Duloxetine for treating painful neuropathy or chronic pain

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Low back pain: pharmacologic management

Adequate treatment of low back pain is essential, but has been challenging for many primary care physicians. Most patients with low back pain can be treated in the primary care environment, provided the physician has enough knowledge of the medications used to treat low back pain. The main treatment goal for acute low back pain is to control the pain and maintain function. For patients with chronic back pain, the goal is continual pain management and prevention of future exacerbations. This article reviews current pharmacological options for the treatment of low back pain, and possible future innovations.

Diabetic neuropathies: diagnosis and management

INTRODUCTION

Changes in human behaviour and lifestyle over the last century have resulted in a dramatic increase in the incidence of diabetes worldwide. Neuropathy is a common and costly complication of both type 1 and type 2 diabetes. The prevalence of neuropathy is estimated to be about 8% in newly diagnosed patients and greater than 50% in patients with long-standing disease. There are two main types of diabetic neuropathies, named as sensorimotor and autonomic neuropathies. Sensorimotor neuropathy is marked by pain, paraesthesia and sensory loss, and autonomic neuropathy may contribute to myocardial infarction, malignant arrhythmia and sudden death.

METHODS

In this article we reviewed the pathogenesis, clinical manifestations diagnosis and treatment of diabetic neuropathies.

CONCLUSION

Sensorimotor and autonomic neuropathies (cardiovascular, gastrointestinal and genitourinary autonomic neuropathies) are common in diabetic patients. Apart from strict glycaemic control, no further therapeutic approach exists in the prevention of this phenomenon. Intensive diabetes therapy, intensive multifactorial cardiovascular risk reduction and lifestyle intervention are recommended in patients with cardiovascular autonomic neuropathy. Gastroparesis is the most debilitating complication of gastrointestinal autonomic neuropathy and genitourinary autonomic neuropathy can cause sexual dysfunction and neurogenic bladder; these conditions are hard to manage. The symptomatic treatment of sensory symptoms includes tricyclic antidepressants, serotonin and norepinephrine reuptake inhibitors, gabapentin, pregabalin and opioids. Other treatment strategies are not so effective.

Early vs. conventional switching of antidepressants in patients with MDD and moderate to severe pain: a double-blind randomized study

BACKGROUND

Concomitant painful physical symptoms in depressive patients frequently impair functioning and failure to treat these symptoms may adversely impact treatment outcomes of depression. Early vs. conventional switch of antidepressants were compared in patients with major depressive disorder (MDD) and moderate to severe pain.

METHOD

Pre-specified subgroup analysis of a 16-week, randomized, double-blind clinical study on MDD patients with >30 mm overall pain visual analog scale (VAS). Patients not achieving 30% reduction Hamilton Depression Rating Scale (HAM-D) after 4 weeks escitalopram (10 mg/day) were randomized to duloxetine 60-120 mg/day (early switch) or continued on escitalopram (conventional switch) with non-responders at week 8 switching to duloxetine. Endpoints were time to confirmed response and remission, VAS pain severity, and Sheehan disability scale (SDS). Switch strategies were compared using Kaplan-Meier, logistic regression, and repeated measures analyses.

RESULTS

No differences between early and conventional switching were found in time to confirmed response after randomization (3.9 vs. 4.1 weeks, p=0.511) or remission (6.0 vs. 8.0 weeks, p=0.238). Significantly lower VAS mean pain levels at for overall pain, headache, back pain, shoulder pain, interference with daily activities, and time being awake in pain were found for patients in the early switching group. Time to achieving normal functioning (SDS total score <6) was shorter in the early switching group (p=0.042). Safety results were comparable between switch strategies.

CONCLUSIONS

In MDD patients with moderate to severe painful physical symptoms not improving after 4 weeks of treatment with escitalopram, an earlier switch to duloxetine may lead to better pain and functional outcomes.

Amitriptyline for neuropathic pain and fibromyalgia in adults

BACKGROUND

Amitriptyline is a tricyclic antidepressant that is widely used to treat chronic neuropathic pain (pain due to nerve damage) and fibromyalgia, and is recommended in many guidelines. These types of pain can be treated with antidepressant drugs in doses below those at which the drugs act as antidepressants.

