Treatment of refractory trigeminal neuralgia with intravenous phenytoin

"Status trigeminal neuralgia": Analysis of 39 cases and proposal for diagnostic criteria

OBJECTIVE

The aim of this descriptive study was to propose diagnostic criteria for acute exacerbation of trigeminal neuralgia (TN) based on the analysis of retrospective cases.

BACKGROUND

TN is a rare and extremely painful condition whose evolution can be punctuated by major exacerbations, leading to significant functional impairment. Several denominations are used for these exacerbations: "acute exacerbation", "status of trigeminal neuralgia", and "status trigeminus". There is currently no clinical definition of this state. In this manuscript, we used the term "status trigeminal neuralgia" (STN).

METHODS

We conducted a retrospective study, in a tertiary care specialist headache center, in France. Patients were selected from January 2015 to October 2022, with the French translation of the keyword "STN", in the medical records (outpatients) or the codage for trigeminal neuralgia (inpatients). Additional cases of STN were prospectively recruited from October 2022 to February 2023. We analyzed the clinical and paraclinical data of these patients.

RESULTS

Thirty-nine patients presenting with STN were included. There was a preponderance of women (64%) with 24 cases of classic TN (62%) and 15 cases of secondary TN (38%). Concerning STN, 39 episodes were described. Pain was very severe in all patients. Cranial autonomic signs were present in 23% of cases. Pain extended beyond the usual territory in 44% of cases. A continuous pain background was present in 35% of cases. With regard to triggering factors, paroxysms of facial pain were triggered by eating (97% of patients), speaking (90%) or drinking (62% of patients). Repercussions on weight, hydration, or mood disorders were observed in 67%, 56% and 59% of the cases, respectively.

CONCLUSION

STN is a rare clinical presentation of TN. We proposed criteria and a new denomination for this condition.

Neuropathic Pain in the Emergency Setting: Diagnosis and Management

Neuropathic pain, traditionally considered a chronic condition, is increasingly encountered in the emergency department (ED), accounting for approximately 20% of patients presenting with pain. Understanding the physiology and key clinical presentations of neuropathic pain is crucial for ED physicians to provide optimal treatment. While diagnosing neuropathic pain can be challenging, emphasis should be placed on obtaining a comprehensive medical history and conducting a thorough clinical examination. Patients often describe neuropathic pain as a burning or shock-like sensation, leading them to seek care in the ED after ineffective relief from common analgesics such as paracetamol and NSAIDs. Collaboration between emergency medicine specialists, neurologists, and pain management experts can contribute to the development of evidence-based guidelines specifically tailored for the emergency department setting. This article provides a concise overview of the common clinical manifestations of neuropathic pain that may prompt patients to seek emergency care.

Multivariate models to predict pain recurrence and sensitive complications after percutaneous balloon compression in trigeminal neuralgia

OBJECTIVE

Percutaneous balloon compression (PBC) is a popular treatment option for trigeminal neuralgia. However, the efficacy of PBC is widely considered to be associated with the occurrence of sensitive complications, although neither this correlation nor the underlying mechanisms have been established. The objectives of the present study were to identify factors predicting time to pain recurrence after PBC and identify factors predicting a severe sensitive complication.

METHODS

The authors conducted a retrospective study on patients who underwent PBC for the first time between 1985 and 2019 in two French hospitals. Data were retrieved from patients' medical records. Potential clinical and radiological predictors for time to pain recurrence and severe sensitive complication were evaluated using a Cox model and a logistic regression, respectively.

RESULTS

A total of 131 patients were included in the study, with a median follow-up of 3.0 years. Pain recurrence occurred in 77 patients, and the median time to pain recurrence was 2.0 years. In the multivariate analysis, six independent factors predicting pain recurrence were identified: 1) longer duration of presurgical symptoms; 2) localization of the pain along the mandibular branch of the trigeminal nerve (V3); 3) atypical pain; 4) diagnosis of multiple sclerosis; 5) use of a medical device not specifically adapted for trigeminal neuralgia surgery; and 6) duration of balloon compression > 60 seconds. Regarding the secondary objective, 26 patients presented a severe sensitive complication after PBC, which the authors defined as the development of a new sensitivity disorder of the cornea, deafferentation pain known as anesthesia dolorosa, and/or long-lasting hypoesthesia augmentation characterized by the new appearance or increase in size or intensity of an area of hypoesthesia in the face for at least 3 months. The only predictor associated with a severe sensitive complication in the multivariate analysis was compression duration > 60 seconds.

