Low-dose gabapentin combined with either lamotrigine or carbamazepine can be useful therapies for trigeminal neuralgia in multiple sclerosis

Considerations When Using Gabapentinoids to Treat Trigeminal Neuralgia: A Review

Despite the exemplary efficacy of voltage-gated sodium channel blockers as a first-line treatment of trigeminal neuralgia, the pharmacological management of this excruciating facial pain condition remains a major issue, as these first-line drugs produce intolerable side effects in a significant portion of patients. In addition, in patients with concomitant continuous pain, the efficacy of these drugs may drop, thus suggesting the opportunity to test the efficacy of different drug categories. The aim of this review is to provide current, evidence-based, knowledge about the use of gabapentin and other α2δ ligands in patients with trigeminal neuralgia. We searched for relevant papers within PubMed, EMBASE, the Cochrane Database of Systematic Reviews and the Clinical Trials database (ClinicalTrials.gov), considering publications up to April 2023. Two authors independently selected studies for inclusion and data extraction. The efficacy of α2δ ligands, gabapentin and pregabalin, has been assessed in seven controlled or open-label studies. Despite the low quality of evidence, the favorable tolerability profile and the possible action on concomitant continuous pain make this drug category of interest for future trials in trigeminal neuralgia.

Case Series: Synergistic Effect of Gabapentin and Adjuvant Pregabalin in Neuropathic Pain

Gabapentin and pregabalin both exert high affinity to the α2δ subunit of the voltage-gated calcium channels which inhibits excitatory neurotransmitter release. The synergistic mechanism was described in rats given combinations of gabapentin and pregabalin. In this case series, we described 2 cases which may illustrate the synergistic effect of gabapentin and pregabalin in treatment resistant neuropathic pain. Low dose pregabalin was added to therapeutic gabapentin to achieve appreciable pain reduction in one case and improved quality of life in another case. Further research with more enrollment and longer study duration may help elucidate the appropriate dosing and potential associated side effects.

Neurorehabilitation in Multiple Sclerosis-A Review of Present Approaches and Future Considerations

Multiple sclerosis is an increasingly prevalent disease, representing the leading cause of non-traumatic neurological disease in Europe and North America. The most common symptoms include gait deficits, balance and coordination impairments, fatigue, spasticity, dysphagia and an overactive bladder. Neurorehabilitation therapeutic approaches aim to alleviate symptoms and improve the quality of life through promoting positive immunological transformations and neuroplasticity. The purpose of this study is to evaluate the current treatments for the most debilitating symptoms in multiple sclerosis, identify areas for future improvement, and provide a reference guide for practitioners in the field. It analyzes the most cited procedures currently in use for the management of a number of symptoms affecting the majority of patients with multiple sclerosis, from different training routines to cognitive rehabilitation and therapies using physical agents, such as electrostimulation, hydrotherapy, cryotherapy and electromagnetic fields. Furthermore, it investigates the quality of evidence for the aforementioned therapies and the different tests applied in practice to assess their utility. Lastly, the study looks at potential future candidates for the treatment and evaluation of patients with multiple sclerosis and the supposed benefits they could bring in clinical settings.

Anti-inflammatory and Neuroprotective Agents in Clinical Trials for CNS Disease and Injury: Where Do We Go From Here?

Neurological disorders are major contributors to death and disability worldwide. The pathology of injuries and disease processes includes a cascade of events that often involve molecular and cellular components of the immune system and their interaction with cells and structures within the central nervous system. Because of this, there has been great interest in developing neuroprotective therapeutic approaches that target neuroinflammatory pathways. Several neuroprotective anti-inflammatory agents have been investigated in clinical trials for a variety of neurological diseases and injuries, but to date the results from the great majority of these trials has been disappointing. There nevertheless remains great interest in the development of neuroprotective strategies in this arena. With this in mind, the complement system is being increasingly discussed as an attractive therapeutic target for treating brain injury and neurodegenerative conditions, due to emerging data supporting a pivotal role for complement in promoting multiple downstream activities that promote neuroinflammation and degeneration. As we move forward in testing additional neuroprotective and immune-modulating agents, we believe it will be useful to review past trials and discuss potential factors that may have contributed to failure, which will assist with future agent selection and trial design, including for complement inhibitors. In this context, we also discuss inhibition of the complement system as a potential neuroprotective strategy for neuropathologies of the central nervous system.

Treatment Outcomes in Trigeminal Neuralgia-A Systematic Review of Domains, Dimensions and Measures

BACKGROUND

Trigeminal neuralgia (TN) is a painful disorder characterized by sudden electric shock-like pain. It is a rare condition for which multiple treatments are available, including medical and surgical. The best treatment option is yet to be defined, and this is related to the lack of definition in the treatment outcomes and outcome measures. The aim of this systematic review was to summarize all the outcomes and outcomes measures that have been published to date and highlight variability in their use.

METHODS

We have conducted a literature search using a wide range of databases (1946-2019 for medical and 2008-2019 for surgical treatment), for all intervention studies in TN. Four hundred and sixty-seven studies were selected for data extraction on TN classification, data collection method, intervention, and treatment outcomes mapped to the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT guidelines).

RESULTS

Most studies collected data on pain (n = 459) and side effects (n = 386) domains; however, very few collected data on the impact of treatment on physical (n = 46) and emotional functioning (n = 17) and on patient satisfaction (n = 35). There was high variability on outcome measures used for pain relief (n = 10), pain intensity (n = 9), and frequency of pain episodes (n = 3).

CONCLUSIONS

A clear definition of what are the important outcomes for patients with TN is essential. The choice of standardized outcome measures allowing for consistent reporting in TN treatment will allow for comparison of studies and facilitate treatment choice for patients and clinicians thus, improving health outcomes and reducing health care cost.