OBJECTIVES

To assess the analgesic efficacy of amitriptyline for chronic neuropathic pain and fibromyalgia.To assess the adverse events associated with the clinical use of amitriptyline for chronic neuropathic pain and fibromyalgia.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and EMBASE to September 2012, together with reference lists of retrieved papers, previous systematic reviews, and other reviews; we also used our own handsearched database for older studies.

SELECTION CRITERIA

We included randomised, double-blind studies of at least four weeks' duration comparing amitriptyline with placebo or another active treatment in chronic neuropathic pain or fibromyalgia.

DATA COLLECTION AND ANALYSIS

We extracted efficacy and adverse event data, and two study authors examined issues of study quality independently. We performed analysis using two tiers of evidence. The first tier used data meeting current best standards, where studies reported the outcome of at least 50% pain intensity reduction over baseline (or its equivalent), without the use of last observation carried forward (LOCF) or other imputation method for dropouts, reported an intention-to-treat (ITT) analysis, lasted 8 to 12 weeks or longer, had a parallel-group design, and where there were at least 200 participants in the comparison. The second tier used data that failed to meet this standard and were therefore subject to potential bias.

MAIN RESULTS

Twenty-one studies (1437 participants) were included; they individually involved between 15 and 235 participants, only four involved over 100 participants, and the median study size was 44 participants. The median duration was six weeks. Ten studies had a cross-over design. Doses of amitriptyline were generally between 25 mg and 125 mg, and dose escalation was common.There was no top-tier evidence for amitriptyline in treating neuropathic pain or fibromyalgia.Second-tier evidence indicated no evidence of effect in cancer-related neuropathic pain or HIV-related neuropathic pain, but some evidence of effect in painful diabetic neuropathy (PDN), mixed neuropathic pain, and fibromyalgia. Combining the classic neuropathic pain conditions of PDN, postherpetic neuralgia (PHN) and post-stroke pain with fibromyalgia for second-tier evidence, in eight studies and 687 participants, there was a statistically significant benefit (risk ratio (RR) 2.3, 95% confidence interval (CI) 1.8 to 3.1) with a number needed to treat (NNT) of 4.6 (3.6 to 6.6). The analysis showed that even using this potentially biased data, only about 38% of participants benefited with amitriptyline and 16% with placebo; most participants did not get adequate pain relief. Potential benefits of amitriptyline were supported by a lower rate of lack of efficacy withdrawals; 8/153 (5%) withdrew because of lack of efficacy with amitriptyline and 14/119 (12%) with placebo.More participants experienced at least one adverse event; 64% of participants taking amitriptyline and 40% taking placebo. The RR was 1.5 (95% CI 1.4 to 1.7) and the number needed to treat to harm was 4.1 (95% CI 3.2 to 5.7). Adverse event and all-cause withdrawals were not different.

AUTHORS' CONCLUSIONS

Amitriptyline has been a first-line treatment for neuropathic pain for many years. The fact that there is no supportive unbiased evidence for a beneficial effect is disappointing, but has to be balanced against decades of successful treatment in many patients with neuropathic pain or fibromyalgia. There is no good evidence of a lack of effect; rather our concern should be of overestimation of treatment effect. Amitriptyline should continue to be used as part of the treatment of neuropathic pain or fibromyalgia, but only a minority of patients will achieve satisfactory pain relief. Limited information suggests that failure with one antidepressant does not mean failure with all.It is unlikely that any large randomised trials of amitriptyline will be conducted in specific neuropathic pain conditions or in fibromyalgia to prove efficacy.

Opioids for the treatment of chronic noncancer pain

Increasingly, opioids are used to treat chronic noncancer pain. While opioids are well recognized for their effectiveness in treating acute pain, the evidence supporting the benefits for the treatment of chronic pain is less well established. Improvement of both pain and function should be considered goals of therapy. Patients with chronic pain have a higher incidence of preexisting psychological disorders. Adverse effects of opioid therapy include dependence, overdose, and withdrawal. Risk factors for poor outcomes with opioid therapy are identified, and include preexisting mental illness and dose prescribed. Recommended strategies to more safely use opioids are discussed, including tools for identifying high-risk patients. The evidence supporting the use of treatment agreements and urine drug testing to reduce the effects of adverse outcomes is limited.

