The effect of venlafaxine on ongoing and experimentally induced pain in neuropathic pain patients: a double blind, placebo controlled study

Antidepressants for pain management in adults with chronic pain: a network meta-analysis

BACKGROUND

Chronic pain is common in adults, and often has a detrimental impact upon physical ability, well-being, and quality of life. Previous reviews have shown that certain antidepressants may be effective in reducing pain with some benefit in improving patients' global impression of change for certain chronic pain conditions. However, there has not been a network meta-analysis (NMA) examining all antidepressants across all chronic pain conditions.

OBJECTIVES

To assess the comparative efficacy and safety of antidepressants for adults with chronic pain (except headache).

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, LILACS, AMED and PsycINFO databases, and clinical trials registries, for randomised controlled trials (RCTs) of antidepressants for chronic pain conditions in January 2022.

SELECTION CRITERIA

We included RCTs that examined antidepressants for chronic pain against any comparator. If the comparator was placebo, another medication, another antidepressant, or the same antidepressant at different doses, then we required the study to be double-blind. We included RCTs with active comparators that were unable to be double-blinded (e.g. psychotherapy) but rated them as high risk of bias. We excluded RCTs where the follow-up was less than two weeks and those with fewer than 10 participants in each arm.  DATA COLLECTION AND ANALYSIS: Two review authors separately screened, data extracted, and judged risk of bias. We synthesised the data using Bayesian NMA and pairwise meta-analyses for each outcome and ranked the antidepressants in terms of their effectiveness using the surface under the cumulative ranking curve (SUCRA). We primarily used Confidence in Meta-Analysis (CINeMA) and Risk of Bias due to Missing Evidence in Network meta-analysis (ROB-MEN) to assess the certainty of the evidence. Where it was not possible to use CINeMA and ROB-MEN due to the complexity of the networks, we used GRADE to assess the certainty of the evidence. Our primary outcomes were substantial (50%) pain relief, pain intensity, mood, and adverse events. Our secondary outcomes were moderate pain relief (30%), physical function, sleep, quality of life, Patient Global Impression of Change (PGIC), serious adverse events, and withdrawal.

MAIN RESULTS

This review and NMA included 176 studies with a total of 28,664 participants. The majority of studies were placebo-controlled (83), and parallel-armed (141). The most common pain conditions examined were fibromyalgia (59 studies); neuropathic pain (49 studies) and musculoskeletal pain (40 studies). The average length of RCTs was 10 weeks. Seven studies provided no useable data and were omitted from the NMA. The majority of studies measured short-term outcomes only and excluded people with low mood and other mental health conditions. Across efficacy outcomes, duloxetine was consistently the highest-ranked antidepressant with moderate- to high-certainty evidence. In duloxetine studies, standard dose was equally efficacious as high dose for the majority of outcomes. Milnacipran was often ranked as the next most efficacious antidepressant, although the certainty of evidence was lower than that of duloxetine. There was insufficient evidence to draw robust conclusions for the efficacy and safety of any other antidepressant for chronic pain.  Primary efficacy outcomes Duloxetine standard dose (60 mg) showed a small to moderate effect for substantial pain relief (odds ratio (OR) 1.91, 95% confidence interval (CI) 1.69 to 2.17; 16 studies, 4490 participants; moderate-certainty evidence) and continuous pain intensity (standardised mean difference (SMD) -0.31, 95% CI -0.39 to -0.24; 18 studies, 4959 participants; moderate-certainty evidence). For pain intensity, milnacipran standard dose (100 mg) also showed a small effect (SMD -0.22, 95% CI -0.39 to 0.06; 4 studies, 1866 participants; moderate-certainty evidence). Mirtazapine (30 mg) had a moderate effect on mood (SMD -0.5, 95% CI -0.78 to -0.22; 1 study, 406 participants; low-certainty evidence), while duloxetine showed a small effect (SMD -0.16, 95% CI -0.22 to -0.1; 26 studies, 7952 participants; moderate-certainty evidence); however it is important to note that most studies excluded participants with mental health conditions, and so average anxiety and depression scores tended to be in the 'normal' or 'subclinical' ranges at baseline already. Secondary efficacy outcomes Across all secondary efficacy outcomes (moderate pain relief, physical function, sleep, quality of life, and PGIC), duloxetine and milnacipran were the highest-ranked antidepressants with moderate-certainty evidence, although effects were small. For both duloxetine and milnacipran, standard doses were as efficacious as high doses. Safety There was very low-certainty evidence for all safety outcomes (adverse events, serious adverse events, and withdrawal) across all antidepressants. We cannot draw any reliable conclusions from the NMAs for these outcomes.

AUTHORS' CONCLUSIONS

Our review and NMAs show that despite studies investigating 25 different antidepressants, the only antidepressant we are certain about for the treatment of chronic pain is duloxetine. Duloxetine was moderately efficacious across all outcomes at standard dose. There is also promising evidence for milnacipran, although further high-quality research is needed to be confident in these conclusions. Evidence for all other antidepressants was low certainty. As RCTs excluded people with low mood, we were unable to establish the effects of antidepressants for people with chronic pain and depression. There is currently no reliable evidence for the long-term efficacy of any antidepressant, and no reliable evidence for the safety of antidepressants for chronic pain at any time point.

An Active Inference Account of Touch and Verbal Communication in Therapy

This paper offers theoretical explanations for why “guided touch” or manual touch with verbal communication can be an effective way of treating the body (e.g., chronic pain) and the mind (e.g., emotional disorders). The active inference theory suggests that chronic pain and emotional disorders can be attributed to distorted and exaggerated patterns of interoceptive and proprioceptive inference. We propose that the nature of active inference is abductive. As such, to rectify aberrant active inference processes, we should change the “Rule” of abduction, or the “prior beliefs” entailed by a patient’s generative model. This means pre-existing generative models should be replaced with new models. To facilitate such replacement—or updating—the present treatment proposes that we should weaken prior beliefs, especially the one at the top level of hierarchical generative models, thereby altering the sense of agency, and redeploying attention. Then, a new prior belief can be installed through inner communication along with manual touch. The present paper proposes several hypotheses for possible experimental studies. If touch with verbal guidance is proven to be effective, this would demonstrate the relevance of active inference and the implicit prediction model at a behavioral level. Furthermore, it would open new possibilities of employing inner communication interventions, including self-talk training, for a wide range of psychological and physical therapies.

