The rationale and use of topiramate for treating neuropathic pain

Habituation to Pain in Patients with Chronic Pain: Clinical Implications and Future Directions

In this review, the latest insights into habituation to pain in chronic pain are summarized. Using a systematic search, results of studies on the evidence of habituation to (experimental) pain in migraine, chronic low back pain, fibromyalgia, and a variety of chronic pain indications are presented. In migraine, reduced habituation based on self-report and the EEG-based N1 and N2-P2 amplitude is reported, but the presence of contradictory results demands further replication in larger, well-designed studies. Habituation to pain in chronic low back pain seems not to differ from controls, with the exception of EEG measures. In fibromyalgia patients, there is some evidence for reduced habituation of the N2-P2 amplitude. Our analysis shows that the variability between outcomes of studies on habituation to pain is high. As the mechanisms underlying habituation to pain are still not fully understood and likely involve several pathways, it is now too early to conclude that habituation to pain is related to clinical outcomes and can be used as a diagnostic marker. The review ends with a discussion on future directions for research including the use of standard outcome measures to improve comparisons of habituation to pain in patients and controls, as well as a focus on individual differences.

Neuropathic ocular surface pain: Emerging drug targets and therapeutic implications

INTRODUCTION

Dysfunction at various levels of the somatosensory system can lead to ocular surface pain with a neuropathic component. Compared to nociceptive pain (due to noxious stimuli at the ocular surface), neuropathic pain tends to be chronic and refractory to therapies, making it an important source of morbidity in the population. An understanding of the options available for neuropathic ocular surface pain, including new and emerging therapies, is thus an important topic.

AREAS COVERED

This review will examine studies focusing on ocular surface pain, emphasizing those examining patients with a neuropathic component. Attention will be placed toward recent (after 2017) studies that have examined new and emerging therapies for neuropathic ocular surface pain.

EXPERT OPINION

Several therapies have been studied thus far, and continued research is needed to identify which individuals would benefit from specific therapies. Gaps in our understanding exist, especially with availability of in-clinic diagnostics for neuropathic pain. A focus on improving diagnostic capabilities and researching gene-modulating therapies could help us to provide more specific mechanism-based therapies for patients. In the meantime, continuing to uncover new modalities and examining which are likely to work depending on pain phenotype remains an important short-term goal.

Patterns and Impact of Electronic Health Records-Defined Depression Phenotypes in Spine Surgery

BACKGROUND

Preoperative depression is a risk factor for poor outcomes after spine surgery.

OBJECTIVE

To understand effects of depression on spine surgery outcomes and healthcare resource utilization.

METHODS

Using IBM's MarketScan Database, we identified 52 480 patients who underwent spinal fusion. Retained patients were classified into 6 depression phenotype groups based on International Classification of Disease, 9th/10th Revision (ICD-9/10) codes and use/nonuse of antidepressant medications: major depressive disorder (MDD), other depression (OthDep), antidepressants for other psychiatric condition (PsychRx), antidepressants for physical (nonpsychiatric) condition (NoPsychRx), psychiatric condition only (PsychOnly), and no depression (NoDep). We analyzed baseline demographics, comorbidities, healthcare utilization/payments, and chronic opioid use.

RESULTS

Breakdown of groups in our cohort: MDD (15%), OthDep (12%), PsychRx (13%), NonPsychRx (15%), PsychOnly (12%), and NoDep (33%). Postsurgery: increased outpatient resource utilization, admissions, and medication refills at 1, 2, and 5 yr in the NoDep, PsychOnly, NonPsychRx, PsychRx, and OthDep groups, and highest in MDD. Postoperative opioid usage rates remained unchanged in MDD (44%) and OthDep (36%), and reduced in PsychRx (40%), NonPsychRx (31%), and PsychOnly (20%), with greatest reduction in NoDep (13%). Reoperation rates: 1 yr after index procedure, MDD, OthDep, PsychRx, NonPsychRx, and PsychOnly had more reoperations compared to NoDep, and same at 2 and 5 yr. In NoDep patients, 45% developed new depressive phenotype postsurgery.

CONCLUSION

EHR-defined classification allowed us to study in depth the effects of depression in spine surgery. This increased understanding of the interplay of mental health will help providers identify cohorts at risk for high complication rates, and health care utilization.

The effects of Topiramate on isolation-induced aggression: a behavioral and immunohistochemical study in mice

Topiramate, an antiepileptic drug, has been found to be useful for the treatment of aggression in clinical populations. Most preclinical studies related to Topiramate have been focused exclusively on the quantitative aspects of the aggressive behavior between mice. However, there is still limited knowledge regarding the effects of Topiramate on neuronal mechanisms occurring in aggressive mice. The present work aims to understand further the effects of the antiepileptic drug Topiramate on aggressive behaviors, and on the neural correlates underlying such behaviors. To achieve this, we combined the resident-intruder model of isolation-induced aggression in mice with two drug regimens of Topiramate administration (30.0 mg/kg; acute and sub-chronic treatments). Our data showed that both acute and subchronic treatments decreased the intensity of agonistic encounters and reinforced social behavior. By using C-fos immunoreactivity, we investigated the neuronal activation of several brain regions involved in aggressive behavior following subchronic treatment. We found that Topiramate produced activation in several cortical areas and in the lateral septum of resident brain mice compared with their controls. However, Topiramate induced inhibition in the medial nucleus of the amygdala, the dorsomedial nucleus of the periaqueductal gray, and especially in the anterior hypothalamic nucleus. Finally, we performed microinfusion of Topiramate (0.1 and 0.3 mM) into the lateral septum and anterior hypothalamus on offensive behaviors in isolation-induced-aggression paradigm. Interestingly, the microinfusion of Topiramate into the lateral septum has the capacity to alleviate aggressive behavior, without affecting social behavior. However, the microinfusion of Topiramate into the anterior hypothalamus decreased aggressive behavior and slightly reinforced social behavior. Our observations supported that the dose of 0.1 mM of Topiramate appeared more efficacy to treat aggression in adult mice. These pharmacological characteristics may account for Topiramate efficacy on aggressive symptoms in psychiatric patients.