Management of radicular pain in rheumatic disease: insight for the physician

Rheumatologists are still relatively unaware of the causes, presentation, diagnosis and management of radicular pain. This is against a background of increasing evidence of the presence and importance of radicular problems in patients with rheumatological disorders. When they coexist in patients, differentiating between nociceptive and neuropathic pain is clinically important because these components require different pain management strategies. Consequently, it is essential that rheumatologists become skilled in identifying as well as managing both forms of pain. This review will serve to further increase awareness among rheumatologists of this important issue as well as discuss the practical aspects of managing these conditions. The evaluation of patients requires very careful history taking and full thorough neurological examination. Diagnostic testing is suggested mainly to confirm the diagnosis and aetiology in patients with persistent symptoms despite conservative treatment. Neuroimaging is recommended for patients with acute radicular pain with progressive neurological deficits or those with high suspicion of neoplasm or epidural abscess. If neuroimaging does not confirm diagnosis, electrophysiology studies may be helpful. The management of this condition is multifaceted and involves physicians and allied healthcare professionals as well as the patients who should be encouraged to participate in self-management programmes. Nociceptive and neuropathic pain often coexists in patients with rheumatic disease. There are challenges to making the diagnosis of radicular pain in these patients. The diagnosis is primarily clinical but pathophysiological issues, diversity in symptoms, the multiple mechanisms of action and difficulties in communication between patients and their doctors as well as variable response to therapy pose challenges to the effective management of these patients. Despite these difficulties and challenges, it is essential that rheumatologists familiarize themselves with the management of radicular pain in rheumatic diseases. The evaluation of patients requires very careful history taking, aided by the use of an appropriate screening tool and full, thorough neurological examination. In addition, investigations such as the use of imaging or electrophysiology studies when required may help to differentiate between the pain phenotypes.

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.

Pharmacological management of persistent pain in older persons

Drugs without a strong evidence base and outside of recommendations are too often prescribed for older adults. Established guidelines such as Beers criteria have identified both specific medications and certain drug classes as inappropriate for older adults, primarily due to adverse effects. Age-related physiological changes in distribution, metabolism, and elimination often alter the effects of pharmacotherapies in older adults. When designing a therapeutic program, all elements contributing to the pathophysiology of painful conditions should be considered, as well as the mechanisms of action of analgesic drug classes. Both appropriate and inappropriate medications for older adults are detailed herein, as well as their contraindications and potential drug-drug or drug-disease interactions. The number needed to treat (NNT) can be useful in considering efficacy, while the safety of a pharmacotherapy is indicated by the calculated number needed to harm (NNH). The NNT is a measure describing the number of patients who require treatment for every 1 who reaches the therapeutic goal, and the NNH describes the number of participants who manifest side effects; these can further be segregated into numbers who withdraw from studies due to intolerable side effects. These parameters, along with a patient's comorbidities and concomitant medications, should be considered when selecting an analgesic and dose regimen. In addition, practitioners should avoid prescribing multiple-drug therapies that have overlapping pharmacodynamics or that may have an adverse pharmacokinetic interaction.

Pharmacodynamic analysis of the analgesic effect of capsaicin 8% patch (Qutenza™) in diabetic neuropathic pain patients: detection of distinct response groups

Treatment of chronic pain is associated with high variability in the response to pharmacological interventions. A mathematical pharmacodynamic model was developed to quantify the magnitude and onset/offset times of effect of a single capsaicin 8% patch application in the treatment of painful diabetic peripheral neuropathy in 91 patients. In addition, a mixture model was applied to objectively match patterns in pain-associated behavior. The model identified four distinct subgroups that responded differently to treatment: 3.3% of patients (subgroup 1) showed worsening of pain; 31% (subgroup 2) showed no change; 32% (subgroup 3) showed a quick reduction in pain that reached a nadir in week 3, followed by a slow return towards baseline (16% ± 6% pain reduction in week 12); 34% (subgroup 4) showed a quick reduction in pain that persisted (70% ± 5% reduction in week 12). The estimate of the response-onset rate constant, obtained for subgroups 1, 3, and 4, was 0.76 ± 0.12 week⁻¹ (median ± SE), indicating that every 0.91 weeks the pain score reduces or increases by 50% relative to the score of the previous week (= t½). The response-offset rate constant could be determined for subgroup 3 only and was 0.09 ± 0.04 week⁻¹ (t½ 7.8 weeks). The analysis allowed separation of a heterogeneous neuropathic pain population into four homogenous subgroups with distinct behaviors in response to treatment with capsaicin. It is argued that this model-based approach may have added value in analyzing longitudinal chronic pain data and allows optimization of treatment algorithms for patients suffering from chronic pain conditions.