Trigeminal neuralgia secondary to multiple sclerosis: from the clinical picture to the treatment options

BACKGROUND

Trigeminal neuralgia is one of the most characteristic and difficult to treat neuropathic pain conditions in patients with multiple sclerosis. The present narrative review addresses the current evidence on diagnostic tests and treatment of trigeminal neuralgia secondary to multiple sclerosis.

METHODS

We searched for relevant papers within PubMed, EMBASE and the Cochrane Database of Systematic Reviews, taking into account publications up to December 2018.

RESULTS

Trigeminal neuralgia secondary to multiple sclerosis manifests with facial paroxysmal pain triggered by typical manoeuvres; neurophysiological investigations and MRI support the diagnosis, providing the definite evidence of trigeminal pathway damage. A dedicated MRI is required to identify pontine demyelinating plaques. In many patients with multiple sclerosis, neuroimaging and surgical evidence suggests that neurovascular compression might act in concert with the pontine plaque through a double-crush mechanism. Although no placebo-controlled trials have been conducted in these patients, according to expert opinion the first-line therapy for trigeminal neuralgia secondary to multiple sclerosis relies on sodium-channel blockers, i.e. carbamazepine and oxcarbazepine. The sedative and motor side effects of these drugs frequently warrant an early consideration for neurosurgery. Surgical procedures include Gasserian ganglion percutaneous techniques, gamma knife radiosurgery and microvascular decompression in the posterior fossa.

CONCLUSIONS

The relatively poor tolerability of the centrally-acting drugs carbamazepine and oxcarbazepine highlights the need to develop new selective and better-tolerated sodium-channel blockers. Prospective studies based on more advanced neuroimaging techniques should focus on how trigeminal anatomical abnormalities may be able to predict the efficacy of microvascular decompression.

Current and Innovative Pharmacological Options to Treat Typical and Atypical Trigeminal Neuralgia

Trigeminal neuralgia is a representative neuropathic facial pain condition, characterised by unilateral paroxysmal pain in the distribution territory of one or more divisions of the trigeminal nerve, triggered by innocuous stimuli. A subgroup of patients with trigeminal neuralgia [TN (previously defined as atypical TN)] also suffer from concomitant continuous pain, i.e. a background pain between the paroxysmal attacks. The aim of this review is to provide current, evidence-based, knowledge about the pharmacological treatment of typical and atypical TN, with a specific focus on drugs in development. We searched for relevant papers within PubMed, EMBASE, the Cochrane Database of Systematic Reviews and the Clinical Trials database (ClinicalTrials.gov), taking into account publications up to February 2018. Two authors independently selected studies for inclusions, data extraction, and bias assessment. Carbamazepine and oxcarbazepine are the first-choice drugs for paroxysmal pain. When sodium channel blockers cannot reach full dosage because of side effects, an add-on treatment with lamotrigine or baclofen should be considered. In patients with atypical TN, both gabapentin and antidepressants are expected to be efficacious and should be tried as an add-on to oxcarbazepine or carbamazepine. Although carbamazepine and oxcarbazepine are effective in virtually the totality of patients, they are responsible for side effects causing withdrawal from treatment in an important percentage of cases. A new, better tolerated, Nav1.7 selective state-dependent, sodium channel blocker (vixotrigine) is under development. Future trials testing the effect of combination therapy in patients with TN are needed, especially in patients with concomitant continuous pain and in TN secondary to multiple sclerosis.

A Systematic Review of the Management of Trigeminal Neuralgia in Patients with Multiple Sclerosis

BACKGROUND AND OBJECTIVE

Patients with trigeminal neuralgia (TN) and multiple sclerosis (MS) are often treated with medications or a surgical procedure. However, there is little evidence that such treatments result in 50% pain reduction and improvement in quality of life. The aim of this systematic review is to evaluate the clinical effectiveness of treatments in patients with MS and trigeminal neuralgia.

METHODS

We searched Medline, EMBASE, and the Cochrane Collaboration database from inception until October 2016. Two authors independently selected studies for inclusions, data extraction, and bias assessment.

RESULTS

All studies were of low quality using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. For medical management, 10 studies were included, of which one was a randomized controlled trial. Two studies were on the use of misopropol, unique to patients with MS. For surgical therapy, 26 studies with at least 10 patients and a minimum of 2 years follow-up were included. All types of surgical procedures are reported and the results are poorer for TN with MS, with 50% having a recurrence by 2 years. The main complication was sensory loss. Many patients had to undergo further procedures to become pain free and there were no agreed prognostic factors.

CONCLUSIONS

There was insufficient evidence to support any 1 medical therapy and so earlier surgery may be preferable. A patient with TN and MS has therefore to make a decision based on low-level evidence, beginning with standard drug therapy and then choosing a surgical procedure.

Pharmacological treatment of trigeminal neuralgia

INTRODUCTION

Unique among the different neuropathic pain conditions, trigeminal neuralgia frequently has an excellent response to some selected drugs, which, on the other hand, often entail disabling side effects. Physicians should be therefore acquainted with the management of these drugs and the few alternative options. Areas covered: This article, based on a systematic literature review, describes the pharmacological options, and indicates the future perspectives for treating trigeminal neuralgia. The article therefore provides current, evidence-based knowledge about the pharmacological treatment of trigeminal neuralgia, and suggests a practical approach to the various drugs, including starting dose, titration and side effects. Expert commentary: Carbamazepine and oxcarbazepine are the reference standard drugs for treating patients with trigeminal neuralgia. They are effective in most patients. The undesired effects however cause withdrawal from treatment or a dosage reduction to an insufficient level in many patients. Sodium channel blockers selective for the sodium channel 1.7 (Nav1.7) receptor, currently under development, might be an alternative, better-tolerated pharmacological option in the next future.

Trigeminal Neuralgia Commonly Precedes the Diagnosis of Multiple Sclerosis

BACKGROUND

Trigeminal neuralgia (TN) is a well-recognized cause of facial pain in the general population, and multiple sclerosis (MS) accounts for some of these cases. However, the prevalence of TN in MS is poorly understood. We investigated the prevalence of TN and how often TN is the initial presentation of MS in a large MS cohort.