Contributions of Nociresponsive Area 3a to Normal and Abnormal Somatosensory Perception

Traditionally, cytoarchitectonic area 3a of primary somatosensory cortex (SI) has been regarded as a proprioceptive relay to motor cortex. However, neuronal spike-train recordings and optical intrinsic signal imaging, obtained from nonhuman sensorimotor cortex, show that neuronal activity in some of the cortical columns in area 3a can be readily triggered by a C-nociceptor afferent drive. These findings indicate that area 3a is a critical link in cerebral cortical encoding of secondary/slow pain. Also, area 3a contributes to abnormal pain processing in the presence of activity-dependent reversal of gamma-aminobutyric acid A receptor-mediated inhibition. Accordingly, abnormal processing within area 3a may contribute mechanistically to generation of clinical pain conditions. PERSPECTIVE: Optical imaging and neurophysiological mapping of area 3a of SI has revealed substantial driving from unmyelinated cutaneous nociceptors, complementing input to areas 3b and 1 of SI from myelinated nociceptors and non-nociceptors. These and related findings force a reconsideration of mechanisms for SI processing of pain.

Brain's compensatory response to drug-induced cognitive impairment

INTRODUCTION

Topiramate (TPM), a frequently prescribed antiseizure medication, can cause severe cognitive side-effects. Though these side-effects have been studied behaviorally, the underlying neural mechanisms are unknown. In a double-blind, randomized, placebo-controlled, crossover study of TPM's impact on cognition, nine healthy volunteers completed three study sessions: a no-drug baseline session and two sessions during which they received either TPM or placebo. Electroencephalogram was recorded during each session while subjects performed a working-memory task with three memory-loads.

RESULTS

Comparing TPM with baseline we found the following results. (a) TPM administration led to declines in behavioral performance. (b) Fronto-central event-related potentials (ERP) elicited by probe stimuli, representing the primary task network activity, showed strong memory-load modulations at baseline, but the magnitude of these load-dependent modulations was significantly reduced during TPM session, suggesting drug-induced impairments of the primary task network. (c) ERP responses over bilateral fronto-temporal electrodes, which were not load sensitive at baseline, showed significant memory-load modulations after TPM administration, suggesting the drug-related recruitment of additional neural resources. (d) At fronto-central scalp sites, there was significant increase in response amplitude for low memory-load during TPM session compared to baseline, and the amplitude increase was dependent on TPM plasma concentration, suggesting that the primary task network became less efficient under TPM impact. (e) At bilateral fronto-temporal electrodes, there were no ERP differences when comparing low memory-load trials, but TPM administration led to an increase in ERP responses to high load, the magnitude of which was positively correlated with task performance, suggesting that the recruited neural resources were beneficial for task performance. Placebo-TPM comparison yielded similar effects albeit with generally reduced significance and effect sizes.

CONCLUSION

Our findings support the hypothesis that TPM impairs the primary task network by reducing its efficiency, which triggers compensatory recruitment of additional resources to maintain task performance.

Comparison of the effect of topiramate versus gabapentin on neuropathic pain in patients with polyneuropathy: A randomized clinical trial

BACKGROUND

Neuropathic pain is one of the most common complaints of neurologic clinics. Neuropathic pain is common and important and has inappropriate complications, and despite their importance, there is no effective treatment for them.

OBJECTIVE

Because of the importance of neuropathic pain and safe and effective treatment, in this study, we determined the effect of topiramate versus gabapentin in patients with neuropathic pain.

METHODS

In this randomized clinical trial, 30 patients with pain attributed to neuropathy who had at least one month of neuropathic pain in one area, were randomized to receive either gabapentin, titrated from 300 mg/day to a maximum of 900 mg/day or topiramate, titrated from 50 mg/day to a maximum of 100 mg/day after a 4-week period in the neurology clinic of Imam Khomeini Hospital of Urmia city, Iran in 2015. Complication, drug tolerance rate and pain were investigated. The pain was measured on visual analog scale (VAS). The data were analyzed by SPSS version 18, and using descriptive statistics, t-test, and ANOVA.

RESULTS

In patients treated by gabapentin, the primary pain score was 74.33±10.29, this score decreased to 49.46±11.41 and 29.93±11.92 in the second and fourth week after intervention with gabapentin. In topiramate treated patients, the primary score was 76.00±9.69. It decreased to 54.33±10.31 and 34.20±6.09 at the same time. There were no significant differences between both groups in terms of average reduction of pain intensity [gabapentin group (59.73%) compared with topiramate (55%) (p=0.48)]. In the present study, the only complication reported in patients treated by gabapentin was drowsiness, but other uncommon side effects were nausea and dizziness.

CONCLUSION

This study showed that both gabapentin and topiramate reduce pain. Topiramate can also be a good alternative choice, if gabapentin has side effects for patients and it cannot be tolerated, topiramate can be a good replacement.

TRIAL REGISTRATION

The trial was registered at the Thai Registry of Clinical Trials (http://www.clinicaltrials.in.th) with the TCTR ID: TCTR20170615001.

FUNDING

This research has been financially supported by Research Council of Urmia University of Medical Sciences.

Antiepileptic drugs for chronic non-cancer pain in children and adolescents

BACKGROUND

Pain is a common feature of childhood and adolescence around the world, and for many young people, that pain is chronic. The World Health Organization (WHO) guidelines for pharmacological treatments for children's persisting pain acknowledge that pain in children is a major public health concern of high significance in most parts of the world. While in the past, pain was largely dismissed and was frequently left untreated, views on children's pain have changed over time, and relief of pain is now seen as importantWe designed a suite of seven reviews on chronic non-cancer pain and cancer pain (looking at antidepressants, antiepileptic drugs, non-steroidal anti-inflammatory drugs, opioids, and paracetamol) in order to review the evidence for children's pain utilising pharmacological interventions in children and adolescents.As the leading cause of morbidity in the world today, chronic disease (and its associated pain) is a major health concern. Chronic pain (that is pain lasting three months or longer) can occur in the paediatric population in a variety of pathophysiological classifications (nociceptive, neuropathic, or idiopathic) relating to genetic conditions, nerve damage pain, chronic musculoskeletal pain, and chronic abdominal pain, and for other unknown reasons.Antiepileptic (anticonvulsant) drugs, which were originally developed to treat convulsions in people with epilepsy, have in recent years been used to provide pain relief in adults for many chronic painful conditions and are now recommended for the treatment of chronic pain in the WHO list of essential medicines. Known side effects of antiepileptic drugs range from sweating, headache, elevated temperature, nausea, and abdominal pain to more serious effects including mental or motor function impairment.

OBJECTIVES

To assess the analgesic efficacy and adverse events of antiepileptic drugs used to treat chronic non-cancer pain in children and adolescents aged between birth and 17 years, in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online, MEDLINE via Ovid, and Embase via Ovid from inception to 6 September 2016. We also searched the reference lists of retrieved studies and reviews as well as online clinical trial registries.