Neuropharmacological basis for multimodal analgesia in chronic pain

Managing chronic pain remains a major unmet clinical challenge. Patients can be treated with a range of interventions, but pharmacotherapy is the most common. These include opioids, antidepressants, calcium channel modulators, sodium channel blockers, and nonsteroidal anti-inflammatory drugs. Many of these drugs target a particular mechanism; however, chronic pain in many diseases is multifactorial and induces plasticity throughout the sensory neuroaxis. Furthermore, comorbidities such as depression, anxiety, and sleep disturbances worsen quality of life. Given the complexity of mechanisms and symptoms in patients, it is unsurprising that many fail to achieve adequate pain relief from a single agent. The efforts to develop novel drug classes with better efficacy have not always proved successful; a multimodal or combination approach to analgesia is an important strategy in pain control. Many patients frequently take more than one medication, but high-quality evidence to support various combinations is often sparse. Ideally, combining drugs would produce synergistic action to maximize analgesia and reduce side effects, although sub-additive and additive analgesia is still advantageous if additive side-effects can be avoided. In this review, we discuss pain mechanisms, drug actions, and the rationale for mechanism-led treatment selection.Abbreviations: COX - cyclooxygenase, CGRP - calcitonin gene-related peptide, CPM - conditioned pain modulation, NGF - nerve growth factor, NNT - number needed to treat, NMDA - N-methyl-d-aspartate, NSAID - nonsteroidal anti-inflammatory drugs, TCA - tricyclic antidepressant, SNRI - serotonin-noradrenaline reuptake inhibitor, QST - quantitative sensory testing.

Methodology and applicability of the human contact burn injury model: A systematic review

The contact burn injury model is an experimental contact thermode-based physiological pain model primarily applied in research of drug efficacy in humans. The employment of the contact burn injury model across studies has been inconsistent regarding essential methodological variables, challenging the validity of the model. This systematic review analyzes methodologies, outcomes, and research applications of the contact burn injury model. Based on these results, we propose an improved contact burn injury testing paradigm. A literature search was conducted (15-JUL-2020) using PubMed, EMBASE, Web of Science, and Google Scholar. Sixty-four studies were included. The contact burn injury model induced consistent levels of primary and secondary hyperalgesia. However, the analyses revealed variations in the methodology of the contact burn injury heating paradigm and the post-burn application of test stimuli. The contact burn injury model had limited testing sensitivity in demonstrating analgesic efficacy. There was a weak correlation between experimental and clinical pain intensity variables. The data analysis was limited by the methodological heterogenicity of the different studies and a high risk of bias across the studies. In conclusion, although the contact burn injury model provides robust hyperalgesia, it has limited efficacy in testing analgesic drug response. Recommendations for future use of the model are being provided, but further research is needed to improve the sensitivity of the contact burn injury method. The protocol for this review has been published in PROSPERO (ID: CRD42019133734).

Endogenous Pain Modulation Profiles Among Individuals With Chronic Pain: Relation to Opioid Use

It is generally assumed that individuals exhibiting high pain inhibition also tend to exhibit low pain facilitation, but little research has examined this association in individuals with pain. The aims of this cross-sectional study were 1) to examine the association between measures of conditioned pain modulation (CPM) and temporal summation (TS) in individuals with chronic pain, and 2) to examine whether this association was moderated by demographic (age, sex), psychological (depression, catastrophizing), or medication-related (opioid use) variables. Individuals (N= 190) with back or neck pain completed questionnaires and underwent a series of quantitative sensory testing procedures assessing CPM and TS. Results indicated that individuals with higher levels of CPM showed lower levels of TS, r = -.20, P < .01. Analyses, however, revealed that the magnitude of this association was substantially weaker among opioid users (r= -.08, NS) than nonusers (r= -.34, P < .01). None of the demographic or psychological variables included in our study influenced the association between CPM and TS. The magnitude of CPM was lower for opioid users than nonusers, suggesting that opioid use might dampen the functioning of endogenous pain-inhibitory systems and possibly contribute to a discordance between measures of pain inhibition and pain facilitation. PERSPECTIVE: Results of the present study indicated that greater endogenous pain-inhibitory capacity is associated with lower levels of pain facilitation. This association, however, was not significant among opioid users, suggesting that opioids might compromise the functioning and interrelationship between endogenous pain modulatory systems.

The analgesic effect of intravenous methylprednisolone on acute neuropathic pain with allodynia due to central cord syndrome: a retrospective study

Background

Central cord syndrome (CCS) may be associated with severe neuropathic pain that often resists to conventional pain therapy regimens and affects the patients’ quality of life (QoL) seriously. Current treatments for CCS-associated neuropathic pain have limited evidence of efficacy. This retrospective study was performed to present the effects of early treatment with methylprednisolone (MP) on acute neuropathic pain relief and the QoL in CCS patients.

Patients and methods

Data were collected from the medical records of CCS patients who suffered from acute neuropathic pain with allodynia. All the patients received intravenous MP treatment for up to 1 week. Patients were evaluated with standard measures of efficacy: neuropathic pain intensity, the area of allodynia, and the QoL at baseline, daily treatment, and at 1 and 3 months after the end of MP treatment.

Results

Thirty-four eligible patients were enrolled in our study. By the end of MP treatment, the proportion of patients who gained total or major (visual analog scale [VAS] score decreased by 50% or more) allodynia relief from the treatment was 91.18%, and a decrease in spontaneous pain was also observed. Moreover, this study showed MP could significantly improve the QoL of patients based on McGill Pain Questionnaire Short Form and EuroQol Five Dimensions Questionnaire. Four patients (11.76%) during MP treatment experienced mild or moderate side effects. None of the patients manifested CCS-associated neuropathic pain recurrence and MP-associated side effects at follow-up.

Conclusion

The current results suggested that MP offered an effective therapeutic alternative for relieving CCS-associated acute neuropathic pain with allodynia. Given the encouraging results of this study, it would be worthwhile to confirm these results in randomized placebo-controlled clinical trials.

Treatment of Neuropathic Pain with Venlafaxine: A Systematic Review

Objective

To investigate the efficacy of venlafaxine for neuropathic pain and review literature to determine if the medication provides adequate neuropathic pain relief.

Methods

Literature was reviewed on MEDLINE using various key words. These key words include: "venlafaxine and pain," "venlafaxine ER and pain," "venlafaxine XR and pain," "venlafaxine and neuropathic pain," "venlafaxine and neuropathy," "SSRI and neuropathic pain," "SSRI and neuropathy," "SNRI and neuropathic pain," "SNRI and neuropathy," "serotonin reuptake inhibitor and neuropathic pain," "serotonin reuptake inhibitor and neuropathy," "serotonin norepinephrine reuptake inhibitor and neuropathic pain" and "serotonin norepinephrine reuptake inhibitor and neuropathy." Using this guideline, 13 articles were reviewed.