METHODS

In 2009, we surveyed participants in the North America Research Committee on Multiple Sclerosis Registry regarding TN, including date of onset and pharmacologic and nonpharmacologic treatments used. We estimated the frequency of TN and the frequency with which TN preceded the diagnosis of MS. We compared the demographic and clinical characteristics of participants who reported TN with those of participants who did not using descriptive statistics and logistic regression.

RESULTS

Among 8590 eligible survey respondents, the prevalence of TN was 830 (9.7%). Of these respondents, 588 reported the year when TN was diagnosed. The diagnosis of TN preceded that of MS in 88 respondents (15.0%), and the mean ± SD age at diagnosis of TN was 45.3 ± 11.0 years. The odds of reporting TN were higher in women and those with greater disability and longer disease duration. Pharmacologic treatments were used by 88.3% of respondents; 9.7% underwent surgical interventions.

CONCLUSIONS

In MS, TN occurs frequently and precedes the diagnosis of MS in 15.0% of individuals. Given the frequency of TN in MS, further epidemiological studies and clinical trials to identify effective pharmacologic and nonpharmacologic therapies for TN in MS are warranted.

Efficacy and Safety of Gabapentin vs. Carbamazepine in the Treatment of Trigeminal Neuralgia: A Meta-Analysis

To evaluate the safety and efficacy of gabapentin in comparison with carbamazepine in the treatment of trigeminal neuralgia, a meta-analysis of randomized controlled trials was performed. Two reviewers independently selected studies, assessed study quality, and extracted data. Sixteen randomized controlled trials that included 1,331 patients were assessed. The meta-analysis showed that the total effective rate of gabapentin therapy group was similar with carbamazepine therapy group (OR = 1.600, 95% CI 1.185, 2.161, P = 0.002). While the effective rate of gabapentin therapy for 4 weeks was higher than that of carbamazepine therapy (OR = 1.495, 95% CI 1.061, 2.107, P = 0.022, heterogeneity: x² = 7.12, P = 0.625, I² = 0.0%), the life satisfaction improvement is also better in the gabapentin therapy group after a 4-week treatment (SMD = 0.966, 95% CI 0.583, 1.348, P < 0.001). Furthermore, our meta-analysis suggested that the adverse reaction rate of gabapentin therapy group was significantly lower than that of carbamazepine therapy group (OR = 0.312, 95% CI 0.240, 0.407, P < 0.001). In conclusion, present trials comparing gabapentin with carbamazepine are all poor in terms of methodological quality. Based on the available evidence, it is not possible to draw conclusions regarding the efficacy and side effects of gabapentin being superior to carbamazepine.

Botulinum neurotoxin type A in the treatment of classical Trigeminal Neuralgia (BoTN): study protocol for a randomized controlled trial

BACKGROUND

Trigeminal neuralgia is characterized by paroxysmal facial pain attacks. Adequate prophylactic drug therapy is often limited by the lack of efficacy and intolerance due to central nervous system side effects. Subcutaneous injections of botulinum toxin type A are a promising treatment option for patients with unsatisfactory response to drug therapy or neurosurgical intervention. Its effects are expected to last for at least 3 months, so it could be a potential long-term treatment. This is the study protocol of a prospective, placebo-controlled, double blind clinical trial investigating the add-on therapy of subcutaneous administration of botulinum toxin type A injections to standard treatment in therapy-refractory classical trigeminal neuralgia.

METHODS AND DESIGN

BoTN is a prospective, double blind, placebo-controlled trial with a randomized withdrawal design in which a single blind phase is followed by a double blind phase (see also Methods and design). Eligible patients with classical trigeminal neuralgia who are otherwise refractory to medical and neurosurgical treatment will receive subcutaneous injections of botulinum toxin type A into injection sites of the affected trigeminal branch. In the first phase all patients will receive botulinum toxin type A in a single blinded intervention. Twelve weeks later therapy responders will be allocated to the verum or placebo (saline) arm in a double blind, randomized manner. These injections will be performed at the same sites as the first injections. This trial will be conducted in a tertiary outpatient clinic specialized in the treatment of headache and facial pain. There will be three investigators performing the injections who are experienced in the treatment of headache and facial pain and trained in botulinum toxin type A injections.

DISCUSSION

BoTN is designed to assess the efficacy and safety of subcutaneous botulinum toxin type A injections in addition to standard prophylactic treatment in therapy-refractory trigeminal neuralgia.

TRIAL REGISTRATION NUMBER

EU Clinical Trials Register: EudraCT-No: 2014-001959-24 https://www.clinicaltrialsregister.eu/ctr-search/rest/download/trial/2014-001959-24/DE Date of trial registration 26 August 2014.

Trigeminal neuralgia (part II): Factors affecting early pharmacotherapeutic outcome

Aims

We conducted a cohort study to examine demographic and clinical features associated with the pharmacotherapeutic outcome in classical trigeminal neuralgia (CTN) patients.

Methods

Patients with a clinical profile indicating a diagnosis of CTN, as per the International Headache Society’s published classification, were enrolled prospectively. Demographic and pain-related characteristics were carefully collected. For the purposes of the study, patients with features such as autonomic signs and longer attack duration were included. All patients were then initiated on a standardised and accepted stepped pharmacotherapeutic protocol for the management of CTN. Initial pain scores and prospectively collected pain scores from pain diaries were used to assess the treatment outcome, with a ≥50% reduction considered significant.

Results

A total of 86 patients were seen, of whom five had an underlying disorder that could account for the pain. The study cohort therefore consisted of 81 patients, and based on attack duration these were divided into short (≤2 minutes, n = 61) and long (>2 minutes, n = 20) groups, for further analysis. The features of these patients and a discussion on the differential diagnosis have been presented in part 1 of this report. Employing an accepted stepped pharmacotherapeutic protocol for the management of CTN, significant improvement was more frequent in the short (74%) than in the long attack group (50%, p = 0.05). In the short attack group there were statistically significant associations between a poor treatment response and longer disease duration, the presence of autonomic signs and atypical pain descriptors for pain quality ( p < 0.05).