SELECTION CRITERIA

Randomised controlled trials, with or without blinding, by any route, treating chronic non-cancer pain in children and adolescents, comparing any antiepileptic drug with placebo or an active comparator.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility. We planned to use dichotomous data to calculate risk ratio and number needed to treat for one additional event, using standard methods if data were available. We assessed the evidence using GRADE and created two 'Summary of findings' tables.

MAIN RESULTS

We included two studies with a total of 141 participants (aged 7 to 18 years) with chronic neuropathic pain, complex regional pain syndrome type 1 (CRPS-I), or fibromyalgia. One study investigated pregabalin versus placebo in participants with fibromyalgia (107 participants), and the other study investigated gabapentin versus amitriptyline in participants with CRPS-I or neuropathic pain (34 participants). We were unable to perform any quantitative analysis.Risk of bias for the two included studies varied, due to issues with randomisation (low to unclear risk), blinding of outcome assessors (low to unclear risk), reporting bias (low to unclear risk), the size of the study populations (high risk), and industry funding in the 'other' domain (low to unclear risk). We judged the remaining domains of sequence generation, blinding of participants and personnel, and attrition as low risk of bias. Primary outcomesOne study (gabapentin 900 mg/day versus amitriptyline 10 mg/day, 34 participants, for 6 weeks) did not report our primary outcomes (very low-quality evidence).The second study (pregabalin 75 to 450 mg/day versus placebo 75 to 450 mg/day, 107 participants, for 15 weeks) reported no significant change in pain scores for pain relief of 30% or greater between pregabalin 18/54 (33.3%), and placebo 16/51 (31.4%), P = 0.83 (very low-quality evidence). This study also reported Patient Global Impression of Change, with the percentage of participants feeling "much or very much improved" with pregabalin 53.1%, and placebo 29.5% (very low-quality evidence).We downgraded the evidence by three levels to very low for one of two reasons: due to the fact that there was no evidence to support or refute the use of the intervention, or that there were too few data and the number of events was too small to be meaningful. Secondary outcomesIn one small study, adverse events were uncommon: gabapentin 2 participants (2 adverse events); amitriptyline 1 participant (1 adverse event) (6-week trial). The second study reported a higher number of adverse events: pregabalin 38 participants (167 adverse events); placebo 34 participants (132 adverse events) (15-week trial) (very low-quality evidence).Withdrawals due to adverse events were infrequent in both studies: pregabalin (4 participants), placebo (4 participants), gabapentin (2 participants), and amitriptyline (1 participant) (very low-quality evidence).Serious adverse events were reported in both studies. One study reported only one serious adverse event (cholelithiasis and major depression resulting in hospitalisation in the pregabalin group) and the other study reported no serious adverse events (very low-quality evidence).There were few or no data for our remaining secondary outcomes (very low-quality evidence).We downgraded the evidence by three levels to very low due to too few data and the fact that the number of events was too small to be meaningful.

AUTHORS' CONCLUSIONS

This review identified only two small studies, with insufficient data for analysis.As we could undertake no meta-analysis, we were unable to comment about efficacy or harm from the use of antiepileptic drugs to treat chronic non-cancer pain in children and adolescents. Similarly, we could not comment on our remaining secondary outcomes: Carer Global Impression of Change; requirement for rescue analgesia; sleep duration and quality; acceptability of treatment; physical functioning; and quality of life.We know from adult randomised controlled trials that some antiepileptics, such as gabapentin and pregabalin, can be effective in certain chronic pain conditions.We found no evidence to support or refute the use of antiepileptic drugs to treat chronic non-cancer pain in children and adolescents.

Spatiotemporal changes of optical signals in the somatosensory cortex of neuropathic rats after electroacupuncture stimulation

Background

Peripheral nerve injury causes physiological changes in primary afferent neurons. Neuropathic pain associated with peripheral nerve injuries may reflect changes in the excitability of the nervous system, including the spinothalamic tract. Current alternative medical research indicates that acupuncture stimulation has analgesic effects in various pain symptoms. However, activation changes in the somatosensory cortex of the brain by acupuncture stimulation remain poorly understood. The present study was conducted to monitor the changes in cortical excitability, using optical imaging with voltage-sensitive dye (VSD) in neuropathic rats after electroacupuncture (EA) stimulation.

Methods

Male Sprague–Dawley rats were divided into three groups: control (intact), sham injury, and neuropathic pain rats. Under pentobarbital anesthesia, rats were subjected to nerve injury with tight ligation and incision of the tibial and sural nerves in the left hind paw. For optical imaging, the rats were re-anesthetized with urethane, and followed by craniotomy. The exposed primary somatosensory cortex (S1) was stained with VSD for one hour. Optical signals were recorded from the S1 cortex, before and after EA stimulation on Zusanli (ST36) and Yinlingquan (SP9).

Results

After peripheral stimulation, control and sham injury rats did not show significant signal changes in the S1 cortex. However, inflamed and amplified neural activities were observed in the S1 cortex of nerve-injured rats. Furthermore, the optical signals and region of activation in the S1 cortex were reduced substantially after EA stimulation, and recovered in a time-dependent manner. The peak fluorescence intensity was significantly reduced until 90 min after EA stimulation (Pre-EA: 0.25 ± 0.04 and Post-EA 0 min: 0.01 ± 0.01), and maximum activated area was also significantly attenuated until 60 min after EA stimulation (Pre-EA: 37.2 ± 1.79 and Post-EA 0 min: 0.01 ± 0.10).

Conclusion

Our results indicate that EA stimulation has inhibitory effects on excitatory neuronal signaling in the S1 cortex, caused by noxious stimulation in neuropathic pain. These findings suggest that EA stimulation warrants further study as a potential adjuvant modulation of neuropathic pain.

Intractable Epistaxis Associated with Topiramate Administration

Objective:

To report a case of a patient who experienced serious, intractable epistaxis warranting emergency department (ED) visits and hospital admission after initiation of topiramate therapy.

Case Summary:

A 61-year-old woman with significant cardiovascular disease was started on topiramate 25 mg daily for lower extremity neuropathy. After 7 days of treatment, she began to experience severe, intractable epistaxis that lasted 8 days, warranting an ED visit. The epistaxis resolved 1 week after topiramate discontinuation. Topiramate was restarted 3 months later, and the patient again developed intractable epistaxis. After 2 days of epistaxis, she returned to the ED with significant anginal pain and was admitted to the hospital, where she received 2 units of packed red blood cells. One week after stopping topiramate, the epistaxis stopped. At the time of writing, she had exhibited no epistaxis for 6 months. According to the Naranjo probability scale, topiramate was the probable cause of epistaxis.