Results

A total of 13 studies reviewed, which are organized by date and diagnosis. It is evident that in the majority of studies, when compared with a placebo, there was a clinical significant reduction in neuropathic pain relief when using venlafaxine. Additionally, one study showed even more significant pain relief when using higher doses of venlafaxine (at least 150 mg). However, when compared with alternative neuropathic medications, venlafaxine for the most part did not perform any better in terms of efficacy.

Conclusion

In conclusion, venlafaxine is a safe and well-tolerated analgesic drug for the symptomatic treatment of neuropathic pain, and there is limited evidence that high-dose venlafaxine (150 mg/day) can be even more beneficial. While the present evidence is quite encouraging regarding venlafaxine's use for neuropathic pain, further research is needed to continue to expand on these findings, particularly when in consideration with other possible pharmacological agents.

Assessment and manifestation of central sensitisation across different chronic pain conditions

Different neuroplastic processes can occur along the nociceptive pathways and may be important in the transition from acute to chronic pain and for diagnosis and development of optimal management strategies. The neuroplastic processes may result in gain (sensitisation) or loss (desensitisation) of function in relation to the incoming nociceptive signals. Such processes play important roles in chronic pain, and although the clinical manifestations differ across condition processes, they share some common mechanistic features. The fundamental understanding and quantitative assessment of particularly some of the central sensitisation mechanisms can be translated from preclinical studies into the clinic. The clinical perspectives are implementation of such novel information into diagnostics, mechanistic phenotyping, prevention, personalised treatment, and drug development. The aims of this paper are to introduce and discuss (1) some common fundamental central pain mechanisms, (2) how they may translate into the clinical signs and symptoms across different chronic pain conditions, (3) how to evaluate gain and loss of function using quantitative pain assessment tools, and (4) the implications for optimising prevention and management of pain. The chronic pain conditions selected for the paper are neuropathic pain in general, musculoskeletal pain (chronic low back pain and osteoarthritic pain in particular), and visceral pain (irritable bowel syndrome in particular). The translational mechanisms addressed are local and widespread sensitisation, central summation, and descending pain modulation.

Significance

Central sensitisation is an important manifestation involved in many different chronic pain conditions. Central sensitisation can be different to assess and evaluate as the manifestations vary from pain condition to pain condition. Understanding central sensitisation may promote better profiling and diagnosis of pain patients and development of new regimes for mechanism based therapy. Some of the mechanisms underlying central sensitisation can be translated from animals to humans providing new options in development of therapies and profiling drugs under development.

Adverse Effects of Antidepressants for Chronic Pain: A Systematic Review and Meta-analysis

Background

Antidepressants are widely used in the treatment of chronic pain. Applied doses are lower than those needed to unfold an antidepressive effect. While efficacy of antidepressants for chronic pain has been reported in large randomized-controlled trials (RCT), there is inconsistent data on adverse effects and tolerability. We aimed at synthesizing data from RCT to explore adverse effect profiles and tolerability of antidepressants for treatment of chronic pain.

Methods

Systematic literature research and meta-analyses were performed regarding side effects and safety of different antidepressants in the treatment of chronic pain according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The National Center for Biotechnology Information library and MEDLINE were searched. Randomized placebo-controlled trials were included in quantitative data synthesis.

Results

Out of 1,975 screened articles, 33 papers published between 1995 and 2015 were included in our review and 23 studies were included in the meta-analyses. A higher risk for adverse effects compared to placebo was observed in all antidepressants included in our analyses, except nortriptyline. The most prevalent adverse effects were dry mouth, dizziness, nausea, headache, and constipation. Amitriptyline, mirtazapine, desipramine, venlafaxine, fluoxetine, and nortriptyline showed the highest placebo effect-adjusted risk of adverse effects. Risk for withdrawal due to adverse effects was highest in desipramine (risk ratio: 4.09, 95%-confidence interval [1.31; 12.82]) followed by milnacipran, venlafaxine, and duloxetine. The most common adverse effects under treatment with antidepressants were dry mouth, dizziness, nausea, headache, and constipation followed by palpitations, sweating, and drowsiness. However, overall tolerability was high. Each antidepressant showed distinct risk profiles of adverse effects.

Conclusion

Our synthesized data analysis confirmed overall tolerability of low-dose antidepressants for the treatment of chronic pain and revealed drug specific risk profiles. This encompassing characterization of adverse effect profiles might be useful in defining multimodal treatment regimens for chronic pain which also consider patients’ comorbidities and co-medication.

Management of Pain Associated with Selected Conditions in Dermatology

Dermatologists face a wide range of pain control challenges in daily practice, from the transient pain of dermatologic surgery to the persistent pain that plagues some chronic dermatologic conditions. Although the pathophysiology of pain is well described and the profound impact of dermatological pain on patients' quality of life is well appreciated, there is an identified need for clear therapeutic plans for providing symptomatic pain relief of common painful dermatoses. In this paper, we will review and clearly outline approaches to pain management of a number of common painful dermatoses such as herpes zoster and post-herpetic neuralgia, ulcers, oral dermatoses, dysesthesias, and many others.

Evidence and clinical considerations for the use of serotonin and norepinephrine reuptake inhibitors for the treatment of painful neuropathy

Introduction

Peripheral neuropathy is a painful condition that can lead to a reduction in quality of life. The pain, which stems from damaged, hyperexcitable neurons, does not respond to traditional analgesics. However, due to the underlying mechanism of pain, some antidepressants are effective in managing peripheral neuropathy. The purpose of this review is to evaluate the available literature on serotonin-norepinephrine reuptake inhibitors for the management of peripheral neuropathy and outline clinical considerations for choosing an agent.

Methods

PubMed, Ovid/MEDLINE, and Scopus queries were conducted for relevant literature. Search types were limited to keyword searches and articles were limited to those published prior to March 31, 2015.

Results

There were 19 randomized controlled trials included in this review. No articles were found investigating the use of desvenlafaxine, milnacipran, or levomilnacipran for treatment of neuropathy. Both duloxetine and venlafaxine improved pain severity scores for patients suffering from painful peripheral neuropathy compared to placebo.