Conclusion

This report supports previous findings that prolonged disease duration and autonomic signs are negative prognostic indicators. The present study now adds long attack duration as a further negative prognostic sign.

A randomized placebo-controlled trial of duloxetine for central pain in multiple sclerosis

BACKGROUND

Pain is common in multiple sclerosis (MS). Duloxetine has a potential therapeutic role in treating MS-related pain.

METHODS

Thirty-eight MS patients were randomized 1:1 to receive duloxetine (n = 18) or matched placebo (n = 20). The dosing regimen was 30 mg daily for 1 week, then 60 mg daily for 5 weeks. The primary outcome measure was change in worst pain for week 6 relative to baseline recorded on a daily pain diary.

RESULTS

Of 38 randomized patients, 14 (78%) patients randomized to duloxetine and 18 (90%) randomized to placebo completed treatment per protocol. These participants had an average age of 55.5 years, 25% were male, and 66% had relapsing-remitting MS (RRMS). Baseline characteristics were similar. Discontinuations were due primarily to drug intolerance. Among those who completed treatment, worst pain at 6 weeks was reduced by 29% (±20%) for duloxetine versus 12% (±18%) for placebo (P = .016). Average daily pain at 6 weeks was reduced by 39% (±29%) in the duloxetine group compared to 10% (±18.8%) in the placebo group (P = .002). There were no significant changes (week 6 vs. baseline) or between-group differences for subject global impression, Beck Depression Inventory, 36-item Short Form Health Status Survey (SF-36), or sleep quality score.

CONCLUSIONS

Fewer patients could tolerate duloxetine compared to placebo. Among patients who completed 6 weeks of treatment, there were significant reductions in average and worst daily pain scores with duloxetine compared to placebo. This study suggests that duloxetine has a direct pain-relieving effect in MS.

A retrospective study of 72 cases diagnosed with idiopathic trigeminal neuralgia in indian populace

Context: Trigeminal neuralgia is as a chronic, debilitating condition, which can have a major impact on quality of life. There are few reports of trigeminal neuralgia in oriental populations. Objectives: To evaluate the retrospective data of the patients diagnosed with idiopathic trigeminal neuralgia and to understanding the disorder in the Indian populace. Methods: The retrospective data of 72 patients with typical idiopathic trigeminal neuralgia regarding age of onset, gender, site of involvement, clinical presentations and treatment received during three years of the follow up was collected and analyzed. Results: In the present retrospective study, the mean age was 54.9 years; female to male ratio was 2.13:1; rural to urban ratio 1.76:1 with 62.5% suffered trigeminal neuralgic pain on the right side. Carbamazepine was found to be highly effective in 60.8% of the cases on long-term basis with maintenance doses. Other treatment modalities were employed in more refractory cases including add-on of gabapentin, which relieved the symptoms for an additional duration of 13±3months. The neurolytic alcohol bloc was given in 30% of patients who stopped responding to combination of carbamazepine and gabapentin and relieved pain for a mean duration of 17.25±2.95 months. Twenty three percent of the patients (23%) required peripheral neurectomy. Conclusions: Carbamazepine was found to be highly effective in trigeminal neuralgia. Other treatment modality includes add-on of gabapentin, neurolytic alcohol blocs and peripheral surgical intervention in more refractory cases. Only limited cases needed further neurological consideration.

Key words:Trigeminal neuralgia, carbamazepine, gabapentin, alcohol bloc, peripheral neurectomy.

Update on neuropathic pain treatment: ion channel blockers and gabapentinoids

Neuropathic pain is a debilitating chronic pain condition, which remains difficult to treat. The current mainstays of treatment include physical therapy, interventional procedures and medications. Among medications, ion channel blockers and gabapentinoids are the 2 classes of drugs commonly used to treat neuropathic pain. It has been suggested that these medications may be useful to treat a variety of neuropathic pain conditions. This article provides several updates on the utility of both ion channel blockers and gabapentinoids for the treatment of neuropathic pain.

Multiple sclerosis-induced neuropathic pain: pharmacological management and pathophysiological insights from rodent EAE models

In patients with multiple sclerosis (MS), pain is a frequent and disabling symptom. The prevalence is in the range 29-86 % depending upon the assessment protocols utilised and the definition of pain applied. Neuropathic pain that develops secondary to demyelination, neuroinflammation and axonal damage in the central nervous system is the most distressing and difficult type of pain to treat. Although dysaesthetic extremity pain, L'hermitte's sign and trigeminal neuralgia are the most common neuropathic pain conditions reported by patients with MS, research directed at gaining insight into the complex mechanisms underpinning the pathobiology of MS-associated neuropathic pain is in its relative infancy. By contrast, there is a wealth of knowledge on the neurobiology of neuropathic pain induced by peripheral nerve injury. To date, the majority of research in the MS field has used rodent models of experimental autoimmune encephalomyelitis (EAE) as these models have many clinical and neuropathological features in common with those observed in patients with MS. However, it is only relatively recently that EAE-rodents have been utilised to investigate the mechanisms contributing to the development and maintenance of MS-associated central neuropathic pain. Importantly, EAE-rodent models exhibit pro-nociceptive behaviours predominantly in the lower extremities (tail and hindlimbs) as seen clinically in patients with MS-neuropathic pain. Herein, we review research to date on the pathophysiological mechanisms underpinning MS-associated neuropathic pain as well as the pharmacological management of this condition. We also identify knowledge gaps to guide future research in this important field.