Discussion:

Topiramate is a neuromodulatory compound approved for management of migraines, as well as partial and generalized tonic–clonic seizures. Over the past decade, its use has expanded to include many other neuropathic conditions. Currently, epistaxis has been reported in only 1–4% of patients receiving topiramate in clinical trials; however, these data were derived from a young study population. Like topiramate, calcium-channel blockers (CCBs) modulate voltage-gated L type calcium ion channels. These specific channels are located on vascular smooth muscle and non-contractile tissues such as platelets. Due to their possible antiplatelet effects, CCBs have been associated with an increased risk of hemorrhage, epistaxis, and prolonged bleeding time. The same may hold true for topiramate.

Conclusions:

Topiramate, particularly in combination with antiplatelet medications, may be associated with severe, intractable epistaxis. Intractable epistaxis should be added to the list of potentially serious adverse reactions that are monitored when topiramate is administered.

Potential drug therapies for the treatment of fibromyalgia

INTRODUCTION

Fibromyalgia (FM) is a common, complex chronic widespread pain condition is characterized by fatigue, sleep disturbance and cognitive dysfunction. Treatment of FM is difficult, requiring both pharmacological and non-pharmacological approaches, with an empiric approach to drug therapy focused toward individual symptoms, particularly pain. The effectiveness of current medications is limited with many patients discontinuing use.

AREAS COVERED

A systemic database search has identified 26 molecular entities as potential emerging drug therapies. Advances in the understanding of the pathophysiology of FM provides clues to targets for new medications. Investigation of bioamine modulation and α2δ ligands and novel targets such as dopamine receptors, NMDA receptors, cannabinoid receptors, melatonin receptors and potassium channels has identified potential drug therapies.

EXPERT OPINION

Modest improvement of health status in patients with FM has been observed with drugs targeting a diverse range of molecular mechanisms. No single drug, however, offered substantial efficacy against all the symptoms characteristic of FM. Identification of new and improved therapies for FM needs to address the heterogeneity of the condition, which suggests existence of patient subgroups, the relationship of central and peripheral aspects of the pathophysiology and a requirement of combination therapy with drugs targeting multiple molecular mechanisms.

Improvement in chronic low back pain in an obese patient with topiramate use

The objective of this study was to demonstrate efficacy, benefit, and potential use of topiramate in treating obese patients with chronic low back pain. This is a case report from an outpatient academic pain multidisciplinary clinical center. The patient was a 30-year-old morbidly obese (body mass index [BMI]: 61.4 kg/m(2)) female suffering from chronic low back pain. With a known association between obesity and chronic low back pain, and a possible role of topiramate in treating both simultaneously, the patient was started on a therapeutic trial of topiramate. Over a period of a 12-week topiramate therapy, the patient experienced clinically meaningful and significant weight loss as well as improvement in her chronic low back pain and functionality. With more substantial evidence, pain physicians may start considering using topiramate in the multimodal management of obesity-related chronic low back pain based on their thoughtful consideration of the drug's efficacy and side effects and the patient's comorbidities and preferences.

Inhibition of carbonic anhydrase augments GABAA receptor-mediated analgesia via a spinal mechanism of action

Peripheral nerve injury (PNI) negatively influences spinal gamma-aminobutyric acid (GABA)ergic networks via a reduction in the neuron-specific potassium-chloride (K(+)-Cl(-)) cotransporter (KCC2). This process has been linked to the emergence of neuropathic allodynia. In vivo pharmacologic and modeling studies show that a loss of KCC2 function results in a decrease in the efficacy of GABAA-mediated spinal inhibition. One potential strategy to mitigate this effect entails inhibition of carbonic anhydrase activity to reduce HCO3(-)-dependent depolarization via GABAA receptors when KCC2 function is compromised. We have tested this hypothesis here. Our results show that, similarly to when KCC2 is pharmacologically blocked, PNI causes a loss of analgesic effect for neurosteroid GABAA allosteric modulators at maximally effective doses in naïve mice in the tail-flick test. Remarkably, inhibition of carbonic anhydrase activity with intrathecal acetazolamide rapidly restores an analgesic effect for these compounds, suggesting an important role of carbonic anhydrase activity in regulating GABAA-mediated analgesia after PNI. Moreover, spinal acetazolamide administration leads to a profound reduction in the mouse formalin pain test, indicating that spinal carbonic anhydrase inhibition produces analgesia when primary afferent activity is driven by chemical mediators. Finally, we demonstrate that systemic administration of acetazolamide to rats with PNI produces an antiallodynic effect by itself and an enhancement of the peak analgesic effect with a change in the shape of the dose-response curve of the α1-sparing benzodiazepine L-838,417. Thus, carbonic anhydrase inhibition mitigates the negative effects of loss of KCC2 function after nerve injury in multiple species and through multiple administration routes resulting in an enhancement of analgesic effects for several GABAA allosteric modulators. We suggest that carbonic anhydrase inhibitors, many of which are clinically available, might be advantageously employed for the treatment of pathologic pain states.

PERSPECTIVE

Using behavioral pharmacology techniques, we show that spinal GABAA-mediated analgesia can be augmented, especially following nerve injury, via inhibition of carbonic anhydrases. Carbonic anhydrase inhibition alone also produces analgesia, suggesting these enzymes might be targeted for the treatment of pain.

Antiepileptic drugs for neuropathic pain and fibromyalgia - an overview of Cochrane reviews

BACKGROUND

Antiepileptic drugs have been used for treating different types of neuropathic pain, and sometimes fibromyalgia. Our understanding of quality standards in chronic pain trials has improved to include new sources of potential bias. Individual Cochrane reviews using these new standards have assessed individual antiepileptic drugs. An early review from this group, originally published in 1998, was titled 'Anticonvulsants for acute and chronic pain'. This overview now covers the neuropathic pain aspect of that original review, which was withdrawn in 2009.

OBJECTIVES

To provide an overview of the relative analgesic efficacy of antiepileptic drugs that have been compared with placebo in neuropathic pain and fibromyalgia, and to report on adverse events associated with their use.

METHODS

We included reviews published in theCochrane Database of Systematic Reviews up to August 2013 (Issue 7). We extracted information from each review on measures of efficacy and harm, and methodological details concerning the number of participants, the duration of studies, and the imputation methods used, in order to judge potential biases in available data.We analysed efficacy data for each painful condition in three tiers, according to outcome and freedom from known sources of bias. The first tier met current best standards - at least 50% pain intensity reduction over baseline (or its equivalent), without the use of last observation carried forward (LOCF) for dropouts, an intention-to-treat (ITT) analysis, in parallel group studies with at least 200 participants lasting eight weeks or more. The second tier used data from at least 200 participants where one or more of the above conditions were not met. The third tier of evidence related to data from fewer than 200 participants, or with several important methodological problems that limited interpretation.