Gynecologic management of neuropathic pain

Obstetrician/gynecologists often are the initial management clinicians for pelvic neuropathic pain. Although treatment may require comprehensive team management and consultation with other specialists, there are a few critical and basic steps that can be performed during an office visit that offer the opportunity to improve quality of life significantly in this patient population. A key first step is a thorough clinical examination to map the pain site physically and to identify potentially involved nerves. Only limited evidence exists about how best to manage neuropathic pain; generally, a combination of surgical, manipulative, or pharmacologic methods should be considered. Experimental methods to characterize more precisely the nature of the nerve dysfunction exist to diagnose and treat neuropathic pain; however, additional scientific evidence is needed to recommend these options unanimously. In the meantime, an approach that was adopted from guidelines of the International Association for the Study of Pain has been tailored for gynecologic pain.

Valproic acid and sodium valproate for neuropathic pain and fibromyalgia in adults

BACKGROUND

Valproic acid and its sodium salt (sodium valproate) are antiepileptic drugs that are sometimes used to treat chronic neuropathic pain and fibromyalgia, although they are not licensed for this use.

OBJECTIVES

To evaluate the analgesic efficacy and adverse effects of valproic acid and sodium valproate in the management of chronic neuropathic pain and fibromyalgia.

SEARCH STRATEGY

We identified randomised controlled trials (RCTs) of valproic acid and sodium valproate in acute, and chronic pain by searching MEDLINE, EMBASE and Cochrane CENTRAL to June 2011, together with reference lists of retrieved papers and reviews.

SELECTION CRITERIA

RCTs that were double blind and of eight-weeks duration or longer, reporting on analgesic effects and adverse events with valproic acid and sodium valproate in the treatment of chronic neuropathic pain and fibromyalgia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted results and scored for quality. We extracted efficacy and adverse event data, and examined issues of study quality.

MAIN RESULTS

We included three studies, two in diabetic neuropathy (42 participants treated with valproate, 42 with placebo), and one in post-herpetic neuralgia (23 treated with divalproex sodium, 22 with placebo). Study duration was eight or 12 weeks. No studies were found in fibromyalgia.Only one study reported one of our primary outcomes (≥ 50% pain relief), while all three reported group means for pain reduction from baseline to endpoint. In all three studies; efficacy results were given only for participants who completed the study. One study in diabetic neuropathy and the study in post-herpetic neuralgia reported significant differences between active and placebo groups, but there were insufficient data for reliable pooled analysis.More adverse events were reported with active treatment than placebo, and included nausea, drowsiness and abnormal liver function tests. One participant taking sodium valproate withdrew due to serious derangement of liver enzymes.

AUTHORS' CONCLUSIONS

These three studies no more than hint that sodium valproate may reduce pain in diabetic neuropathy, and divalproex sodium in post-herpetic neuralgia, but the use of 'completer' analysis may overestimate efficacy, and there were too few data for pooled analysis of efficacy or harm, or to have confidence in the results of the individual studies. There is insufficient evidence to support the use of valproic acid or sodium valproate as a first-line treatment for neuropathic pain. There is more robust evidence of greater efficacy for a small number of other drugs.

Diabetic neuropathy: cellular mechanisms as therapeutic targets

In patients with diabetes, nerve injury is a common complication that leads to chronic pain, numbness and substantial loss of quality of life. Good glycemic control can decrease the incidence of diabetic neuropathy, but more than half of all patients with diabetes still develop this complication. There is no approved treatment to prevent or halt diabetic neuropathy, and only symptomatic pain therapies, with variable efficacy, are available. New insights into the mechanisms leading to the development of diabetic neuropathy continue to point to systemic and cellular imbalances in metabolites of glucose and lipids. In the PNS, sensory neurons, Schwann cells and the microvascular endothelium are vulnerable to oxidative and inflammatory stress in the presence of these altered metabolic substrates. This Review discusses the emerging cellular mechanisms that are activated in the diabetic milieu of hyperglycemia, dyslipidemia and impaired insulin signaling. We highlight the pathways to cellular injury, thereby identifying promising therapeutic targets, including mitochondrial function and inflammation.