Pharmacological treatment of pain in multiple sclerosis

Pain is a common symptom in multiple sclerosis (MS) and was recently estimated to be experienced by up to 75% of patients. Nociceptive and neuropathic pain in MS may be present concurrently and at different stages of the disease and may be associated with other symptoms. Evidence for treating pain in MS is limited. Many clinical features of pain are often unrecognized by clinicians and are difficult for patients to describe. Treatment is often based on anecdotal reports and clinical experience. We present a review of treatment options for pain in MS that should serve to update current knowledge, highlight shortcomings in clinical research and provide indications towards achieving evidence-based treatment of pain in MS.

Symptomatic treatment and management of multiple sclerosis

The range of symptoms which occur in multiple sclerosis (MS) can have disabling functional consequences for patients and lead to significant reductions in their quality of life. MS symptoms can also interact with each other, making their management challenging. Clinical trials aimed at identifying symptomatic therapies have generally been poorly designed and have tended to be underpowered. Therefore, the evidence base for the management of MS symptoms with pharmacologic therapies is not strong and tends to rely upon open-label studies, case reports, and clinical trials with small numbers of patients and poorly validated clinical outcome measures. Recently, there has been a growing interest in the management of MS symptoms with pharmacologic treatments, and better-designed, randomized, double-blind, controlled trials have been reported. This chapter will describe the evidence base predominantly behind the various pharmacologic approaches to the management of MS symptoms, which in most, if not all, cases, requires multidisciplinary input. Drugs routinely recommended for individual symptoms and new therapies, which are currently in the development pipeline, will be reviewed. More interventional therapies related to symptoms that are refractory to pharmacotherapy will also be discussed, where relevant.

Trigeminal and glossopharyngeal neuralgia

Trigeminal neuralgia and glossopharyngeal neuralgia are two causes of paroxysmal craniofacial pain. Either can be debilitating in affected individuals. This article reviews the epidemiology, pathogenesis, diagnosis, and treatment options for these disorders.

Combined carbamazepine and pregabalin therapy in a rat model of neuropathic pain

BACKGROUND

Carbamazepine and pregabalin have proven effects against neuropathic pain. Carbamazepine blocks voltage-dependent Na(+) channels, whereas pregabalin blocks voltage-dependent Ca(2+) channels. The authors hypothesized that the co-administration of these drugs would synergistically reduce neuropathic pain.

METHODS

Neuropathic pain was induced by L5 nerve ligation in Sprague-Dawley rats. To determine their ED(50) values, carbamazepine and pregabalin were orally administered at 0.3, 3, 10, or 30 mg kg(-1). The drugs were then co-administered at 0, 1/4×ED(50), 1/2×ED(50), 1.5×ED(50), and 2×ED(50) to determine the ED(50) and ED(75) values of the drugs in combination. Allodynia was determined using the von Frey hair test and dose-effect curves and isobolograms were used to investigate drug interactions. Levels of the acute reactive protein c-Fos in the dorsal horn were evaluated as an indicator of pathological nerve excitation.

RESULTS

At ED(50) levels, carbamazepine and pregabalin did not exhibit synergism, but doses higher than ED(75) were found to be synergistic. The combination index was 0.18 (strong synergy) and dose reductions were 35.7-fold for carbamazepine and 6.8-fold for pregabalin when co-administered when compared with a single administration at ED(75). The percentage allodynia relief was only 60% for carbamazepine and 80% for pregabalin by single administration, whereas their co-administration relieved allodynia by 100%. Furthermore, treatment decreased c-Fos expression in the dorsal horn, but expressional differences between animals treated with carbamazepine plus pregabalin were not significantly different from those treated with single drug.

CONCLUSIONS

Carbamazepine and pregabalin ameliorate neuropathic pain synergistically at higher doses.

Treating pain in multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an inflammatory, demyelinating, central nervous system disease that frequently causes pain.

AREAS COVERED

This article reviews the current literature and describes the therapeutic options for treating MS-related pain. The reader will be provided with current, evidence-based knowledge about the treatment of MS-related pain, and the review will take a practical approach to the various drugs for treating pain, including starting dose, titration and side effects.

EXPERT OPINION

Only cannabinoids have been assessed in randomized, controlled trials. Because of the concern regarding the risk of abuse and psychiatric adverse events, published guidelines as well as expert recommendations suggest using them as second-line therapy only. Hence, current treatment should be based on the general principles for treating peripheral neuropathic pain, taking into account drug-induced adverse effects.

Anti-epileptic drugs

Therapeutic Reviews aim to provide essential independent information for health professionals about drugs used in palliative and hospice care. Additional content is available on www.palliativedrugs.com. Country-specific books (Hospice and Palliative Care Formulary USA, and Palliative Care Formulary, British and Canadian editions) are also available and can be ordered from www.palliativedrugs.com. The series editors welcome feedback on the articles (hq@palliativedrugs.com).

Pharmacological versus microvascular decompression approaches for the treatment of trigeminal neuralgia: clinical outcomes and direct costs

In idiopathic trigeminal neuralgia (TN) the neuroimaging evaluation is usually normal, but in some cases a vascular compression of trigeminal nerve root is present. Although the latter condition may be referred to surgery, drug therapy is usually the first approach to control pain. This study compared the clinical outcome and direct costs of (1) a traditional treatment (carbamazepine [CBZ] in monotherapy [CBZ protocol]), (2) the association of gabapentin (GBP) and analgesic block of trigger-points with ropivacaine (ROP) (GBP+ROP protocol), and (3) a common TN surgery, microvascular decompression of the trigeminal nerve (MVD protocol). Sixty-two TN patients were randomly treated during 4 weeks (CBZ [n = 23] and GBP+ROP [n = 17] protocols) from cases of idiopathic TN, or selected for MVD surgery (n = 22) due to intractable pain. Direct medical cost estimates were determined by the price of drugs in 2008 and the hospital costs. Pain was evaluated using the Numerical Rating Scale (NRS) and number of pain crises; the Hospital Anxiety and Depression Scale, Sickness Impact Profile, and satisfaction with treatment and hospital team were evaluated. Assessments were performed at day 0 and 6 months after the beginning of treatment. All protocols showed a clinical improvement of pain control at month 6. The GBP+ROP protocol was the least expensive treatment, whereas surgery was the most expensive. With time, however, GBP+ROP tended to be the most and MVD the least expensive. No sequelae resulted in any patient after drug therapies, while after MDV surgery several patients showed important side effects. Data reinforce that, (1) TN patients should be carefully evaluated before choosing therapy for pain control, (2) different pharmacological approaches are available to initiate pain control at low costs, and (3) criteria for surgical interventions should be clearly defined due to important side effects, with the initial higher costs being strongly reduced with time.