MAIN RESULTS

No studies reported top tier results.For gabapentin and pregabalin only we found reasonably good second tier evidence for efficacy in painful diabetic neuropathy and postherpetic neuralgia. In addition, for pregabalin, we found evidence of efficacy in central neuropathic pain and fibromyalgia. Point estimates of numbers needed to treat for an additional beneficial effect (NNTs) were in the range of 4 to 10 for the important outcome of pain intensity reduction over baseline of 50% or more.For other antiepileptic drugs there was no evidence (clonazepam, phenytoin), so little evidence that no sensible judgement could be made about efficacy (valproic acid), low quality evidence likely to be subject to a number of biases overestimating efficacy (carbamazepine), or reasonable quality evidence indicating little or no effect (lamotrigine, oxcarbazepine, topiramate). Lacosamide recorded such a trivial statistical superiority over placebo that it was unreliable to conclude that it had any efficacy where there was possible substantial bias.Any benefits of treatment came with a high risk of adverse events and withdrawal because of adverse events, but serious adverse events were not significantly raised, except with oxcarbazepine.

AUTHORS' CONCLUSIONS

Clinical trial evidence supported the use of only gabapentin and pregabalin in some neuropathic pain conditions (painful diabetic neuropathy, postherpetic neuralgia, and central neuropathic pain) and fibromyalgia. Only a minority of people achieved acceptably good pain relief with either drug, but it is known that quality of life and function improved markedly with the outcome of at least 50% pain intensity reduction. For other antiepileptic drugs there was no evidence, insufficient evidence, or evidence of a lack of effect; this included carbamazepine. Evidence from clinical practice and experience is that some patients can achieve good results with antiepileptics other than gabapentin or pregabalin.There is no firm evidence to answer the important pragmatic questions about which patients should have which drug, and in which order the drugs should be used. There is a clinical effectiveness research agenda to provide evidence about strategies rather than interventions, to produce the overall best results in a population, in the shortest time, and at the lowest cost to healthcare providers.

Topiramate for neuropathic pain and fibromyalgia in adults

BACKGROUND

Topiramate is an antiepileptic drug with multiple possible mechanisms of action. Antiepileptic drugs are widely used to treat chronic neuropathic pain (pain due to nerve damage) and fibromyalgia, and many guidelines recommend them.

OBJECTIVES

To assess the analgesic efficacy and associated adverse events of topiramate for chronic neuropathic pain and fibromyalgia in adults (aged 18 years and above).

SEARCH METHODS

On 8 May 2013, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, and EMBASE. We reviewed the bibliographies of all randomised trials identified and review articles, and also searched two clinical trial databases, ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform, to identify additional published or unpublished data.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) with double-blind assessment of participant outcomes following two weeks of treatment or longer (though the emphasis of the review was on studies of eight weeks or longer) that used a placebo or active comparator.

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 where studies reported the outcome of at least 50% pain reduction from baseline, lasted at least eight weeks, had a parallel group design, included 200 or more participants in the comparison, and reported an intention-to-treat analysis. First tier studies did not use last-observation-carried-forward (LOCF) or other imputation methods for dropouts. The second tier used data that failed to meet this standard; second tier results were therefore subject to potential bias.

MAIN RESULTS

We included four studies with 1684 participants. Three parallel-group placebo comparisons were in painful diabetic neuropathy (1643 participants), and one cross-over study with diphenhydramine as an active placebo (41 participants) was in lumbar radiculopathy. Doses of topiramate were titrated up to 200 mg/day or 400 mg/day. All studies had one or more sources of potential major bias, as they either used LOCF imputation or were of small size.No study provided first tier evidence for an efficacy outcome. There was no convincing evidence for efficacy of topiramate at 200 to 400 mg/day over placebo.Eighty-two per cent of participants taking topiramate 200 to 400 mg/day experienced at least one adverse event, as did 71% with placebo, and the number needed to treat for an additional harmful effect (NNTH) was 8.6 (95% confidence interval (CI) 4.9 to 35). There was no difference in serious adverse events recorded (6.6% versus 7.5%). Adverse event withdrawals with 400 mg daily were much more common with topiramate (27%) than with placebo (8%), with an NNTH of 5.4 (95% CI 4.3 to 7.1). Lack of efficacy withdrawal was less frequent with topiramate (12%) than placebo (18%). Weight loss was a common event in most studies. No deaths attributable to treatment were reported.

AUTHORS' CONCLUSIONS

Topiramate is without evidence of efficacy in diabetic neuropathic pain, the only neuropathic condition in which it has been adequately tested. The data we have includes the likelihood of major bias due to LOCF imputation, where adverse event withdrawals are much higher with active treatment than placebo control. Despite the strong potential for bias, no difference in efficacy between topiramate and placebo was apparent.

Neurological perspectives on voltage-gated sodium channels

The activity of voltage-gated sodium channels has long been linked to disorders of neuronal excitability such as epilepsy and chronic pain. Recent genetic studies have now expanded the role of sodium channels in health and disease, to include autism, migraine, multiple sclerosis, cancer as well as muscle and immune system disorders. Transgenic mouse models have proved useful in understanding the physiological role of individual sodium channels, and there has been significant progress in the development of subtype selective inhibitors of sodium channels. This review will outline the functions and roles of specific sodium channels in electrical signalling and disease, focusing on neurological aspects. We also discuss recent advances in the development of selective sodium channel inhibitors.

Weight-reducing side effects of the antiepileptic agents topiramate and zonisamide

Drug-induced weight alteration can be a serious side effect that applies to several therapeutic agents and must be referred to in the respective approved labeling texts. The side effect may become health threatening in case of significant weight change in either direction. Several antiepileptic drugs (AEDs) are associated with weight gain such as gabapentin, pregabalin, valproic acid, and vigabatrin and to some extent carbamazepine. Others are weight neutral such as lamotrigine, levetiracetam, and phenytoin or associated with slight weight loss as, e.g., felbamate. The focus of this chapter is on the two AEDs causing strong weight loss: topiramate and zonisamide. For both drugs, several molecular mechanisms of actions are published. We provide a review of these potential mechanisms, some of which are based on in vivo studies in animal models for obesity, and of clinical studies exploring these two drugs as single entities or in combinations with other agents.