A spinal mechanism of action for duloxetine in a rat model of painful diabetic neuropathy

BACKGROUND AND PURPOSE

This study was designed to clarify mechanisms responsible for the anti-allodynic effects of duloxetine in diabetes.

EXPERIMENTAL APPROACH

The streptozotocin-induced diabetic rat model was used to compare the efficacy of duloxetine, 5-HT, the 5-HT(2A) receptor agonist [1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI)] and two antagonists (ketanserin and pruvanserin) on tactile allodynia.

KEY RESULTS

Systemic or intrathecal injection of duloxetine alleviated tactile allodynia in diabetic rats. The effect of systemic duloxetine was reduced by intrathecal administration of ketanserin or pruvanserin, indicating participation of spinal 5-HT(2A) receptors in the mechanism of action of duloxetine. In contrast to spinal delivery, systemic and local peripheral injections of ketanserin or pruvanserin alleviated tactile allodynia in diabetic rats. This effect was reversed immediately after systemic or local DOI injection.

CONCLUSIONS AND IMPLICATIONS

These results support the involvement of spinal 5-HT(2A) receptors in the ability of duloxetine to ameliorate painful diabetic neuropathy. Our data also suggest that the role of 5-HT(2A) receptors depends on the level of the neuraxis at which activation takes place, with peripheral activation contributing to tactile allodynia in diabetic rats, whereas spinal activation of this receptor alleviates tactile allodynia. The development of selective peripheral 5-HT(2A) receptor antagonists may offer a novel approach for the treatment of diabetic neuropathic pain.

Assessment of the quality of postherpetic neuralgia treatment information on the Internet

The objective of this study was to assess the quality of websites presenting treatment information for postherpetic neuralgia. The term "postherpetic neuralgia treatment" was searched using the Google and Yahoo search engines. Fifty websites from each were evaluated using the Journal of the American Medical Association (JAMA) benchmarks, the Health on the Net (HON) seal, and the DISCERN instrument. The treatments suggested on each website were compared with 3 recognized first-line treatment options (antidepressants, anticonvulsants, and topical lidocaine). Less than half of the included websites fulfilled all JAMA benchmark requirements. Less than one-third of the websites displayed the HON seal. The DISCERN instrument evaluation revealed that most websites were of moderate quality. Commercial websites tended to be inferior in comparison to noncommercial websites. Most websites recommended at least 2 of the 3 recommended treatments as well as several second- and third-line treatments. One-third to one-half of websites recommended a nonbeneficial treatment. In conclusion, many different postherpetic neuralgia treatments are found on the Internet and patients may be left separating recommended treatments from nonrecommended treatments without help from their healthcare providers.

PERSPECTIVE

This study examined the quality of websites related to postherpetic neuralgia treatment. The results demonstrated that most websites offering advice on postherpetic neuralgia treatment are of only moderate quality and often offer treatment suggestions that are nonbeneficial. Patients and providers must use caution when taking advice from these sites.

Duloxetine in the management of diabetic peripheral neuropathic pain

Diabetic neuropathy affects up to 70% of diabetics, and diabetic peripheral neuropathic pain (DPNP) is the most common and debilitating of the diabetic neuropathies. DPNP significantly reduces quality of life and increases management costs in affected patients. Despite the impact of DPNP, management is poor with one-quarter of patients receiving no treatment and many treated with medications having little or no efficacy in managing DPNP. Duloxetine is one of two drugs approved by the United States Food and Drug Administration for DPNP management. Duloxetine is a serotonin and norepinephrine reuptake inhibitor (SNRI) proven safe, effective, and cost-saving in reducing DPNP symptoms at a dose of 60 mg/day. Duloxetine doses greater than 60 mg/day for DPNP management are not recommended since they are no more efficacious and associated with more side effects; addition of pregabalin or gabapentin for these patients may be beneficial. Side effects of duloxetine are generally mild and typical for the SNRI class including nausea, dizziness, somnolence, fatigue, sweating, dry mouth, constipation, and diarrhea. Given its other indications, duloxetine is a particularly good choice for DPNP treatment in patients with coexisting depression, anxiety, fibromyalgia, or chronic musculoskeletal pain. Duloxetine treatment had no clinically significant effect on glycemic control and did not increase the risk of cardiovascular events in diabetes patients. However, duloxetine use should be avoided in patients with hepatic disease or severe renal impairment. Given its safety, efficacy, and tolerability, duloxetine is an excellent choice for DPNP treatment in many patients.