WITHDRAWN: Gabapentin for acute and chronic pain

BACKGROUND

February 2009: The authors are aware of unpublished trial data for Gabapentin which could affect the results of this review. This information together with that from trials published since 2005, will be considered when this review is updated in 2009.Anticonvulsant drugs have been used in the management of pain since the 1960s. The clinical impression is that they are useful for chronic neuropathic pain, especially when the pain is lancinating or burning.

OBJECTIVES

To evaluate the analgesic effectiveness and adverse effects of gabapentin for pain management in clinical practice.

SEARCH STRATEGY

Randomised trials of gabapentin in acute, chronic or cancer pain were identified by MEDLINE (1966 to Nov 2004), EMBASE (1994 to Nov 2004), SIGLE (1980 to Jan 2004) and the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2004). Additional studies were identified from the reference list of the retrieved papers, and by contacting investigators. Date of most recent search: January 2004.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent review authors, and trials were quality scored. Numbers-needed-to-treat-to-benefit (NNTs) were calculated, where possible, from dichotomous data for effectiveness, adverse effects and drug-related study withdrawal.

MAIN RESULTS

Fourteen reports describing 15 studies of gabapentin were considered eligible (1468 participants). One was a study of acute pain. The remainder included the following conditions: post-herpetic neuralgia (two studies), diabetic neuropathy (seven studies), a cancer related neuropathic pain (one study) phantom limb pain (one study), Guillain Barré syndrome (one study), spinal chord injury pain (one study) and various neuropathic pains (one study).The study in acute post-operative pain (70 participants) showed no benefit for gabapentin compared to placebo for pain at rest.In chronic pain, the NNT for improvement in all trials with evaluable data is 4.3 (95% CI 3.5 to 5.7). Forty two percent of participants improved on gabapentin compared to 19% on placebo. The number needed to harm (NNH) for adverse events leading to withdrawal from a trial was not significant. Fourteen percent of participants withdrew from active arms compared to 10% in placebo arms. The NNH for minor harm was 3.7 (95% CI 2.4 to 5.4). The NNT for effective pain relief in diabetic neuropathy was 2.9 (95% CI 2.2 to 4.3) and for post herpetic neuralgia 3.9 (95% CI 3 to 5.7).

AUTHORS' CONCLUSIONS

There is evidence to show that gabapentin is effective in neuropathic pain. There is limited evidence to show that gabapentin is ineffective in acute pain.

Effectiveness of the association between carbamazepine and peripheral analgesic block with ropivacaine for the treatment of trigeminal neuralgia

Treatment of trigeminal neuralgia (TN) is achieved by using adjuvant analgesics like antiepileptics, with carbamazepine (CBZ) being the first-line approach for TN patients, although side effects may be present. Other approaches using gabapentin, namely when associated with peripheral analgesic block of TN trigger points with the local anesthetic ropivacaine (ROP), resulted in decreased pain and daily drug intake (reduced side effects). This study evaluates if the association between CBZ and the peripheral block with ROP reinforces the clinical value of CBZ. In this parallel, double-blinded study, idiopathic TN patients were randomized to receive during 4 weeks either CBZ (CBZ; n = 21) or CBZ associated with the peripheral analgesic block using ROP (CBZ + ROP; n = 24). The primary outcome measures were the following: i) pain intensity, evaluated by the numerical rating scale; ii) number of pain crises; and iii) number needed to treat. Evaluation points were at the beginning (day 1) and end (day 29) of treatment and after a follow-up of 5 months (month 6). Both protocols resulted in a decrease of pain intensity and number of pain crises, but only the association CBZ + ROP showed i) a significant stronger reduction in pain intensity at month 6 and ii) a significant decrease in the daily dose of CBZ given to patients (both at day 29 and month 6). In contrast, the daily dose in CBZ-only patients remained constant or even increased. The number needed to treat for the association CBZ + ROP over the CBZ protocol reduced from 5 at the end of the 4-week treatment to 3 after the 5-month follow-up. Data reinforce the use of CBZ as a primary tool to control pain in TN patients, as the association CBZ + ROP i) improves the clinical qualities of CBZ, ii) strongly reduces the daily dose of CBZ, and iii) reduces the potential side effects attributed to high doses of CBZ.