The mechanisms of antihyperalgesic effect of topiramate in a rat model of inflammatory hyperalgesia

Recent studies have shown that topiramate, a structurally novel anticonvulsant, exerts antinociceptive activity in animal models of neuropathic, acute somatic, and visceral pain. This study was aimed to examine: (i) the effects of systemically and locally peripherally administered topiramate in the rat inflammatory pain model and (ii) the potential role and site(s) of gamma-aminobutyric acid (GABA), opioid, and adrenergic receptors in topiramate's antihyperalgesia. Rats received intraplantar (i.pl.) injections of the pro-inflammatory compound carrageenan. A paw pressure test was used to determine: (i) the effect of systemic and local peripheral topiramate on carrageenan-induced hyperalgesia and (ii) the effects of systemic and local peripheral bicuculline (selective GABAA receptor antagonist), naloxone (nonselective opioid receptor antagonist), and yohimbine (selective α2-adrenergic receptor antagonist) on topiramate-induced antihyperalgesia. Systemic topiramate (40-160 mg/kg; p.o.) produced a significant dose-dependent reduction in the paw inflammatory hyperalgesia induced by carrageenan. The antihyperalgesic effect of systemic topiramate was significantly decreased by systemic bicuculline (0.5-1 mg/kg; i.p.), naloxone (2-5 mg/kg; i.p.), and yohimbine (1-3 mg/kg; i.p.). Local peripheral topiramate (0.03-0.34 mg/paw; i.pl.) also produced significant dose-dependent antihyperalgesia, which was significantly depressed by local peripheral yohimbine (0.05-0.2 mg/paw; i.pl.) but not by local peripheral bicuculline (0.15 mg/paw; i.pl.) or naloxone (0.1 mg/paw; i.pl.). The results suggest that topiramate produces systemic and local peripheral antihyperalgesia in an inflammatory pain model, which is, at least partially, mediated by central GABAA and opioid receptors and by peripheral and most probably central α2-adrenergic receptors. These findings contribute to better understanding of topiramate's action in pain states involving inflammation.

Quality of life and objective measures of diabetic neuropathy in a prospective placebo-controlled trial of ruboxistaurin and topiramate

BACKGROUND

The Norfolk Quality of Life Questionnaire-Diabetic Neuropathy (Norfolk QOL-DN) is a validated comprehensive questionnaire designed to capture the entire spectrum of DN related to large fiber, small fiber, and autonomic neuropathy not captured in existing instruments. We aimed to determine if the Norfolk QOL-DN could be used to capture changes in QOL that correlate with nerve fiber-specific objective measures in a placebo-controlled trial of two agents that affect different nerve fibers.

METHODS

Sixty patients with DN were allocated to treatment on ruboxistaurin (RBX) (n = 18), topiramate (TPX) (n = 18), or placebo (n = 18). QOL-DN was administered and objective measures of nerve function were performed at entry and end of the study period.

RESULTS

Total QOL scores improved significantly in the active treatment groups (RBX -9.56 ± 4.13; TPX -12.22 ± 2.76) but not in placebo (-5.56 ± 3.49). There were differences in nerve function improvement between treatments. Neurological symptom scores (NSS) improved with TPX from 5.5 (2.3) to 4.3 (0.65) (p = .007), sensory scores improved with TPX from 15.5 (1.79) to 8.3 (1.19) (p < .001), motor scores did not change, and sensory and motor impairment scores improved with TPX from 18.8 (2.15) to 12.1 (1.71) (p = .003). Total neuropathy scores (TNS) improved with TPX from 24.35 (2.61) to 16.35 (2.02) (p = .001). Neuropathy total symptom score-6 (NTSS-6) changes were significant for both treatments: RBX 4.38 (0.75) to 1.49 (0.38) (p < .001) and TPX 7.57 (1.3) to 4.26 (0.95) (p = .036). Changes in QOL-DN large fiber subscores correlated (Spearman's rank) significantly with changes in NTSS-6 (r = 0.55; p < .0001), NSS (r = 0.31; p < .04), neuropathy impairment score (NIS) (r = 0.35; p < .02), and TNS (r = 0.48; p < .0006). Changes in QOL-DN small fiber subscores correlated significantly with changes in NTSS-6 total scores (r = 0.40; p < .005) and intraepidermal nerve fiber density (IENFD) (r = -0.29; p < .05).

CONCLUSION

Ruboxistaurin produced significant improvement in large fiber measures while TPX produced significant changes in small fiber measures. The Norfolk QOL-DN tool differentiated between these changes captured in the fiber-specific domains. Correlations were found between objective measures of neuropathy and total QOL, but those with nerve fiber domain scores were modest and reinforce the need to quantify QOL as an endpoint in neuropathy independent of other measures.

Central neuropathic pain: an unusual case of painful ejaculation responding to topiramate

INTRODUCTION

Painful ejaculation (PE) is an uncommon condition and it is usually associated with prostatitis, chronic pelvic pain syndrome, benign prostatic hyperplasia, ejaculatory duct obstruction, radical prostatectomy, and prostate radiation. Topiramate (TPM) is a new antiepileptic drug with recognized efficacy in neuropathic pain.

AIM

The study is aimed to evaluate TPM efficacy in ejaculation pain.

METHODS

Following a spinal cord injury, a 53-year-old man was referred to our institute for persistent PE. Neurological examination showed mild hypoesthesia of the genital area. Urogenital examination, neurophysiological tools, and computed tomography of the dorso-lumbar spine were normal.

MAIN OUTCOME MEASURES

The main outcome measure was the visual analogue scale.

RESULTS

Since pain was refractory to conventional neuropathic pharmacological therapies, TPM was introduced up to 150 mg daily with a dramatic improvement of PE.

CONCLUSIONS

TPM may be considered as a valid therapeutic option for the treatment of PE.

Acetazolamide and midazolam act synergistically to inhibit neuropathic pain

Treatment of neuropathic pain is a major clinical challenge that has been met with minimal success. After peripheral nerve injury, a decrease in the expression of the K-Cl cotransporter KCC2, a major neuronal Cl(-) extruder, leads to pathologic alterations in GABA(A) and glycine receptor function in the spinal cord. The down-regulation of KCC2 is expected to cause a reduction in Cl(-) extrusion capacity in dorsal horn neurons, which, together with the depolarizing efflux of HCO(3)(-) anions via GABA(A) channels, would result in a decrease in the efficacy of GABA(A)-mediated inhibition. Carbonic anhydrases (CA) facilitate intracellular HCO(3)(-) generation and hence, we hypothesized that inhibition of CAs would enhance the efficacy of GABAergic inhibition in the context of neuropathic pain. Despite the decrease in KCC2 expression, spinal administration of benzodiazepines has been shown to be anti-allodynic in neuropathic conditions. Thus, we also hypothesized that spinal inhibition of CAs might enhance the anti-allodynic effects of spinally administered benzodiazepines. Here, we show that inhibition of spinal CA activity with acetazolamide (ACT) reduces neuropathic allodynia. Moreover, we demonstrate that spinal co-administration of ACT and midazolam (MZL) act synergistically to reduce neuropathic allodynia after peripheral nerve injury. These findings indicate that the combined use of CA inhibitors and benzodiazepines may be effective in the clinical management of neuropathic pain in humans.