CONCLUSIONS

These results show that the risk of postoperative complications can be assessed at the patient level, the most important modifiable parameter being the time of compression by the balloon. Although this study shows the relevance of a personalized medicine approach, its clinical application remains to be validated.

Intravenous Fosphenytoin Therapy as an Acute Rescue Treatment for Glossopharyngeal Neuralgia Crisis in Patients Awaiting Neurosurgical Procedures: A Case Series

INTRODUCTION

Few treatments exist for acute attacks of glossopharyngeal neuralgia (GPN). We investigated the efficacy of intravenous fosphenytoin therapy (IFT) during GPN crisis.

CASE PRESENTATION

We evaluated records of 4 consecutive patients with GPN awaiting microvascular decompression (MVD) who received IFT (total, 750 mg). Pain severity was evaluated using a Numerical Rating Scale (NRS). The score was 10 (maximum pain) before treatment. Case 1 (a 52-year-old woman, left GPN): for 12 hours after IFT, pain was eliminated (NRS 0/10); however, severe pain recurred 2 days later. She received MVD 9 days after IFT. Case 2 (a 72-year-old woman, right GPN): pain score reduced to 0/10 immediately after IFT and remained so for 2 days. Severe pain recurred, and she underwent MVD 4 days after IFT. Case 3 (a 69-year-old woman, right GPN): pain was reduced (NRS, 5/10) immediately after IFT and nearly eliminated (1/10) 1 hour later. After 6 hours, severe pain recurred; she received a second IFT 3 days later, and pain score dropped to 1/10. She was pain-free for 24 hours but intermediate pain recurred in 2 days. Microvascular decompression was performed 9 days after the second IFT. Case 4 (a 32-year-old woman, right GPN): Pain score reduced to 0/10 immediately after IFT and remained so for 4 days. She underwent MVD 4 days after IFT. No evidence of recurrence was found throughout the 24-, 22-, 20-, and 5-month follow-ups.

CONCLUSIONS

These results provide new insights into the innovative therapeutic option of intravenous fosphenytoin and contribute to advancements in treating acute GPN crisis.

Central Neuropathic Pain Syndromes: Current and Emerging Pharmacological Strategies

Central neuropathic pain is caused by a disease or lesion of the brain or spinal cord. It is difficult to predict which patients will develop central pain syndromes after a central nervous system injury, but depending on the etiology, lifetime prevalence may be greater than 50%. The resulting pain is often highly distressing and difficult to treat, with no specific treatment guidelines currently available. This narrative review discusses mechanisms contributing to central neuropathic pain, and focuses on pharmacological approaches for managing common central neuropathic pain conditions such as central post-stroke pain, spinal cord injury-related pain, and multiple sclerosis-related neuropathic pain. Tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and gabapentinoids have some evidence for efficacy in central neuropathic pain. Medications from other pharmacologic classes may also provide pain relief, but current evidence is limited. Certain non-pharmacologic approaches, neuromodulation in particular, may be helpful in refractory cases. Emerging data suggest that modulating the primary afferent input may open new horizons for the treatment of central neuropathic pain. For most patients, effective treatment will likely require a multimodal therapy approach.

Intravenous lacosamide and phenytoin for the treatment of acute exacerbations of trigeminal neuralgia: A retrospective analysis of 144 cases

Background

Scant evidence is available on the use of intravenous pain treatment in acute exacerbations of trigeminal neuralgia. The aim of this descriptive study was to evaluate the effectiveness and security of intravenous lacosamide and phenytoin in the treatment of acute trigeminal neuralgia pain.

