Dose comparison trial of sustained-release fampridine in multiple sclerosis

Critical Appraisal of Evidence for Improving Gait Speed in People with Multiple Sclerosis: Dalfampridine Versus Gait Training

BACKGROUND

Research has not yet compared the treatment effects of dalfampridine with traditional rehabilitation of gait impairments in multiple sclerosis (MS). The purpose of this review was to critically appraise the evidence for dalfampridine and gait training for increasing gait speed in people with MS.

METHODS

A systematic search of the research literature was conducted. Consideration was given to only randomized controlled trials (RCTs), systematic reviews, and meta-analyses. For selection of gait training studies, only studies involving task-specific gait training interventions and measuring treatment effects on gait speed were considered.

RESULTS

Treatment effects on gait speed were extracted from four studies examining the efficacy of dalfampridine and six gait training RCTs. Overall mean increase in gait speed with dalfampridine was 0.07 m/s (95% confidence interval [CI], 0.04-0.09 m/s) compared to 0.06 m/s (95% CI, 0.02-0.10 m/s) for gait training. Among dalfampridine responders (38% of participants in RCTs), the mean increase in gait speed was 0.16 m/s (95% CI, 0.13-0.18 m/s). Mean increases for individual gait training interventions ranged from 0.01 to 0.39 m/s; however, CIs were wide due to small sample sizes.

CONCLUSIONS

Current evidence is insufficient to conclude whether dalfampridine or gait training is superior for improving gait speed in people with MS. These findings should be viewed cautiously due to differences in study populations and small sample sizes in gait training studies. Both treatment approaches provide only short-lived improvements. Head-to-head comparison trials and studies combining both treatment modalities are needed.

Fatigue Management in Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory-demyelinating disease of the central nervous system that may entail severe levels of disability in the long term. However, independently of the level of disability, MS patients frequently experience severe fatigue that can be as disabling as objective neurological deficits. For that reason, it is mandatory to perform an early diagnosis of MS-related fatigue and start a suitable treatment as soon as possible. In clinical practice, MS-related fatigue should be assessed and managed by a multidisciplinary team involving neurologists, MS nurses, occupational therapists, and physiotherapists. When assessing a person with MS-related fatigue, the first step is to rule out potential triggers or causes of fatigue, which may be related to MS, such as urinary dysfunction, pain, or muscular spasms leading to a sleep disorder, or unrelated to it. Once these causes have been ruled out and appropriately tackled, a careful therapeutic intervention needs to be decided. Therapeutic interventions for MS-related fatigue can be pharmacological or non-pharmacological. Regarding the pharmacological treatments, although many drugs have been tested in clinical trials, only amantadine is currently recommended for this indication. Regarding the non-pharmacological approaches, they can be broadly divided into physical, psychological, and mixed physical/psychological interventions. Several studies, many of them randomised clinical trials, support the use of all these types of non-pharmacological interventions to treat MS-related fatigue. Recent publications suggest that the implementation of mixed approaches, which have a naturally comprehensive nature, may have excellent results in clinical practice, in relation not only to fatigue levels but also to more general aspects of MS.

Clinical response and tolerability of fampridine in clinical practice

Background: Gait disorder is very prevalent in multiple sclerosis. After 15 years of disease progression, 50% of patients need assistive devices for walking. Materials & methods: We performed a multicenter observational study, including multiple sclerosis patients with an Expanded Disability Status Scale score between 4.0 and 7.0, normal kidney function and no previous history of seizures. Results: The study sample comprised 138 patients with average age of 50.3 years median Expanded Disability Status Scale of 6.0. After treatment, a significant reduction was observed in both the Timed 25-Foot Walk test (baseline, 20.3 s; 14 days, 13.2 s; p < 0.001; 3 months, 12.1 s; p < 0.001) and the 12-Item Multiple Sclerosis Walking Scale score (baseline, 82.3; 14 days, 59.4; p < 0.001; 3 months, 57.2; p < 0.001). Adverse events were recorded in 39.9% of patients.

A guide to treating gait impairment with prolonged-release fampridine (Fampyra®) in patients with multiple sclerosis

INTRODUCTION

Gait impairment, a frequent sign in multiple sclerosis (MS), places a major burden on patients since it results in progressive loss of personal and social autonomy, along with work productivity. This guide aims to provide recommendations on how to evaluate gait impairment and use prolonged-release fampridine (PR-fampridine) as treatment for MS patients with gait impairment in Spain.