Discussion

Duloxetine and venlafaxine are able to decrease the severity of peripheral neuropathic pain. None of the trials found that either one of the therapies was able to completely eliminate pain for the patients, which should be an important counseling point for patients to understand. Additionally, patient-specific factors should be considered when choosing an agent, including comorbid disease states and potentially interacting medications.

Venlafaxine for neuropathic pain in adults

BACKGROUND

Neuropathic pain, which is caused by nerve damage, is increasing in prevalence worldwide. This may reflect improved diagnosis, or it may be due to increased incidence of diabetes-associated neuropathy, linked to increasing levels of obesity. Other types of neuropathic pain include post-herpetic neuralgia, trigeminal neuralgia, and neuralgia caused by chemotherapy. Antidepressant drugs are sometimes used to treat neuropathic pain; however, their analgesic efficacy is unclear. A previous Cochrane review that included all antidepressants for neuropathic pain is being replaced by new reviews of individual drugs examining chronic neuropathic pain in the first instance. Venlafaxine is a reasonably well-tolerated antidepressant and is a serotonin reuptake inhibitor and weak noradrenaline reuptake inhibitor. Although not licensed for the treatment of chronic or neuropathic pain in most countries, it is sometimes used for this indication.

OBJECTIVES

To assess the analgesic efficacy of, and the adverse effects associated with the clinical use of, venlafaxine for chronic neuropathic pain in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via The Cochrane Library, and MEDLINE and EMBASE via Ovid up to 14 August 2014. We reviewed the bibliographies of any randomised trials identified and review articles, contacted authors of one excluded study and searched www.clinicaltrials.gov to identify additional published or unpublished data. We also searched the meta-Register of controlled trials (mRCT) (www.controlled-trials.com/mrct) and the WHO International Clinical Trials Registry Platform (ICTRP) (apps.who.int/trialsearch/) for ongoing trials but did not find any relevant trials.

SELECTION CRITERIA

We included randomised, double-blind studies of at least two weeks' duration comparing venlafaxine with either placebo or another active treatment in chronic neuropathic pain in adults. All participants were aged 18 years or over and all included studies had at least 10 participants per treatment arm. We only included studies with full journal publication.

DATA COLLECTION AND ANALYSIS

Three review authors independently extracted data using a standard form and assessed study quality. We intend to analyse data in three tiers of evidence as described by Hearn 2014, but did not find any first-tier evidence (ie evidence meeting current best standards, with minimal risk of bias) or second-tier evidence, that was considered at some risk of bias but with adequate participant numbers (at least 200 in the comparison). Third-tier evidence is that arising from studies with small numbers of participants; studies of short duration, studies that are likely to be of limited clinical utility due to other limitations, including selection bias and attrition bias; or a combination of these.

MAIN RESULTS

We found six randomised, double-blind trials of at least two weeks' duration eligible for inclusion. These trials included 460 participants with neuropathic pain, with most participants having painful diabetic neuropathy. Four studies were of cross-over design and two were parallel trials. Only one trial was both parallel design and placebo-controlled. Mean age of participants ranged from 48 to 59 years. In three studies (Forssell 2004, Jia 2006 and Tasmuth 2002), only mean data were reported. Comparators included placebo, imipramine, and carbamazepine and duration of treatment ranged from two to eight weeks. The risk of bias was considerable overall in the review, especially due to the small size of most studies and due to attrition bias. Four of the six studies reported some positive benefit for venlafaxine. In the largest study by Rowbotham, 2004, 56% of participants receiving venlafaxine 150 to 225 mg achieved at least a 50% reduction in pain intensity versus 34% of participants in the placebo group and the number needed to treat for an additional beneficial outcome was 4.5. However, this study was subject to significant selection bias. Known adverse effects of venlafaxine, including somnolence, dizziness, and mild gastrointestinal problems, were reported in all studies but were not particularly problematic and, overall, adverse effects were equally prominent in placebo or other active comparator groups.

AUTHORS' CONCLUSIONS

We found little compelling evidence to support the use of venlafaxine in neuropathic pain. While there was some third-tier evidence of benefit, this arose from studies that had methodological limitations and considerable risk of bias. Placebo effects were notably strong in several studies. Given that effective drug treatments for neuropathic pain are in current use, there is no evidence to revise prescribing guidelines to promote the use of venlafaxine in neuropathic pain. Although venlafaxine was generally reasonably well tolerated, there was some evidence that it can precipitate fatigue, somnolence, nausea, and dizziness in a minority of people.

Design and synthesis of 4-benzylpiperidine carboxamides as dual serotonin and norepinephrine reuptake inhibitors

A series of 4-benzylpiperidine carboxamides were designed and synthesized, and tested for their dual (serotonin and norepinephrine) reuptake inhibition. The synthesis of 4-benzylpiperidine carboxamides involved two main steps: amidation and substitution. Derivatives with 3 carbon linker displayed better activity than with 2 carbon linker. 4-Biphenyl- and 2-naphthyl-substituted derivatives 7e and 7j showed greater dual reuptake inhibition than standard drug venlafaxine HCl.

Review of antidepressants in the treatment of neuropathic pain

Introduction

Neuropathy is a pathological pain disorder characterized by burning, stabbing, and cramping sensations. There are multiple etiologies for this pain such as diabetes, vascular disorders, and chemotherapy treatment. Neurotransmitters, such as norepinephrine and serotonin, are thought to play a part in the modulation of this pain. The objective of this review is to summarize the current literature to support the efficacy and impact of adverse events of the various classes of antidepressants utilized in the treatment of neuropathic pain.

Methods

A Medline/Pubmed search was conducted to identify randomized clinical trials within the last 12 years examining the efficacy and safety of antidepressants for the treatment of neuropathy. Systematic reviews and meta-analyses were also included.

Results

Antidepressants are commonly used in the treatment of neuropathy, with meta-analyses supporting the use of tricyclic antidepressants and selective norepinephrine serotonin reuptake inhibitors. Trials indicate that venlafaxine, duloxetine, and tricyclic antidepressants (TCAs) have comparable efficacy, but TCAs have a higher incidence of adverse effects. Other antidepressants, such as citalopram, paroxetine, and bupropion have limited evidence supporting their use in neuropathy.

Discussion

Based on the evidence reviewed, venlafaxine and duloxetine should be used as first-line agents. TCAs should be used as second-line agents, due to higher incidence of adverse effects. Other treatment options include citalopram, paroxetine, and bupropion, but data supporting their efficacy is limited.