Methods

We reviewed patients who attended the emergency department of a tertiary hospital between 2012 and 2020 for exacerbations of trigeminal neuralgia pain and were treated with either intravenous phenytoin or lacosamide for the first time. Primary endpoints were pain relief and adverse effects during the hospital stay. A comparative analysis between both treatment groups was performed.

Results

We studied 144 episodes in 121 patients (median age 61 years, 66.1% women). Trigeminal neuralgia etiology was secondary in 9.9%. Pain relief was observed in 77.8% of 63 patients receiving lacosamide infusions, and adverse effects in 1.6%. Pain relief was observed in 72.8% of 81 phenytoin infusions and adverse effects in 12.3%, all mild. No difference was observed in pain relief between groups, but the proportion of adverse effects was significantly different (p = 0.023). Statistically significant differences were also detected in readmissions within six months, time to readmission, and pain relief status at first follow-up visit.

Conclusion

Intravenous lacosamide and phenytoin can be effective and safe treatments for acute pain in trigeminal neuralgia. According to our series, lacosamide might be better tolerated than phenytoin and lead to lower readmissions and sustained pain relief.

Intravenous fosphenytoin as treatment for acute exacerbation of trigeminal neuralgia: A prospective systematic study of 15 patients

INTRODUCTION

Intravenous fosphenytoin is widely used for acute exacerbation of trigeminal neuralgia, however, few studies have investigated this treatment. We aimed to examine the efficacy and side effects of initial intravenous fosphenytoin plus oral tapering of phenytoin for exacerbation of trigeminal neuralgia.

METHODS

Consecutive patients with primary trigeminal neuralgia were included in this prospective observational 90-days follow-up study. Data were collected using standardized interviews before, at 24 hours, day 7, 30 and 90 post loading dose. The primary outcome was the proportion of responders defined as a 50% reduction in pain intensity 24 hours post loading dose.

RESULTS

We included 15 patients. Nine patients (60%) were responders. Pain intensity 24 hours post loading dose was reduced by 5.00 points on the numerical rating scale (p < 0.001), and at day 7 by 5.5 points (p < 0.001). The most common side effects were hypotension and dizziness.

CONCLUSION

Intravenous fosphenytoin relieves trigeminal neuralgia pain in most patients and provides a window for titrating prophylactic trigeminal neuralgia medications or planning neurosurgery. The decision to administer intravenous fosphenytoin should be taken with support from trigeminal neuralgia experts and involves considerations of co-morbidities and other treatment options for acute exacerbation of trigeminal neuralgia.Clinical Trial: Preregistered (ClinicalTrials.gov Identifier: NCT03712254.

Intravenous fosphenytoin therapy for rescue of acute trigeminal neuralgia crisis in patients awaiting neurosurgical procedures: A cross-sectional study

Few treatments exist for acute attacks of trigeminal neuralgia. Therefore, this study aimed to investigate the efficacy and safety of an intravenous fosphenytoin therapy protocol in a trigeminal neuralgia crisis. We conducted a single-center, retrospective, observational study of the records of 20 patients with trigeminal neuralgia who received intravenous fosphenytoin therapy (15 mg/mL in normal saline at 50 mg/min for 15 min, total 750 mg) during hospitalization between September 2015 and August 2020. Serum phenytoin concentration was measured 30 min post-infusion. Pain severity was evaluated using a numerical rating scale and was analyzed for statistical significance. The mean age of the patients was 67.5 years (female, 50.0%). The median numerical rating scale score (interquartile range) of pain severity was 2.35 (0-10), 0.65 (0-5), 0.15 (0-1), 2.00 (0-8), and 4.30 (0-10) at 15, 30, and 60 min, and 12 and 24 h, respectively (p < .001); the numerical rating scale score was 10 before treatment. Reduction in pain 24 h following treatment was significant. The mean phenytoin concentration was 12.8 μg/mL 30 min post-treatment. While mild dizziness occurred in four patients, all could walk independently within 60 min. The mean age and weight of patients with mild dizziness were significantly higher and lower, respectively (p < .001), than those of other patients. These results may provide physicians with new insights into the innovative therapeutic option of intravenous fosphenytoin and contribute to advancements in treating acute trigeminal neuralgia crisis.