A comparative evaluation of amitriptyline and duloxetine in painful diabetic neuropathy: a randomized, double-blind, cross-over clinical trial

OBJECTIVE

To compare the efficacy and safety of duloxetine and amitriptyline in painful diabetic neuropathy (PDN).

RESEARCH DESIGN AND METHODS

In this randomized, double-blind, cross-over, active-control trial, 58 patients received amitriptyline and duloxetine orally once daily at bedtime, each for 6 weeks with optional dose uptitration fortnightly. Single-blinded placebo washout was given for 2 weeks between the two treatments and a single-blinded placebo run-out phase of 4 weeks was given at the end of the treatment period. Pain relief was measured by the patient's global assessment of efficacy, using a visual analog scale (0-100) as a primary end point, and overall improvement and adverse events were assessed as secondary outcome measures. Median pain score reductions of >50%, 25-50%, and <25% were considered good, moderate, and mild responses, respectively.

RESULTS

There was a significant improvement in pain with both treatments compared with their baseline values (P < 0.001 for both). Good, moderate, and mild pain relief was achieved in 55, 24, and 15% of patients, respectively, on amitriptyline and 59, 21, and 9% of patients, respectively, on duloxetine. There were no significant differences in various other outcome measures between the groups. Of the reported adverse events, dry mouth was significantly more common with amitriptyline than duloxetine (55 vs. 24%; P < 0.01). Although, numerically, more patients preferred duloxetine, overall this was not statistically significant (48 vs. 36%; P = 0.18).

CONCLUSIONS

Both duloxetine and amitriptyline demonstrated similar efficacy in PDN. A large, multicentric clinical trial in other populations could possibly demonstrate the superiority of either drug.

Gabapentin for chronic neuropathic pain and fibromyalgia in adults

BACKGROUND

This review updates parts of two earlier Cochrane reviews investigating effects of gabapentin in chronic neuropathic pain (pain due to nerve damage). Antiepileptic drugs are used to manage pain, predominantly for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of gabapentin for chronic neuropathic pain management.

SEARCH STRATEGY

We identified randomised trials of gabapentin in acute, chronic or cancer pain from MEDLINE, EMBASE, and CENTRAL. We obtained clinical trial reports and synopses of published and unpublished studies from Internet sources. The date of the most recent search was January 2011.

SELECTION CRITERIA

Randomised, double-blind studies reporting the analgesic and adverse effects of gabapentin in neuropathic pain with assessment of pain intensity and/or pain relief, using validated scales. Participants were adults aged 18 and over.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data. We calculated numbers needed to treat to benefit (NNTs), concentrating on IMMPACT (Initiative on Methods, Measurement and Pain Assessment in Clinical Trials) definitions of at least moderate and substantial benefit, and to harm (NNH) for adverse effects and withdrawal. Meta-analysis was undertaken using a fixed-effect model.

MAIN RESULTS

Twenty-nine studies (3571 participants), studied gabapentin at daily doses of 1200 mg or more in 12 chronic pain conditions; 78% of participants were in studies of postherpetic neuralgia, painful diabetic neuropathy or mixed neuropathic pain. Using the IMMPACT definition of at least moderate benefit, gabapentin was superior to placebo in 14 studies with 2831 participants, 43% improving with gabapentin and 26% with placebo; the NNT was 5.8 (4.8 to 7.2). Using the IMMPACT definition of substantial benefit, gabapentin was superior to placebo in 13 studies with 2627 participants, 31% improving with gabapentin and 17% with placebo; the NNT was 6.8 (5.6 to 8.7). These estimates of efficacy are more conservative than those reported in a previous review. Data from few studies and participants were available for other painful conditions.Adverse events occurred significantly more often with gabapentin. Persons taking gabapentin can expect to have at least one adverse event (66%), withdraw because of an adverse event (12%), suffer dizziness (21%), somnolence (16%), peripheral oedema (8%), and gait disturbance (9%). Serious adverse events (4%) were no more common than with placebo.There were insufficient data for comparisons with other active treatments.