Allodynia and hyperalgesia in neuropathic pain: clinical manifestations and mechanisms

Allodynia (pain due to a stimulus that does not usually provoke pain) and hyperalgesia (increased pain from a stimulus that usually provokes pain) are prominent symptoms in patients with neuropathic pain. Both are seen in various peripheral neuropathies and central pain disorders, and affect 15-50% of patients with neuropathic pain. Allodynia and hyperalgesia are classified according to the sensory modality (touch, pressure, pinprick, cold, and heat) that is used to elicit the sensation. Peripheral sensitisation and maladaptive central changes contribute to the generation and maintenance of these reactions, with separate mechanisms in different subtypes of allodynia and hyperalgesia. Pain intensity and relief are important measures in clinical pain studies, but might be insufficient to capture the complexity of the pain experience. Better understanding of allodynia and hyperalgesia might provide clues to the underlying pathophysiology of neuropathic pain and, as such, they represent new or additional endpoints in pain trials.

Discovery of a potent, dual serotonin and norepinephrine reuptake inhibitor

The objective of the described research effort was to identify a novel serotonin and norepinephrine reuptake inhibitor (SNRI) with improved norepinephrine transporter activity and acceptable metabolic stability and exhibiting minimal drug-drug interaction. We describe herein the discovery of a series of 3-substituted pyrrolidines, exemplified by compound 1. Compound 1 is a selective SNRI in vitro and in vivo, has favorable ADME properties, and retains inhibitory activity in the formalin model of pain behavior. Compound 1 thus represents a potential new probe to explore utility of SNRIs in central nervous system disorders, including chronic pain conditions.

Quantitative sensory testing of neuropathic pain patients: potential mechanistic and therapeutic implications

Quantitative sensory testing (QST) is a widely accepted tool to investigate somatosensory changes in pain patients. Many different protocols have been developed in clinical pain research within recent years. In this review, we provide an overview of QST and tested neuroanatomical pathways, including peripheral and central structures. Based on research studies using animal and human surrogate models of neuropathic pain, possible underlying mechanisms of chronic pain are discussed. Clinically, QST may be useful for 1) the identification of subgroups of patients with different underlying pain mechanisms; 2) prediction of therapeutic outcomes; and 3) quantification of therapeutic interventions in pain therapy. Combined with sensory mapping, QST may provide useful information on the site of neural damage and on mechanisms of positive and negative somatosensory abnormalities. The use of QST in individual patients for diagnostic purposes leading to individualized therapy is an interesting concept, but needs further validation.

Long-term potentiation in spinal nociceptive pathways as a novel target for pain therapy

Long-term potentiation (LTP) in nociceptive spinal pathways shares several features with hyperalgesia and has been proposed to be a cellular mechanism of pain amplification in acute and chronic pain states. Spinal LTP is typically induced by noxious input and has therefore been hypothesized to contribute to acute postoperative pain and to forms of chronic pain that develop from an initial painful event, peripheral inflammation or neuropathy. Under this assumption, preventing LTP induction may help to prevent the development of exaggerated postoperative pain and reversing established LTP may help to treat patients who have an LTP component to their chronic pain. Spinal LTP is also induced by abrupt opioid withdrawal, making it a possible mechanism of some forms of opioid-induced hyperalgesia. Here, we give an overview of targets for preventing LTP induction and modifying established LTP as identified in animal studies. We discuss which of the various symptoms of human experimental and clinical pain may be manifestations of spinal LTP, review the pharmacology of these possible human LTP manifestations and compare it to the pharmacology of spinal LTP in rodents.

The evidence for pharmacological treatment of neuropathic pain

Randomized, double-blind, placebo-controlled trials on neuropathic pain treatment are accumulating, so an updated review of the available evidence is needed. Studies were identified using MEDLINE and EMBASE searches. Numbers needed to treat (NNT) and numbers needed to harm (NNH) values were used to compare the efficacy and safety of different treatments for a number of neuropathic pain conditions. One hundred and seventy-four studies were included, representing a 66% increase in published randomized, placebo-controlled trials in the last 5 years. Painful poly-neuropathy (most often due to diabetes) was examined in 69 studies, postherpetic neuralgia in 23, while peripheral nerve injury, central pain, HIV neuropathy, and trigeminal neuralgia were less often studied. Tricyclic antidepressants, serotonin noradrenaline reuptake inhibitors, the anticonvulsants gabapentin and pregabalin, and opioids are the drug classes for which there is the best evidence for a clinical relevant effect. Despite a 66% increase in published trials only a limited improvement of neuropathic pain treatment has been obtained. A large proportion of neuropathic pain patients are left with insufficient pain relief. This fact calls for other treatment options to target chronic neuropathic pain. Large-scale drug trials that aim to identify possible subgroups of patients who are likely to respond to specific drugs are needed to test the hypothesis that a mechanism-based classification may help improve treatment of the individual patients.

A review of SSRIs and SNRIs in neuropathic pain

IMPORTANCE OF THE FIELD

Selective serotonin reuptake inhibitors (SSRIs) and serotonin noradrenaline reuptake inhibitors (SNRIs) are becoming increasingly used in the treatment of neuropathic pain and fibromyalgia. However, they are not without adverse effects and their efficacy has not been clear because of conflicting evidence.

AREAS COVERED IN THIS REVIEW

We have examined the current evidence on the efficacy of SSRIs and SNRIs in the treatment of neuropathic pain and fibromyalgia. Relevant randomized, placebo-controlled studies were identified through a MEDLINE search of English-language literature from January 1990 to December 2009.

WHAT THE READER WILL GAIN

The evidence for efficacy of SSRIs in the treatment neuropathic pain is moderate at best. However, SNRIs, venlafaxine and duloxetine have been shown to be effective in the treatment of painful diabetic neuropathy and polyneuropathy. With fibromyalgia, both SSRIs (fluoxetine and paroxetine) and SNRIs (duloxetine and milnacipran) have been shown to improve pain relief, function and quality of life.

TAKE HOME MESSAGE

SSRIs and SNRIs may be considered in the treatment of neuropathic pain if treatment with tricyclic antidepressants and anticonvulsants fails, or if there are contraindications to these drugs. There is also sufficient evidence to indicate that SNRIs are effective in the treatment of fibromyalgia and may be considered early in the treatment of fibromyalgia.