Trigeminal Neuralgia: Current Approaches and Emerging Interventions

Trigeminal neuralgia (TN) has been described in the literature as one of the most debilitating presentations of orofacial pain. This review summarizes over 150 years of collective clinical experience in the medical and surgical treatment of TN. Fundamentally, TN remains a clinical diagnosis that must be distinguished from other types of trigeminal neuropathic pain and/or facial pain associated with other neuralgias or headache syndromes. What is increasingly clear is that there is no catch-all medical or surgical intervention that is effective for all patients with trigeminal neuralgia, likely reflective of the fact that TN is likely a heterogenous group of disorders that jointly manifests in facial pain. The first-line treatment for TN remains anticonvulsant medical therapy. Patients who fail this have a range of surgical options available to them. In general, microvascular decompression is a safe and effective procedure with immediate and durable outcomes. Patients who are unable to tolerate general anesthesia or whose medical comorbidities preclude a suboccipital craniectomy may benefit from percutaneous methodologies including glycerol or radiofrequency ablation, or both. For patients with bleeding diathesis due to blood thinning medications who are ineligible for invasive procedures, or for those who are unwilling to undergo open surgical procedures, radiosurgery may be an excellent option-provided the patient understands that maximum pain relief will take on the order of months to achieve. Finally, peripheral neurectomies continue to provide an inexpensive and resource-sparing alternative to pain relief for patients in locations with limited economic and medical resources. Ultimately, elucidation of the molecular mechanisms underlying trigeminal neuralgia will pave the way for novel, more effective and less invasive therapies.

Trigeminal Neuralgia: Basic and Clinical Aspects

The trigeminal nerve is the largest of all cranial nerves. It has three branches that provide the main sensory innervation of the anterior two-thirds of the head and face. Trigeminal neuralgia (TN) is characterized by sudden, severe, brief, and stabbing recurrent episodes of facial pain in one or more branches of the trigeminal nerve. Pain attacks can occur spontaneously or can be triggered by non-noxious stimuli, such as talking, eating, washing the face, brushing teeth, shaving, a light touch or even a cool breeze. In addition to pain attacks, a proportion of the patients also experience persistent background pain, which along with autonomic signs and prolonged disease duration, represent predictors of worse treatment outcomes. It is now widely accepted that the presence of a neurovascular compression at the trigeminal root entry zone is an anatomic abnormality with a high correlation with classical TN. However, TN may be related to other etiologies, thus presenting different and/or additional features. Since the 1960s, the anticonvulsant carbamazepine is the drug of choice for TN treatment. Although anti-epileptic drugs are commonly used to treat neuropathic pain in general, the efficacy of carbamazepine has been largely limited to TN. Carbamazepine, however, is associated with dose-limiting side-effects, particularly with prolonged usage. Thus, a better understanding and new treatment options are urgently warranted for this rare, but excruciating disease.

Trigeminal Neuralgia Crisis - Intravenous Phenytoin as Acute Rescue Treatment

OBJECTIVE

The aim of this retrospective cohort study was to analyze responses to intravenous (IV) phenytoin (PHT) for trigeminal neuralgia (TN) crisis in a group of patients treated at our institution.

BACKGROUND

TN is one of the most common causes of facial pain. Its treatment relies on preventive therapy with either carbamazepine or oxcarbazepine. During severe pain episodes, patients may be unable to eat, drink, or even swallow oral medication, requiring in-hospital treatment. There is scarce evidence to support IV medication use for TN, making management of this condition difficult.

METHODS

We reviewed clinical records of patients with TN crisis consulting the emergency department at a tertiary neurological referral center in Buenos Aires, Argentina, treated with IV PHT as analgesic strategy, and with at least 1-month posttreatment follow-up. Demographic features, magnetic resonance imaging findings, and therapeutic management were analyzed.