Targeting voltage-gated calcium channels for neuropathic pain management

Voltage-gated calcium channels (VGCC) play obligatory roles in diverse physiological functions. Pathological conditions leading to changes in their biophysical properties and expression levels may cause malfunctions of VGCC-mediated activities, resulting in disease states. It is believed that changes in VGCC properties under pain-inducing conditions may play a causal role in the development of chronic pain, including nerve injury-induced pain or neuropathic pain. For the past several decades, preclinical and clinical research in developing VGCC blockers or modulators for chronic pain management has been fruitful, leading to some U.S. Food and Drug Administration-approved drugs currently available for chronic pain management. However, their efficacy in pain relief is limited in some patients, and their long-term use is limited by their side-effect profiles. Certainly, there is room for improvement in developing more subtype-specific VGCC blockers or modulators for chronic pain conditions. In this review, we summarized the most recent preclinical and clinical studies related to chronic pain medications acting on the VGCC. We also included clinical trials aiming to expand the application of approved VGCC drugs to different pain states derived from various pathological conditions, as well as drug combination therapies trying to improve the efficacies and side-effect profiles of current pain medications.

Paroxysmal hemicrania responding to topiramate

Chronic paroxysmal hemicrania (CPH) is a rare primary headache syndrome, which is classified along with cluster headache and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) as a trigeminal autonomic cephalalgia. CPH is exquisitely responsive to indomethacin, so much so that the response is one of the current diagnostic criteria. The case of a patient with CPH, who had marked epigastric symptoms with indomethacin treatment and responded well to topiramate 150 mg daily, is reported. Cessation of topiramate caused return of episodes, and the response has persisted for 2 years. Topiramate may be a treatment option in CPH.

Successful use of topiramate in a patient with severe postherpetic neuralgia

OBJECTIVE

To describe the case of a patient with postherpetic neuralgia (PHN) who had a marked response to topiramate despite failure of several previous therapies.

CASE SUMMARY

A 79-year-old white male with multiple medical comorbidities developed severe trigeminal territory PHN requiring treatment with opiates to maintain adequate pain relief. Topiramate was initiated after the patient failed treatment with 4 other antiepileptic medications due to various adverse events. After 3 months of topiramate therapy, with dosages up to 50 mg twice daily, PHN pain had decreased to the point that the patient was able to discontinue the use of opiates entirely. At time of writing, he continued to be maintained on topiramate 50 mg twice daily with good pain relief and no reported adverse effects.

DISCUSSION

Topiramate exhibits a number of actions that may contribute to the relief of neuropathic pain, including modulation of voltage-gated sodium and calcium channels, potentiation of gamma-aminobutyric acid inhibition, and blockade of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/kainite glutamate receptors. Current evidence-based recommendations consider topiramate to be a third-line agent for the treatment of neuropathic pain based on studies of its use in painful diabetic neuropathy and chronic lumbar radicular pain. A comprehensive search of MEDLINE (1950-August 2008) using the terms postherpetic neuralgia, neuralgia, and topiramate revealed only one previously published case report evaluating the use of topiramate specifically for treatment of PHN.

CONCLUSIONS

While it is impossible to determine whether pain relief in this case was due to treatment with topiramate as opposed to spontaneous resolution of pain over time, this additional case report suggests that topiramate may be a useful treatment option for patients with PHN who have not responded to or are intolerant of other interventions. Further studies are needed to determine whether topiramate should receive a stronger recommendation for the treatment of PHN.

Diabetic neuropathy: new strategies for treatment

Current therapeutic possibilities can be divided into two groups: the pathogenetically oriented and the symptomatic therapy. One of the most important component of etiology-based treatment is the stabilization of glycemic control. Based on efficacy and safety data benfotiamine and alpha-lipoic acid should be considered as first choices among pathogenetically oriented treatments of diabetic neuropathy. Promising data were published about the aldose reductase inhibitor ranirestat. The symptomatic effect of antiepileptic drugs in diabetic painful neuropathy (DPN) is originated from several possible pharmacological properties. Pregabalin and gabapentin have the highest efficacy and the lowest frequency of adverse events among these drugs. Antidepressants also extensively used for symptomatic treatment in DPN. In the last years several studies were published about the benefial effect of duloxetine. Most likely combination therapy will be frequently applied in the future for the treatment of DPN, the optimal choice could be to combine pathogenetically oriented and symptomatic treatment.

Trigeminal Autonomic Cephalalgias: Current and Future Treatments

The trigeminal autonomic cephalgias include cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT). The evidence for the current treatment options for each of these syndromes is considered, including oxygen, sumatriptan, and verapamil in cluster headache, indomethacin in paroxysmal hemicrania, and intravenous lidocaine and lamotrigine in SUNCT. Some treatments such as topiramate have an effect in all of these, as well as in migraine and other pain syndromes. The involvement of the hypothalamus in functional imaging studies implies that this may be a substrate for targeting treatment options in the future.

Painful posttraumatic trigeminal neuropathy: a case report of relief with topiramate

A case of chronic neuropathic pain in the infraorbital region following an untreated displaced zygomatic fracture is presented. The case responded favorably to topiramate and sensory testing revealed signs of nerve damage that remained unchanged over the follow-up period (six months) parallel to an analgesic effect. The clinical pharmacology of topiramate, which is reviewed, includes enhanced neuronal stability and neuroprotection, making it a possible candidate in the treatment of painful orofacial neuropathies.