Escitalopram and venlafaxine for the prophylaxis of migraine headache without mood disorders

There is evidence that some antidepressant drugs are beneficial in the prophylaxis of migraine. Previous reports have shown that migraine patients may respond to various antidepressant agents used for prophylactic therapy. The main purpose of this study was to compare the efficacy of antidepressants from 2 different groups (venlafaxine vs escitalopram) on people who had migraine headache without depression or anxiety. In this prospective study, we evaluated the headache diaries of 93 patients who were being treated with venlafaxine (n = 35) and escitalopram (n = 58). At the end of the 3-month period, patients were reassessed, and those with marked differences in attack frequency, duration, intensity (with visual analog scales), lost work-day equivalent index, and migraine disability assessment questionnaire were compared. There was a clear reduction in headache frequency (P < 0.0001), duration (P < 0.0001), and severity (P < 0.0001) in the venlafaxine group. In addition, there was a significant improvement in daily work performance during headaches (P < 0.0001). In the escitalopram group, monthly headache frequency (P < 0.026), duration (P < 0.002), and intensity (P < 0.027) all decreased significantly, although not to the same extent as with venlafaxine. After the third month of venlafaxine and escitalopram treatment, most of the patients (82.8% vs 96.5%) were seen to have moved to the minimal or infrequent migraine disability assessment group. According to our findings, venlafaxine and escitalopram are both effective in the prophylaxis of migraine headache without depression and anxiety. This effect was independent of mood disorder. Escitalopram should be the first choice because of its fewer side effects, but venlafaxine may be used if escitalopram is found to be insufficient.

Physician speciality and pain reduction in patients with depressive symptoms under treatment with venlafaxine

OBJECTIVES

Excessive pain perception may lead to unnecessary diagnostic testing or invasive procedures resulting in iatrogenic complications and prolonged disability. Naturalistic studies on patients with chronic pain and depressive symptoms investigating the impact of medical speciality on treatment outcome in a primary care setting are lacking.

METHODS

In this observational study, we examined whether the magnitude of pain reduction in 444 patients with depressive symptomatology under venlafaxine would relate differently to the medical speciality of the 122 treating physicians, namely psychiatrists (n=110 patients), general practitioners (n=236 patients), and internists (n=98 patients).

RESULTS

Independent of age, gender, patient's region of origin, comorbidity, severity and duration of pain, and depressive symptoms at study entry, patients seemed to benefit significantly less in terms of pain reduction (p<0.001) and of reduction in severity of depressive symptomatology by psychiatrists as compared to general practitioners (p<0.019) and internists (p<0.002).

CONCLUSIONS

The findings suggest that patients referred to psychiatrists are more difficult to treat than those referred to general practitioners and internists, and might not have been adequately prepared for psychiatric interventions. A supporting cooperation and networking between psychiatrists and primary care physicians may contribute to an integrated treatment concept and therefore, may lead to a better outcome in this challenging patient group.

EFNS guidelines on the pharmacological treatment of neuropathic pain: 2010 revision

BACKGROUND AND OBJECTIVES

This second European Federation of Neurological Societies Task Force aimed at updating the existing evidence about the pharmacological treatment of neuropathic pain since 2005.

METHODS

Studies were identified using the Cochrane Database and Medline. Trials were classified according to the aetiological condition. All class I and II randomized controlled trials (RCTs) were assessed; lower class studies were considered only in conditions that had no top-level studies. Treatments administered using repeated or single administrations were considered, provided they are feasible in an outpatient setting.

RESULTS

Most large RCTs included patients with diabetic polyneuropathies and post-herpetic neuralgia, while an increasing number of smaller studies explored other conditions. Drugs generally have similar efficacy in various conditions, except in trigeminal neuralgia, chronic radiculopathy and HIV neuropathy, with level A evidence in support of tricyclic antidepressants (TCA), pregabalin, gabapentin, tramadol and opioids (in various conditions), duloxetine, venlafaxine, topical lidocaine and capsaicin patches (in restricted conditions). Combination therapy appears useful for TCA-gabapentin and gabapentin-opioids (level A).

CONCLUSIONS

There are still too few large-scale comparative studies. For future trials, we recommend to assess comorbidities, quality of life, symptoms and signs with standardized tools and attempt to better define responder profiles to specific drug treatments.

Regional origin and decrease of pain in patients with depressive symptoms under treatment with venlafaxine

OBJECTIVE

Patient's language, tradition, conventions, and customs may all determine integration into a society and are also part of the doctor-patient relationship that influences diagnostic and therapeutic outcome. Language barrier and sociocultural disparity of Eastern and Southern European patients may hamper recovery from pain and depression compared to Middle European patients in Switzerland.

METHODS

In a prospective naturalistic observational trial we investigated the influence of regional origin on treatment outcome in 420 pain sufferers with depressive symptoms from all over Switzerland who were treated with venlafaxine by 122 physicians in primary care. Physicians rated severity of depressive symptoms using the clinical global impression severity scale and pain intensity by means of visual analogue scales. We hypothesized that in Eastern and Southern European patients the magnitude of pain reduction under treatment with venlafaxine is less compared to Middle European patients.

RESULTS

Three months after study entry, Middle European patients were found to profit more from treatment with venlafaxine in terms of severity of depression and pain intensity than patients from Eastern Europe and Southern Europe.

CONCLUSION

Regional origin may contribute to the magnitude of pain reduction in patients with depressive symptoms under treatment with venlafaxine. Our results provide a rational for care provider educational programs aimed at improving capacities in treating patients from different regional origin with psychosomatic complaints such as depression and comorbid pain.

Serotonin-norepinephrine reuptake inhibitors for pain control: premise and promise

The precise mechanisms of pain perception and transmission in the central nervous system have not been fully elucidated. However, extensive data support a role for the monoamine neurotransmitters, serotonin and norepinephrine, in the modulation of pain. Experiments with animal models of pain indicate that noradrenergic interventions, and to a lesser extent serotonergic interventions, reduce pain-related behavior. This is supported by data from clinical trials in humans in which antidepressants have been shown to reduce pain and functional impairment in central and neuropathic pain conditions. These effects are particularly well-studied in trials with serotonin-norepinephrine reuptake inhibitors (SNRIs), which have provided a useful tool in the clinician's arsenal, particularly considering the limitations of other classes of pain medications such as opioids, anti-inflammatories, and anticonvulsants (i.e., limited efficacy, safety and tolerability issues). Moreover, painful physical symptoms are frequently comorbid with major psychiatric disorders such as major depressive disorder and anxiety disorders. This paper reviewed and summarized the rationale and potential role of SNRIs for the control of pain including clinical and preclinical background. Currently evidence does not definitely support a role of the SNRIs, while limited data propose a putative promise of SNRIs in the treatment of pain related disorders including fibromyalgia and depressed patients with multiple somatic complaints. More researches are warranted to generalize currently available preliminary evidences.