RESULTS

Thirty-nine patients with TN were included, 18 (46.2%) receiving IV PHT more than once (total number of infusions administered, 65). Immediate pain relief was observed in 89.2% (58/65) and 15.4% (10/65) presented side effects.

CONCLUSIONS

We recommend IV PHT as acute rescue treatment in TN crisis.

A systematic review of rescue analgesic strategies in acute exacerbations of primary trigeminal neuralgia

BACKGROUND

Trigeminal neuralgia (TN) can have a significant impact on wellbeing and quality of life. Limited data exist for treatments that improve TN pain acutely, within 24 h of administration. This systematic review aims to identify effective treatments that acutely relieve TN exacerbations.

METHODS

We searched Medline and Cochrane Central Register of Controlled Trials (CENTRAL) for relevant English language publications. The reference list for all articles was searched for other relevant publications. All studies that satisfied the following PICO criteria were included: (i) Population-adults with acute exacerbation of primary TN symptoms; (ii) Intervention-any medication or intervention with the primary goal of pain relief within 24 h; (iii) Comparator-usual medical care, placebo, sham or active treatment; (iv) Outcome-more than 50% reduction in pain intensity within 24 h of administration.

RESULTS

Of 431 studies, 17 studies were identified that reported immediate results of acute treatment in TN. The evidence suggests that the following interventions may be beneficial: local anaesthetic, mainly lidocaine (ophthalmic, nasal or oral mucosa, trigger point injection, i.v. infusion, nerve block); anticonvulsant, phenytoin or fosphenytoin (i.v. infusion); serotonin agonist, sumatriptan (s.c. injection, nasal). Other referenced interventions with very limited evidence include N-methyl-d-aspartate receptor antagonist (magnesium sulphate infusion) and botulinum toxin (trigger point injection).

CONCLUSIONS

Several treatment options exist that may provide fast and safe relief of TN. Future studies should report on outcomes within 24 h to improve knowledge of the acute analgesic TN treatments.

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.

Refining the Benefit/Risk Profile of Anti-Epileptic Drugs in Headache Disorders

Anti-epileptic drugs are among the most effective drugs for migraine prophylaxis, and will likely continue to have a role even as new therapies emerge. Topiramate and valproate are effective for the preventive treatment of migraine, and other medications such as gabapentin or lamotrigine may have a role in the treatment of those with allodynia or frequent aura, respectively. Oxcarbazepine, carbamazepine, phenytoin, gabapentin, and others may alleviate pain in trigeminal neuralgia. While many anti-epileptic drugs can be effective in those with migraine or other headaches, most of these agents can potentially cause serious side effects. In particular, valproate, topiramate, carbamazepine, and phenytoin may lead to adverse outcomes for infants of exposed mothers. Valproate should not be given to women of childbearing potential for migraine prevention.

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, Glossopharyngeal Neuralgia, and Myofascial Pain Dysfunction Syndrome: An Update

Neuropathic pain is a common phenomenon that affects millions of people worldwide. Maxillofacial structures consist of various tissues that receive frequent stimulation during food digestion. The unique functions (masticatory process and facial expression) of the maxillofacial structure require the exquisite organization of both the peripheral and central nervous systems. Neuralgia is painful paroxysmal disorder of the head-neck region characterized by some commonly shared features such as the unilateral pain, transience and recurrence of attacks, and superficial and shock-like pain at a trigger point. These types of pain can be experienced after nerve injury or as a part of diseases that affect peripheral and central nerve function, or they can be psychological. Since the trigeminal and glossopharyngeal nerves innervate the oral structure, trigeminal and glossopharyngeal neuralgia are the most common syndromes following myofascial pain dysfunction syndrome. Nevertheless, misdiagnoses are common. The aim of this review is to discuss the currently available diagnostic procedures and treatment options for trigeminal neuralgia, glossopharyngeal neuralgia, and myofascial pain dysfunction syndrome.