AUTHORS' CONCLUSIONS

Gabapentin provides pain relief of a high level in about a third of people who take if for painful neuropathic pain. Adverse events are frequent, but mostly tolerable. More conservative estimates of efficacy resulted from using better definitions of efficacy outcome at higher, clinically important, levels, combined with a considerable increase in the numbers of studies and participants available for analysis.

Lamotrigine for acute and chronic pain

BACKGROUND

This is an update of the original Cochrane review published in Issue 2, 2007. Some antiepileptic medicines have a place in the treatment of neuropathic pain (pain due to nerve damage). This updated review adds five new additional studies looking at evidence for Lamotrigine as an effective treatment for acute and chronic pain.

OBJECTIVES

To assess analgesic efficacy and adverse effects of the antiepileptic drug lamotrigine in acute and chronic pain.

SEARCH STRATEGY

Randomised controlled trials (RCTs) of lamotrigine in acute, and chronic pain (including cancer pain) were identified from MEDLINE, EMBASE and CENTRAL up to January 2011. Additional studies were sought from the reference list of the retrieved papers.

SELECTION CRITERIA

RCTs investigating the use of lamotrigine (any dose, by any route, and for any study duration) for the treatment of acute or chronic pain. Assessment of pain intensity or pain relief, or both, using validated scales. Participants were adults aged 18 and over. Only full journal publication articles were included.

DATA COLLECTION AND ANALYSIS

Dichotomous data (ideally for the outcome of at least 50% pain relief) were used to calculate relative risk with 95% confidence intervals. Meta-analysis was undertaken using a fixed-effect model. Numbers needed to treat to benefit (NNTs) were calculated as the reciprocal of the absolute risk reduction. For unwanted effects, the NNT becomes the number needed to harm (NNH) and was calculated.

MAIN RESULTS

Twelve included studies in 11 publications (1511 participants), all with chronic neuropathic pain: central post stroke pain (1), chemotherapy induced neuropathic pain (1), diabetic neuropathy (4), HIV related neuropathy (2), mixed neuropathic pain (2), spinal cord injury related pain (1), and trigeminal neuralgia (1); none investigated lamotrigine in acute pain. The update had five additional studies (1111 additional participants). Participants were aged between 26 and 77 years. Study duration was 2 weeks in one study and at least 6 weeks in the remainder; eight were of eight week duration or longer. There is no convincing evidence that lamotrigine is effective in treating acute or chronic pain at doses of about 200-400 mg daily. Almost 10% of participants taking lamotrigine reported a skin rash.

AUTHORS' CONCLUSIONS

The additional studies tripled participant numbers providing data for analysis, and new, more stringent criteria for outcomes and analysis were used; conclusions about lamotrigine's lack of efficacy in chronic pain did not change. Given availability of more effective treatments including antiepileptics and antidepressant medicines, lamotrigine does not have a significant place in therapy based on available evidence.

Duloxetine in the treatment of chronic pain due to fibromyalgia and diabetic neuropathy

Duloxetine is a serotonin-norepinephrine reuptake inhibitor approved by the US Food and Drug Administration for the treatment of fibromyalgia and painful diabetic neuropathy at doses of 60 mg daily. Duloxetine has been shown to significantly improve the symptoms of chronic pain associated with these disorders, as measured by the Fibromyalgia Impact Questionnaire, Brief Pain Inventory scores, the Clinical Global Impressions Scale, and other various outcome measures in several placebo-controlled, randomized, double-blind, multicenter studies. Symptom improvement generally began within the first few weeks, and continued for the duration of the study. In addition, the efficacy of duloxetine was found to be due to direct effects on pain symptoms rather than secondary to improvements in depression or anxiety. Adverse events including nausea, constipation, dry mouth, and insomnia, were mild and transient and occurred at relatively low rates. In conclusion, duloxetine, a selective inhibitor for the serotonin and norepinephrine transporters, is efficacious in the treatment of chronic pain associated with fibromyalgia or diabetic neuropathy, and has a predictable tolerability profile, with adverse events generally being mild to moderate.