Psychiatric issues in chronic pain

Chronic pain requires comprehensive care. While interdisciplinary approaches are recommended, the role of psychiatrists is often misunderstood. Psychiatrists should be involved with the care of patients with chronic pain as early as possible to maximize outcome. Psychiatrists offer an expertise that specifically addresses important deficiencies in the care of patients with chronic pain: 1) the lack of a detailed formulation, 2) the lumping of all psychopathology, and 3) the failure to effectively use psychopharmacologic treatments. This review provides a framework for formulating the diagnoses and treatments of patients with chronic pain.

The effect of venlafaxine HCl on painful peripheral diabetic neuropathy in patients with type 2 diabetes mellitus

OBJECTIVE

The objective of this study was to evaluate the efficacy of venlafaxine HCl in the symptomatic treatment of painful peripheral diabetic neuropathy (PPDN) among patients with type 2 diabetes mellitus (DM).

DESIGN

This study was designed as a prospective, randomized, and controlled trial.

SETTING

This study was conducted at the Dicle University Medical Faculty (Diyarbakir, Turkey).

PATIENTS

Sixty type 2 DM outpatients (47 females and 13 males) with PPDN who had a minimum visual analog scale (VAS) score of 40 mm were enrolled in this study.

INTERVENTIONS

Patients randomized to the treatment group (n=30) received venlafaxine HCl, whereas those randomized to the control group (n=30) received a combination of vitamins B(1)and B(6) tablets.

MEASURES

Severity of pain was measured by VAS, Short-Form McGill Pain Questionnaire, and numerical analog scale scores at admission and at the second, fourth, and eighth weeks of the study. Polyneuropathy was supported by electromyelography.

OUTCOME

In the treatment group, severity of pain was measured as 70.0+/-13.0 in the VAS, as 24.9+/-6.2 in the Short-Form McGill Pain Questionnaire, and as 7.2+/-1.1 in the numerical analog scale. In the control group, it was measured as 73.0+/-8.0 in the VAS, as 26.8+/-6.2 in the Short-Form McGill Pain Questionnaire, and as 7.4+/-0.8 in the numerical analog scale (P>.05).

RESULTS

The most common form of PPDN was distal symmetrical sensorimotor polyneuropathy in both groups (46.8% vs. 50.0%). At the end of the study, there was a significant difference in severity of pain between the groups. In the treatment group, scores were 8.5+/-5.2 and 3.1+/-1.6 in the Short-Form McGill Pain Questionnaire and numerical analog scale, respectively; in the control group, these were 20.5+/-7.0 and 5.5+/-1.6, respectively (P<.001).

CONCLUSIONS

Venlafaxine HCl is a safe and well-tolerable analgesic drug in the symptomatic treatment of PPDN; however, it has minimal adverse effects. It showed its efficacy markedly in the second week of therapy.

[Treatment of neuropathic pain in HIV-infected patients]

Neuropathic pain of various etiologies is a frequent symptom in HIV-infected patients that is underdiagnosed and inadequately treated. It requires a multidisciplinary pain approach based on psychosocial factors, diet and exercise, etiologic treatment whenever possible, symptomatic medical treatment, and sometimes, interventional techniques. Medical treatment should be individualized and introduced gradually, with a mind to potential drug interactions. Neuropathic pain responds poorly to conventional analgesics, such as nonsteroidal antiinflammatory drugs and opiates; tricyclic antidepressants and anticonvulsants are the drugs of choice. Before establishing an analgesic treatment, possible drug interactions should be ruled out, mainly those occurring with antiretroviral agents.

Evidence-informed management of chronic low back pain with adjunctive analgesics

The management of chronic low back pain (CLBP) has proven very challenging in North America, as evidenced by its mounting socioeconomic burden. Choosing among available nonsurgical therapies can be overwhelming for many stakeholders, including patients, health providers, policy makers, and third-party payers. Although all parties share a common goal and wish to use limited health-care resources to support interventions most likely to result in clinically meaningful improvements, there is often uncertainty about the most appropriate intervention for a particular patient. To help understand and evaluate the various commonly used nonsurgical approaches to CLBP, the North American Spine Society has sponsored this special focus issue of The Spine Journal, titled Evidence-Informed Management of Chronic Low Back Pain Without Surgery. Articles in this special focus issue were contributed by leading spine practitioners and researchers, who were invited to summarize the best available evidence for a particular intervention and encouraged to make this information accessible to nonexperts. Each of the articles contains five sections (description, theory, evidence of efficacy, harms, and summary) with common subheadings to facilitate comparison across the 24 different interventions profiled in this special focus issue, blending narrative and systematic review methodology as deemed appropriate by the authors. It is hoped that articles in this special focus issue will be informative and aid in decision making for the many stakeholders evaluating nonsurgical interventions for CLBP.

Antidepressants for the treatment of chronic pain

Chronic pain represents one of the most important public health problems and, in addition to classical analgesics, antidepressants are an essential part of the therapeutic strategy. This article reviews available evidence on the efficacy and safety of antidepressants in major chronic pain conditions; namely, neuropathic pain, headaches, low back pain, fibromyalgia, irritable bowel syndrome (IBS) and cancer pain. Studies, reviews and meta-analyses published from 1991 to March 2008 were retrieved through MEDLINE, PsycINFO and the Cochrane database using numerous key words for pain and antidepressants. In summary, evidence supports the use of tricyclic antidepressants in neuropathic pain, headaches, low back pain, fibromyalgia and IBS. The efficacy of the newer serotonin and norepinephrine reuptake inhibitors is less supported by evidence, but can be recommended in neuropathic pain, migraines and fibromyalgia. To date, evidence does not support an analgesic effect of serotonin reuptake inhibitors, but beneficial effects on well-being were reported in several chronic pain conditions. These results are discussed in the light of current insights in the neurobiology of pain, the reciprocal relationship between pain and depression, and future developments in this field of research.