Effects of topiramate on the prepulse inhibition of the acoustic startle in rats

The anticonvulsant topiramate (TPM) has been recently proposed as a novel adjuvant therapy for bipolar disorder and schizophrenia, yet its efficacy remains controversial. As both disorders are characterized by gating deficits, we tested the effects of TPM on the behavioral paradigm of prepulse inhibition (PPI) of the acoustic startle response, a validated animal model of sensorimotor gating. TPM (10, 18, 32, 58, 100 mg/kg, intraperitoneal, i.p.) enhanced PPI in rats in a dose-dependent fashion, prevented the PPI reduction mediated by the dopaminergic agonist apomorphine (0.25 mg/kg, subcutaneous, s.c.) and potentiated the effects of the antipsychotic drugs haloperidol (0.05, 0.1 mg/kg, i.p.) and clozapine (2.5, 5 mg/kg, i.p.). Conversely, TPM elicited no significant effect on the PPI disruption mediated by the NMDA receptor antagonist dizocilpine (0.05, 0.1 mg/kg, s.c.) and surprisingly antagonized the attenuation of dizocilpine-induced PPI disruption mediated by clozapine (5 mg/kg, i.p.). Our results suggest that TPM may exert diverse actions on the neural substrates of sensorimotor gating. While the pharmacological mechanisms of such effects are still elusive, our findings might contribute to shed light on some controversies on the therapeutic action of TPM, and point to this drug as a putative novel adjuvant therapy for some clusters of gating disturbances.

Anti-convulsants and anti-depressants

Damage to a nerve should only lead to sensory loss. While this is common, the incidence of spontaneous pain, allodynia and hyperalgesia indicate marked changes in the nervous system that are possible compensations for the loss of normal function that arises from the sensory loss. Neuropathic pain arises from changes in the damaged nerve which then alter function in the spinal cord and the brain and lead to plasticity in areas adjacent to those directly influenced by the neuropathy. The peripheral changes drive central compensations so that the mechanisms involved are multiple and located at a number of sites. Nerve damage increases the excitability of both the damaged and undamaged nerve fibres, neuromas and the cell bodies in the dorsal root ganglion. These peripheral changes are substrates for the ongoing pain and the efficacy of excitability blockers such as carbamazepine, lamotrigine and mexiletine, all anti-convulsants. A better understanding of ion channels at the sites of injury has shown important roles of particular sodium, potassium and calcium channels in the genesis of neuropathic pain. Within the spinal cord, increases in the activity of calcium channels and the receptors for glutamate, especially the N-methyl-D-aspartate (NMDA) receptor, trigger wind-up and central hyperexcitability. Increases in transmitter release, neuronal excitability and receptive field size result from the damage to the peripheral nerves. Ketamine and gabapentin/pregabalin, again with anti-convulsant activity, may interact with these mechanisms. Ketamine acts on central spinal mechanisms of excitability whereas gabapentin acts on a subunit of calcium channels that is responsible for the release of pain transmitters into the spinal cord. In addition to these spinal mechanisms of hyperexcitability, spinal cells participate in a spinal-supraspinal loop that involves parts of the brain involved in affective responses to pain but also engages descending excitatory and inhibitory systems that use the monoamines. These pathways become more active after nerve injury and are the site of action of anti-depressants. This chapter reviews the evidence and mechanisms of drugs, both anti-depressants and anti-convulsants, that are believed to be effective in pain control, with a major emphasis on the neuropathic state.

Use of antiepileptic drugs for nonepileptic conditions: psychiatric disorders and chronic pain

Antiepileptic drugs (AEDs) are commonly utilized for nonepileptic conditions, including various psychiatric disorders and pain syndromes. Evidence for their benefit in these nonepileptic conditions varies widely among different drugs, but there is, in general, a paucity of published multicenter randomized double-blind trials. Variable levels of evidence suggest that lamotrigine and the vagal nerve stimulator have antidepressant properties. Carbamazepine, valproate, lamotrigine, and oxcarbazepine appear to have mood stabilizing properties while gabapentin, pregabalin, and tiagabine have anxiolytic benefits. Barbiturates, topiramate, and possibly phenytoin may precipitate or exacerbate depression. Underlying depression and anxiety symptoms may be exacerbated by levetiracetam, while psychotic symptoms have rarely been reported with topiramate, levetiracetam, and zonisamide. Pregabalin, gabapentin, carbamazepine, and oxcarbazepine have been used to treat neuropathic pain such as postherpetic neuralgia, and diabetic polyneuropathy. Topiramate and divalproex sodium have utility in the prophylaxis or acute treatment of migraine. Further rigorous studies are needed to clarify the utility of AEDs in nonepileptic conditions.

Paroxysmal hemicrania responding to topiramate

Chronic paroxysmal hemicrania (CPH) is a rare primary headache syndrome, which is classified along with cluster headache and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) as a trigeminal autonomic cephalalgia. CPH is exquisitely responsive to indomethacin so much so that the response is one of the current diagnostic criteria. The case of a patient with CPH, who had marked epigastric symptoms with indomethacin treatment and responded well to topiramate 150 mg daily, is reported. Cessation of topiramate caused return of episodes, and the response has persisted for 2 years. Topiramate may be a treatment option in CPH.

The role of sodium channels in neuropathic pain

Our knowledge of the ion channels, receptors and signalling mechanisms involved in pain pathophysiology, and which specific channels play a role in subtypes of pain such as neuropathic and inflammatory pain, has expanded considerably in recent years. It is now clear that in the neuropathic state the expression of certain channels is modified, and that these changes underlie the plasticity of responses that occur to generate inappropriate pain signals from normally trivial inputs. Pain is modulated by a subset of the voltage-gated sodium channels, including Nav1.3, Nav1.7, Nav1.8 and Nav1.9. These isoforms display unique expression patterns within specific tissues, and are either up- or down-regulated upon injury to the nervous system. Here we describe our current understanding of the roles of sodium channels in pain and nociceptive information processing, with a particular emphasis on neuropathic pain and drugs useful for the treatment of neuropathic pain that act through mechanisms involving block of sodium channels. One of the future challenges in the development of novel sodium channel blockers is to design and synthesise isoform-selective channel inhibitors. This should provide substantial benefits over existing pain treatments.

Neuropathic agents and pain. New strategies

At present, the opioids, anti-epileptic, membrane stabilising and anti-depressant drugs are the mainstay of treatment for alleviating neuropathic pain. This article summarises data on some new medications of these classes and also other groups of medications in development. Recent data on the use of combination medications and its implications will also be discussed.

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

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

Uses of topiramate in the treatment of alcohol dependence

Alcohol dependence is a major cause of morbidity and mortality in the USA and throughout the world. Over the last 10 years there has been an intense interest in developing pharmacotherapies that address the neurochemistry of alcohol dependence. Using a novel pharmacological approach to treating alcohol dependence, topiramate (Topamax, Ortho-McNeil Pharmaceutical) has recently been shown to improve the drinking outcomes of alcohol-dependent individuals. This drug profile highlights the scientific concepts and clinical evidence in the development of topiramate for treating alcohol dependence.