Pharmacological management of pain in patients with multiple sclerosis

Multiple sclerosis (MS) is an inflammatory, demyelinating, autoimmune disease of the CNS. There are currently a number of disease-modifying medications for MS that modulate or suppress the immune system; however, these medications do not directly relieve MS symptoms, which include visual deficits, gait problems, sensory deficits, weakness, tremor, spasticity and pain, among others. Pain is a common symptom in MS which has recently been estimated to be experienced by more than 40% of patients. Nociceptive pain occurs as an appropriate physiological response transmitted to a conscious level when nociceptors in bone, muscle or any body tissue are activated, warning the organism of tissue damage. Neuropathic pain is initiated as a direct consequence of a lesion or disease affecting the somatosensory system, with no physiological advantage. Nociceptive and neuropathic pain in MS may be present concurrently and at different stages of the disease, and may be associated with other symptoms. Central neuropathic pain has been reported to be among the most common pain syndromes in MS. It is described as constant, often spontaneous, burning occurring more frequently in the lower limbs. Treatment typically includes tricyclic antidepressants and antiepileptic medications, although studies have been conducted in relatively small samples and optimal dosing has not been confirmed. Cannabinoids have been among the few treatments studied in well designed, randomized, placebo-controlled trials for central neuropathic pain. In the largest of these trials, which included 630 subjects, a 15-week comparison between Delta9-tetrahydrocannabinol and placebo was performed. More patients receiving active treatment perceived an improvement in pain than those receiving placebo, although approximately 20% of subjects reported worsening of pain while on active treatment. Trigeminal neuralgia, while affecting less than 5% of patients with MS, is the most studied pain syndrome. The pain can be extreme and is typically treated with carbamazepine, although adverse effects can mimic an MS exacerbation. Painful topic spasms occur in approximately 11% of the MS population and are treated with antispasticity medications such as baclofen and benzodiazepines. Gabapentin has also demonstrated efficacy, but all studies have included small sample sizes. In general, evidence for treating pain in MS is limited. Many clinical features of pain are often unrecognized by clinicians and are difficult for patients to describe. Treatment is often based on anecdotal reports and clinical experience. We present a review of treatment options for pain in MS, which should serve to update current knowledge, highlight shortcomings in clinical research and provide indications towards achieving evidence-based treatment of pain in MS.

Medical management of trigeminal neuropathic pains

IMPORTANCE OF THE FIELD

Although trigeminal neuralgia has traditionally been considered the prime neuralgic condition in the face region, other forms of neuropathic pain are now being more frequently recognized and require recognition and a different management approach.

AREAS COVERED IN THIS REVIEW

This review principally covers medical management of trigeminal neuralgia; but also included is glossopharyngeal neuralgia, trigeminal neuropathic pain (atypical odontalgia) and burning mouth syndrome. Systematic reviews and guidelines will be discussed.

WHAT THE READER WILL GAIN

An update will be provided of drug therapy for these relatively rare facial pains.

TAKE HOME MESSAGE

Trigeminal neuralgia continues to be best managed using anticonvulsant drugs, the primary ones being carbamazepine and oxcarbazepine; baclofen may be helpful and, of the newly emerging drugs, pregabalin has potential. Glossopharyngeal neuralgia remains managed in the same way as trigeminal neuralgia. Trigeminal neuropathic pain is probably best managed according to guidelines used for the management of neuropathic pain, which include the use of tricyclic antidepressants, gabapentin, pregabalin, duloxetine, venalafaxine and topical lidocaine. Burning mouth syndrome is a neuropathic pain managed initially with topical clonazepam and then with other neuropathic drugs. Patients need to be involved in their management.

Newer Anticonvulsant Drugs in Neuropathic Pain and Bipolar Disorder

Older anticonvulsants have been used to manage both chronic pain and bipolar disorders. As the armamentarium of anticonvulsants increases, the role of the newer agents for pain or mood disorders is uncertain. This paper summarizes the clinical data available with gabapentin, lamotrigine, oxcarbazepine, tiagabine and topiramate for bipolar disorder and lamotrigine, oxcarbazepine, tiagabine and topiramate for neuropathic pain.

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.

AAN-EFNS guidelines on trigeminal neuralgia management

Several issues regarding diagnosis, pharmacological treatment, and surgical treatment of trigeminal neuralgia (TN) are still unsettled. The American Academy of Neurology and the European Federation of Neurological Societies launched a joint Task Force to prepare general guidelines for the management of this condition. After systematic review of the literature the Task Force came to a series of evidence-based recommendations. In patients with TN MRI may be considered to identify patients with structural causes. The presence of trigeminal sensory deficits, bilateral involvement, and abnormal trigeminal reflexes should be considered useful to disclose symptomatic TN, whereas younger age of onset, involvement of the first division, unresponsiveness to treatment and abnormal trigeminal evoked potentials are not useful in distinguishing symptomatic from classic TN. Carbamazepine (stronger evidence) or oxcarbazepine (better tolerability) should be offered as first-line treatment for pain control. For patients with TN refractory to medical therapy early surgical therapy may be considered. Gasserian ganglion percutaneous techniques, gamma knife and microvascular decompression may be considered. Microvascular decompression may be considered over other surgical techniques to provide the longest duration of pain freedom. The role of surgery versus pharmacotherapy in the management of TN in patients with multiple sclerosis remains uncertain.

Current management of pain associated with multiple sclerosis

While pain is a common problem in patients with multiple sclerosis (MS), it is not frequently mentioned by patients and a more direct approach is required in order to obtain information about pain from patients. Many patients with MS experience more than one pain syndrome; combinations of dysaesthesia, headaches and/or back or muscle and joint pain are frequent. For each pain syndrome a clear diagnosis and therapeutic concept needs to be established. Pain in MS can be classified into four diagnostically and therapeutically relevant categories: (i) neuropathic pain due to MS (pain directly related to MS); (ii) pain indirectly related to MS; (iii) MS treatment-related pain; and (iv) pain unrelated to MS. Painful paroxysmal symptoms such as trigeminal neuralgia (TN), or painful tonic spasms are treated with antiepileptics as first choice, e.g. carbamazepine, oxcarbazepine, lamotrigine, gabapentin, pregabalin, etc. Painful 'burning' dysaesthesias, the most frequent chronic pain syndrome, are treated with TCAs such as amitriptyline, or antiepileptics such as gabapentin, pregabalin, lamotrigine, etc. Combinations of drugs with different modes of action can be particularly useful for reducing adverse effects. While escalation therapy may require opioids, there are encouraging results from studies regarding cannabinoids, but their future role in the treatment of MS-related pain has still to be determined. Pain related to spasticity often improves with adequate physiotherapy. Drug treatment includes antispastic agents such as baclofen or tizanidine and in patients with phasic spasticity, gabapentin or levetiracetam are administered. In patients with severe spasticity, botulinum toxin injections or intrathecal baclofen merit consideration. While physiotherapy may ameliorate malposition-induced joint and muscle pain, additional drug treatment with paracetamol (acetaminophen) or NSAIDs may be useful. Moreover, painful pressure lesions should be avoided by using optimally adjusted aids. Treatment-related pain associated with MS can occur with subcutaneous injections of interferon-beta or glatiramer acetate, and may be reduced by optimizing the injection technique and by local cooling. Systemic (particularly 'flu-like') adverse effects of interferons, e.g. myalgias, can be reduced by administering paracetamol, ibuprofen or naproxen. A potential increase in the frequency of pre-existing headaches after starting treatment with interferons may require optimization of headache attack therapy or even prophylactic treatment. Pain unrelated to MS, such as back pain or headache, is common in patients with MS and may deteriorate as a result of the disease. In summary, a careful analysis of each pain syndrome will allow the design of the appropriate treatment plan using various medical and nonmedical options (multimodal therapy), and will thus help to improve the quality of life (QOL) of the patients.