Dopamine D1 and D2 receptor agonism enhances antinociception mediated by the serotonin and noradrenaline reuptake inhibitor duloxetine in the rat formalin test

Altered functioning of monoamine-containing pathways descending from supraspinal structures to the spinal dorsal horn contributes to injury-induced sensitization of nociceptive transmission. Antidepressant drugs as typified by the dual serotonin (5-HT) and noradrenaline reuptake inhibitor duloxetine attenuate various signs and symptoms of persistent pain in animals and humans. The current study assessed whether dopamine receptor agonists could further enhance the antinociceptive activity of duloxetine in an animal model of injury-induced central sensitization, the rat formalin test. Duloxetine (3-100 mg/kg, s.c.), the dopamine D(1) receptor agonist SKF-82958 (0.1-1 mg/kg, s.c.) and the dopamine D(2) receptor agonist quinpirole (0.003-0.1 mg/kg, s.c.) all significantly attenuated spontaneous nociceptive behaviours during the second phase of the test; duloxetine and quinpirole also attenuated nociceptive behaviours during first phase and interphase. These antinociceptive actions of SKF-82958 and quinpirole were selectively antagonized by SCH 23390 and eticlopride respectively. Remarkably, when completely inactive doses of duloxetine (3 mg/kg) and SKF-82958 (0.3 mg/kg) were combined, a marked attenuation of second phase nociceptive behaviours occurred (P<0.05 vs vehicle), indicative of analgesic synergy. Similarly, when an active antinociceptive dose of quinpirole (0.03 mg/kg, P<0.05 vs vehicle) was combined with an inactive dose of duloxetine (3 mg/kg), a potentiation of duloxetine-mediated antinociception was observed (P<0.001 vs vehicle). Taken together, these results suggest that antidepressant drugs that can enhance the activity of 5-HT, noradrenaline and dopamine neurotransmission within nociceptive pathways should provide a broader spectrum of antinociception than dual mechanism of action reuptake inhibitors in animal models of injury-induced persistent nociception.

Pharmacologic management of neuropathic pain: evidence-based recommendations

Patients with neuropathic pain (NP) are challenging to manage and evidence-based clinical recommendations for pharmacologic management are needed. Systematic literature reviews, randomized clinical trials, and existing guidelines were evaluated at a consensus meeting. Medications were considered for recommendation if their efficacy was supported by at least one methodologically-sound, randomized clinical trial (RCT) demonstrating superiority to placebo or a relevant comparison treatment. Recommendations were based on the amount and consistency of evidence, degree of efficacy, safety, and clinical experience of the authors. Available RCTs typically evaluated chronic NP of moderate to severe intensity. Recommended first-line treatments include certain antidepressants (i.e., tricyclic antidepressants and dual reuptake inhibitors of both serotonin and norepinephrine), calcium channel alpha2-delta ligands (i.e., gabapentin and pregabalin), and topical lidocaine. Opioid analgesics and tramadol are recommended as generally second-line treatments that can be considered for first-line use in select clinical circumstances. Other medications that would generally be used as third-line treatments but that could also be used as second-line treatments in some circumstances include certain antiepileptic and antidepressant medications, mexiletine, N-methyl-D-aspartate receptor antagonists, and topical capsaicin. Medication selection should be individualized, considering side effects, potential beneficial or deleterious effects on comorbidities, and whether prompt onset of pain relief is necessary. To date, no medications have demonstrated efficacy in lumbosacral radiculopathy, which is probably the most common type of NP. Long-term studies, head-to-head comparisons between medications, studies involving combinations of medications, and RCTs examining treatment of central NP are lacking and should be a priority for future research.

Antidepressants for neuropathic pain

BACKGROUND

This is an updated version of the original Cochrane review published in Issue 3, 2005 of The Cochrane Library. For many years antidepressant drugs have been used to manage neuropathic pain, and are often the first choice treatment. It is not clear, however, which antidepressant is more effective, what role the newer antidepressants can play in treating neuropathic pain, and what adverse effects are experienced by patients.

OBJECTIVES

To determine the analgesic effectiveness and safety of antidepressant drugs in neuropathic pain.

SEARCH STRATEGY

Randomised controlled trials (RCTs) of antidepressants in neuropathic pain were identified in MEDLINE (1966 to Oct 2005); EMBASE (1980 to Oct 2005); the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, Issue 3, 2005; and the Cochrane Pain, Palliative and Supportive Care Trials Register (May 2002). Additional reports were identified from the reference list of the retrieved papers, and by contacting investigators.

SELECTION CRITERIA

RCTs reporting the analgesic effects of antidepressant drugs in adult patients, with subjective assessment of pain of neuropathic origin. Studies that included patients with chronic headache and migraine were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors agreed the included studies, extracted data, and assessed methodological quality independently. Sixty one trials of 20 antidepressants were considered eligible (3293 participants) for inclusion. Relative Risk (RR) and Number-Needed-to-Treat (NNTs) were calculated from dichotomous data for effectiveness and adverse effects. This update includes 11 additional studies (778 participants).

MAIN RESULTS

Sixty one RCTs were included in total. Tricyclic antidepressants (TCAs) are effective and have an NNT of 3.6 (95% CI 3 to 4.5) RR 2.1 (95% CI 1.8 to 2.5) for the achievement of at least moderate pain relief. There is limited evidence for the effectiveness of the newer SSRIs but no studies of SNRIs were found. Venlafaxine (three studies) has an NNT of 3.1 (95% CI 2.2 to 5.1) RR 2.2 (95% CI 1.5 to 3.1). There were insufficient data to assess effectiveness for other antidepressants such as St Johns Wort and L-tryptophan. For diabetic neuropathy the NNT for effectiveness was 1.3 (95% CI 1.2 to 1.5) RR 12.4 (95% CI 5.2 to 29.2) (five studies); for postherpetic neuralgia 2.7 (95% CI 2 to 4.1), RR 2.2 (95% CI 1.6 to 3.1) (four studies). There was evidence that TCAs are not effective in HIV-related neuropathies. The number needed to harm (NNH) for major adverse effects defined as an event leading to withdrawal from a study was 28 (95% CI 17.6 to 68.9) for amitriptyline and 16.2 (95% CI 8 to 436) for venlafaxine. The NNH for minor adverse effects was 6 (95% CI 4.2 to 10.7) for amitriptyline and 9.6 (95% CI 3.5 to 13) for venlafaxine.

AUTHORS' CONCLUSIONS

This update has provided additional confirmation on the effectiveness of antidepressants for neuropathic pain and has provided new information on another antidepressant - venlafaxine. There is still limited evidence for the role of SSRIs. Whether antidepressants prevent the development of neuropathic pain (pre-emptive use) is still unclear. Both TCAs and venlafaxine have NNTs of approximately three. This means that for approximately every three patients with neuropathic pain who are treated with either of these antidepressants, one will get at least moderate pain relief. There is evidence to suggest that other antidepressants may be effective but numbers of participants are insufficient to calculate robust NNTs. SSRIs are generally better tolerated by patients and more high quality studies are required.