Trigeminal Neuralgia

Trigeminal neuralgia (TN) is a sudden, severe, brief, stabbing, and recurrent pain within one or more branches of the trigeminal nerve. Type 1 as intermittent and Type 2 as constant pain represent distinct clinical, pathological, and prognostic entities. Although multiple mechanism involving peripheral pathologies at root (compression or traction), and dysfunctions of brain stem, basal ganglion, and cortical pain modulatory mechanisms could have role, neurovascular conflict is the most accepted theory. Diagnosis is essentially clinically; magnetic resonance imaging is useful to rule out secondary causes, detect pathological changes in affected root and neurovascular compression (NVC). Carbamazepine is the drug of choice; oxcarbazepine, baclofen, lamotrigine, phenytoin, and topiramate are also useful. Multidrug regimens and multidisciplinary approaches are useful in selected patients. Microvascular decompression is surgical treatment of choice in TN resistant to medical management. Patients with significant medical comorbidities, without NVC and multiple sclerosis are generally recommended to undergo gamma knife radiosurgery, percutaneous balloon compression, glycerol rhizotomy, and radiofrequency thermocoagulation procedures. Partial sensory root sectioning is indicated in negative vessel explorations during surgery and large intraneural vein. Endoscopic technique can be used alone for vascular decompression or as an adjuvant to microscope. It allows better visualization of vascular conflict and entire root from pons to ganglion including ventral aspect. The effectiveness and completeness of decompression can be assessed and new vascular conflicts that may be missed by microscope can be identified. It requires less brain retraction.

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.

Therapeutic efficacy and safety of botulinum toxin type A in trigeminal neuralgia: a systematic review

Trigeminal neuralgia is a common disorder caused mainly by compression of the trigeminal nerve root by an overlying blood vessel. Pharmacotherapy and surgery are ineffective or unsuitable in many patients. Therefore, other therapeutic modalities have been tried, including injection of botulinum toxin type A (BTX-A). This study aims to systematically review the therapeutic efficacy and safety of BTX-A in trigeminal neuralgia. PubMed, EMBASE, Cochrane Library Clinical Trials and Web of Science from January 1966 to March 2013 were searched with the terms of “botulinum toxin” AND “trigeminal neuralgia”, and references of related articles were traced. Data on the efficacy and safety of BTX-A in this disorder were extracted and analyzed by at least 2 reviewers. Data for individual studies were reported, and pooled data were analyzed if appropriate. Five prospective studies and one double-blind, randomized, placebo-controlled study were identified. Response was achieved in approximately 70-100% of patients, and the mean pain intensity and frequency were reduced by approximately 60-100% at 4 weeks after treatment in most studies. Major adverse events were not reported. Available studies show BTX-A may be effective in treatment of trigeminal neuralgia. However, well-designed randomized, controlled, double-blinded trial is still lacking. Future BTX-A treatment studies on optimal dose, duration of the therapeutic efficacy, common AEs, and the time and indications for repeat injection would be promising.

Phenytoin for neuropathic pain and fibromyalgia in adults

BACKGROUND

Antiepileptic drugs have been used in pain management since the 1960s; some have shown efficacy in treating different neuropathic pain conditions. Phenytoin is an established antiepileptic drug that has been used occasionally to treat intractable trigeminal neuralgia.

OBJECTIVES

To assess the analgesic efficacy and adverse effects of the antiepileptic drug phenytoin in neuropathic pain and fibromyalgia.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 2), MEDLINE, and EMBASE to 28 February 2012, together with reference lists of retrieved papers and reviews, and ClinicalTrials.gov.

SELECTION CRITERIA

We planned to include randomised, double-blind studies of eight weeks duration or longer, comparing phenytoin with placebo or another active treatment in chronic neuropathic pain or fibromyalgia.

DATA COLLECTION AND ANALYSIS

Two review authors would independently extract data for efficacy and adverse events, and examine issues of study quality.

MAIN RESULTS

We did not identify any studies that satisfied the inclusion criteria.

AUTHORS' CONCLUSIONS

This review uncovered no evidence of sufficient quality to support the use of phenytoin in chronic neuropathic pain or fibromyalgia.