Efficacy of lamotrigine in the management of chemotherapy-induced peripheral neuropathy: a phase 3 randomized, double-blind, placebo-controlled trial, N01C3

BACKGROUND

Lamotrigine, an antiepileptic agent, has been reported as being effective in reducing symptoms of neuropathy associated with various etiologies. Based on such data, a multicenter double-blind, placebo-controlled, randomized trial was conducted to evaluate the effect of lamotrigine on pain and other neuropathic symptoms due to chemotherapy-induced peripheral neuropathy (CIPN).

METHODS

Patients with symptomatic CIPN with symptom scores of either 1) >3 on a 0-10 Numerical Rating Scale (NRS) or 2) >1 on the 0-3 the Eastern Cooperative Oncology Group (ECOG) neuropathy scale (ENS) were eligible (higher numbers corresponding to greater severity of symptoms in both scales). Patients were randomly assigned to receive lamotrigine (target dose of 300 mg/day) or placebo for 10 weeks. Endpoints were measured biweekly.

RESULTS

In all, 131 patients were enrolled. Both groups were well matched at baseline. Over the 10-week period of the trial, the average pain scores (NRS) for the lamotrigine and placebo arms declined in both arms, with no statistically significant difference noted between the changes in the 2 groups (0.3 and 0.5 unit reduction from baseline, respectively; P=.56). Similarly, decreases in the ENS with therapy were not statistically different (0.4 and 0.3, respectively; P=.3). Changes in other subjective symptom scales were also not found to be statistically different between the 2 groups. Toxicities were mild and similar in each group.

CONCLUSIONS

The results suggest that lamotrigine is not effective for relieving neuropathic symptoms in patients because of CIPN.

Trigeminal neuralgia: for one nerve a multitude of treatments

Trigeminal neuralgia (TN) is reputed to be one of the most painful conditions in human experience. Thus, many treatments, both medical and surgical, have been developed for this relapsing and remitting, paroxysmal stabbing or electrical, facial pain syndrome. The likely etiology in many cases is vascular compression of the trigeminal nerve root entry zone, leading to focal demyelination and aberrant neural discharges. MRI may disclose neurovascular contact, although not with sufficient sensitivity or specificity to substitute for careful clinical diagnosis. In treating TN, antiepileptic drugs are superior to traditional analgesics. Carbamazepine is the first choice drug. Additional drugs for which there is evidence of efficacy include oxcarbazepine, baclofen, gabapentin, lamotrigine and phenytoin. Many patients eventually experience tachyphylaxis or may not tolerate effective doses. Surgical options include: microvascular decompression; balloon compression; radiofrequency thermocoagulation or glycerol rhizotomies; and subcutaneous alcohol branch blockade. Stereotactic gamma knife radiosurgery is a further option. Motor cortex stimulation and transcranial magnetic stimulation, although having shown initial promise for trigeminal neuropathic pain, seem to be ineffective for classical TN. The choice of drug, whether or when to operate, and which procedure to choose should be individualized to the particular needs and conditions of the patient.

Evidence-based approach to the medical management of trigeminal neuralgia

Classical trigeminal neuralgia (TN) is a rare neuropathic pain with distinct diagnostic criteria. The aim of this review is to provide recommendations for medical management based on current evidence and provide some pointers on the conduct of future trials. A review of the literature identified four systematic reviews, of which one was a meta-analysis and 18 randomized controlled trials (RCT) on medical management of trigeminal neuralgia. The evidence suggests that carbamazepine is still the first line drug for medical management, but this should be changed to oxcarbazepine if there is poor efficacy and an unacceptable side effect profile. Combination of carbamazepine with lamotrigine or baclofen is the second line treatment when monotherapy fails, but the evidence is weak. An early neurosurgical opinion should be sought when a patient has a neurovascular contact of the trigeminal nerve, poor efficacy and tolerability of drug treatment and no remission periods. Many of the new antiepileptic drugs need to be evaluated in RCTs with innovative designs and robust outcome measures.

Management of neuropathic orofacial pain

Current management of painful trigeminal neuropathies relies on pharmacological (topical and systemic), surgical, and complementary modalities. There is, however, a lack of quality research relating to the effectiveness of these modalities. In this review we analyze the available data that relates to the therapy of trigeminal neuralgia, postherpetic neuralgia, and posttraumatic neuropathies and provide clinical guidelines. The review focuses on medical management, as well as surgical and other interventions for painful neuropathies.

Trigeminal neuralgia

The paroxysmal facial pain of trigeminal neuralgia is notoriously severe. Recent advances in medical science are achieving significant strides toward alleviating this incapacitating condition. High-resolution neuroimaging techniques are rendering detailed views of underlying neurovascular relationships. Newer antiepileptic medications and novel therapies are proving helpful in treating pain resistant to carbamazepine. Further developments also in targeted neurosurgical and radiosurgical techniques are providing pain relief within increasingly wider margins of safety. Much has been accomplished, yet much remains to be done.