the perioperative and acute pain management issues that arise.

RECENT FINDINGS

The number of patients treated chronically with opioids has increased steadily over the past decade; currently about 10% of all chronic-pain patients are treated with opioids. As these patients are no longer confined to terminally ill cancer patients, growing numbers of these patients are facing surgical interventions.

SUMMARY

In our clinical practice, we should employ multimodal pain management therapy by using an around-the-clock regimen of nonsteroidal anti-inflammatory drugs, cyclooxygenase-2 inhibitors, acetaminophen, and regional blockade. Dosing regimens should be individualized to optimize efficacy while minimizing the risk of adverse events.

Adjunctive pharmacological management of persistent, nonmalignant pain in older individuals

Chronic or persistent pain is a common comorbidity of aging, primarily due to the relatively high frequency of pain-associated disorders in this population (e.g., inflammatory and noninflammatory musculoskeletal disease, zoster infection, diabetes, stroke, and peripheral and central neurological diseases). Acetaminophen, nonsteroidal anti-inflammatory drugs and opioids are important long-term analgesics in this age group. However, adjunctive agents are also important in the management of persistent pain in the elderly, especially neuropathic pain. Oral antiepileptic drugs, mexiletine, baclofen, tricyclic antidepressants, selective serotonin–norepinephrine dual reuptake inhibitors and intranasal/injectable calcitonin are the subjects of this review of the management of persistent, nonmalignant pain in the elderly. While some of these agents are considered narrow-spectrum analgesics (e.g., baclofen in trigeminal neuralgia and calcitonin in bone pain), most are broad-spectrum analgesics, useful in neuropathic pain syndromes of multiple etiologies. Within the antiepileptic drug class, gabapentin and carbamazepine can be considered first-line agents, followed by lamotrigine and pregabalin as second-line agents, and the other most recently approved drugs as third-line or ‘salvage’ agents. The tricyclic antidepressants have numerous precautions/contraindications and tolerability issues in this population, thus reducing their utility. Duloxetine and venlafaxine are the only useful analgesics among the modern antidepressants. Challenges for the future include not only the search for more effective and less toxic adjunctive analgesics for the elderly, but also translating our knowledge of current and future analgesics into effective therapies in the ‘real world’ community and institutional settings where elderly people live. There is no justification in our society today for anyone to live with untreated or undertreated persistent pain.

Mechanisms of Disease: mechanism-based classification of neuropathic pain—a critical analysis

Classification of neuropathic pain according to etiology or localization has clear limitations. The discovery of specific molecular and cellular events following experimental nerve injury has raised the possibility of classifying neuropathic pain on the basis of the underlying neurobiological mechanisms. Application of this approach in the clinic is problematic, however, owing to a lack of precise tools to assess symptoms and signs, and difficulties in correlating symptoms and signs with mechanisms. Development and validation of diagnostic methods to identify mechanisms, together with pharmacological agents that specifically target these mechanisms, seems to be the most logical and rational way of improving neuropathic pain treatment.

Carbamazepine for acute and chronic pain

BACKGROUND

Anticonvulsant drugs have been used in the management of pain since the 1960s. The clinical impression is that they are useful for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of the anticonvulsant medicine carbamazepine for pain management in clinical practice and to identify a clinical research agenda. Migraine and headache studies are not included in this review.

SEARCH STRATEGY

Randomised trials (RCTs) of anticonvulsants in acute, chronic or cancer pain were identified by MEDLINE (1966-2004), EMBASE (1994-2004), SIGLE (1980-2004) and the Cochrane Controlled Trials Register (CENTRAL/CCTR) (Cochrane Library Issue 3, 2003). In addition, 41 medical journals were hand searched for a previous version of this review. Additional reports were identified from the reference list of the retrieved papers, and by contacting investigators. Date of most recent search: November 2004.

SELECTION CRITERIA

Randomised trials reporting the analgesic effects of carbamazepine in patients, with subjective pain assessment as either the primary or a secondary outcome.

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent reviewers, and trials were quality scored. Numbers-needed-to-treat (NNTs) were calculated from dichotomous data for effectiveness, adverse effects and drug-related study withdrawal, for individual studies and for pooled data.

MAIN RESULTS

Twelve studies were included (404 participants). Four studies included trigeminal neuralgia patients. Two studies which provided evaluable data yielded an NNT for effectiveness of 1.8 (95%CI 1.4-2.8). For diabetic neuropathy there was insufficient data for an NNT to be calculated.Numbers-needed-to-harm (NNHs) were calculated where possible by combining studies for each drug entity irrespective of the condition treated. The results were, for minor harm, carbamazepine 3.7 (CI 2.4-7.8), NNHs for major harm were not statistically significant for carbamazepine compared with placebo. There is no evidence that carbamazepine is effective for acute pain.

AUTHORS' CONCLUSIONS

There is evidence to show that carbamazepine is effective but trials are small.