Diabetic neuropathies: update on definitions, diagnostic criteria, estimation of severity, and treatments

Preceding the joint meeting of the 19th annual Diabetic Neuropathy Study Group of the European Association for the Study of Diabetes (NEURODIAB) and the 8th International Symposium on Diabetic Neuropathy in Toronto, Canada, 13-18 October 2009, expert panels were convened to provide updates on classification, definitions, diagnostic criteria, and treatments of diabetic peripheral neuropathies (DPNs), autonomic neuropathy, painful DPNs, and structural alterations in DPNs.

Duloxetine for the treatment of fibromyalgia

This article presents a brief review of the physiologic abnormalities seen in fibromyalgia, current theories of widespread pain, and treatment options, including emerging therapeutics, with a focus on the use of duloxetine to manage fibromyalgia symptoms. Major clinical trials that examine the efficacy and effectiveness of duloxetine to date are reviewed, and safety issues are discussed.

Duloxetine: a review of its safety and efficacy in the management of fibromyalgia syndrome

Fibromyalgia (FM) is a chronic disorder characterized by widespread pain and other associated symptoms including fatigue, insomnia, cognitive/memory problems, and even psychological distress. Duloxetine is one of three FDA approved medications (the other two being milnacipran and pregabalin) for the treatment of FM. It has been demonstrated that FM patients possess low central nervous system levels of serotonin and norepinephrine. Duloxetine, which is classified pharmacologically as a serotonin-norepinephrine reuptake inhibitor (SNRI), may be beneficial for FM patients by increasing these levels. This review will touch briefly upon the pathophysiology of FM, diagnostic tools, currently available therapeutic options (both pharmacologic and non-pharmacologic), as well as the pharmacokinetic/pharmacodynamic properties of duloxetine. In addition, the efficacy and safety/tolerability of duloxetine exclusively in FM will be assessed through examination of 5 randomized controlled trials, as well as pooled analyses of current data. Suggestions for a therapeutic niche for duloxetine in FM are discussed based on a presentation of the characteristics of duloxetine.

Drug therapy for chronic idiopathic axonal polyneuropathy

BACKGROUND

Chronic idiopathic axonal polyneuropathy is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, it reduces quality of life.

OBJECTIVES

To assess whether drug therapy for chronic idiopathic axonal polyneuropathy reduces disability, ameliorates neurological symptoms and associated impairments, and whether treatment is safe.

SEARCH STRATEGY

We searched Cochrane Library (Cochrane Neuromuscular Disease Review Group Register, Cochrane Database of Systematic Reviews, Cochrane Database of Abstracts of Reviews of Effectiveness, and the Cochrane Central Register of Controlled Trials), MEDLINE, EMBASE, ISI, and ACP Journal Club's Best Evidence, from 1981 until December 2002. We also hand searched the reference lists of relevant articles, reviews and textbooks identified electronically, and contacted authors and other experts in the field to identify additional studies.

SELECTION CRITERIA

We sought all randomised or quasi-randomised (alternate or other systematic treatment allocation), unconfounded trials that examined the effects of any drug therapy in patients with chronic idiopathic axonal polyneuropathy at least one year after the onset of treatment. Patients with chronic idiopathic axonal polyneuropathy had to fulfil the following criteria: age 40 years or older, distal sensory or sensorimotor polyneuropathy, absence of systemic or other neurological disease, chronic clinical course not reaching a nadir in less than two months, exclusion of any recognised cause of the polyneuropathy by medical history taking, clinical or laboratory investigations, electrophysiological studies in agreement with axonal polyneuropathy without evidence of demyelinating features. The primary outcome was the proportion of patients with a significant improvement in disability. Secondary outcomes were change in the mean disability score, change in the proportion of patients who make use of walking aids, change in the mean Medical Research Council sum score, degree of pain relief and/or reduction of other positive sensory symptoms, change in the proportion of patients with pain or other positive sensory symptoms, and frequency of adverse effects.

DATA COLLECTION AND ANALYSIS

Two reviewers independently reviewed and extracted details of trial methodology and outcome data of all potentially relevant trials.

MAIN RESULTS

Eighteen studies were identified and assessed for possible inclusion in the review, but all were excluded because of insufficient quality or lack of relevance.

REVIEWERS' CONCLUSIONS

Even though chronic idiopathic axonal polyneuropathy has been clearly described and delineated, no adequate randomised or quasi-randomised controlled clinical treatment trials have been performed. In their absence there is no proven efficacious drug therapy.