DEVELOPMENT

PR-fampridine dosed at 10mg every 12hours is currently the only drug approved to treat gait impairment in adults with MS. Additionally, PR-fampridine has been shown in clinical practice to significantly improve quality of life (QoL) in patients who respond to treatment. Treatment response can be assessed with the Timed 25-Foot Walk (T25FW) or the 12-item MS Walking Scale (MSWS-12); tests should be completed before and after starting treatment. The minimum time recommended for evaluating treatment response is 2 weeks after treatment onset. Patients are considered responders and permitted to continue the treatment when they demonstrate a decrease in their T25FW time or an increase in MSWS-12 scores. A re-evaluation is recommended at least every 6 months. The SF-36 (Short Form-36) and the MSIS-29 (MS Impact Scale-29) tests are recommended for clinicians interested in performing a detailed QoL assessment. This drug is generally well-tolerated and has a good safety profile. It should be taken on an empty stomach and renal function must be monitored regularly.

CONCLUSIONS

These recommendations will help ensure safer and more efficient prescription practices and easier management of PR-fampridine as treatment for gait impairment in Spanish adults with MS.

Dynamic walking features and improved walking performance in multiple sclerosis patients treated with fampridine (4-aminopyridine)

BACKGROUND

Impaired walking capacity is a frequent confinement in Multiple Sclerosis (MS). Patients are affected by limitations in coordination, walking speed and the distance they may cover. Also abnormal dynamic walking patterns have been reported, involving continuous deceleration over time. Fampridine (4-aminopyridine), a potassium channel blocker, may improve walking in MS. The objective of the current study was to comprehensively examine dynamic walking characteristics and improved walking capacity in MS patients treated with fampridine.

METHODS

A sample of N = 35 MS patients (EDSS median: 4) underwent an electronic walking examination prior to (Time 1), and during treatment with fampridine (Time 2). Patients walked back and forth a distance of 25 ft for a maximum period of 6 min (6-minute 25-foot-walk). Besides the total distance covered, average speed on the 25-foot distance and on turns was determined separately for each test minute, at Time 1 and Time 2.

RESULTS

Prior to fampridine administration, 27/35 patients (77 %) were able to complete the entire 6 min of walking, while following the administration, 34/35 patients (97 %) managed to walk for 6 min. In this context, walking distance considerably increased and treatment was associated with faster walking and turning across all six test minutes (range of effect sizes: partial eta squared = .34-.72). Importantly, previously reported deceleration across test minutes was consistently observable at Time 1 and Time 2.

DISCUSSION

Fampridine administration is associated with improved walking speed and endurance. Regardless of a treatment effect of fampridine, the previously identified, abnormal dynamic walking feature, i.e. the linear decline in walking speed, may represent a robust feature.

CONCLUSIONS

The dynamic walking feature might hence be considered as a candidate for a new outcome measure in clinical studies involving interventions other than symptomatic treatment, such as immune-modulating medication.

TRIAL REGISTRATION

DRKS00009228 (German Clinical Trials Register). Date obtained: 25.08.2015.

Reducing falls and improving mobility in multiple sclerosis

Falls are common in persons with multiple sclerosis (MS), and are related to physical injury and reduce the quality of life. Mobility impairments are a significant risk factor for falls in persons with MS. Although there is evidence that mobility in persons with MS can be improved with rehabilitation, much less is known about fall prevention. This review focuses on fall prevention in persons with MS. Ten fall prevention interventions consisting of 524 participants with a wide range of disability were systematically identified. Nine of the 10 investigations report a reduction in falls and/or proportion of fallers following treatment. The vast majority observed an improvement in balance that co-occurred with the reduction in falls. Methodological limitations preclude any firm conclusions. Numerous gaps in the understanding of fall prevention in persons with MS are discussed. Well-designed randomized control trials targeting mobility and falls are warranted.

Effects of functional electrical stimulation on gait function and quality of life for people with multiple sclerosis taking dalfampridine

BACKGROUND

Multiple sclerosis (MS) can adversely affect gait, causing gait slowing, loss of balance, decreased functional mobility, and gait deficits, such as footdrop. Current treatments for gait dysfunction due to MS are pharmacologic, using dalfampridine, or orthotic, using an ankle-foot orthosis. Functional electrical stimulation (FES) to the fibular nerve stimulates active dorsiflexion and provides an alternative treatment for gait dysfunction caused by footdrop. The objective of this study was to determine the effect of FES on gait function and the impact of MS on walking and quality of life for people with MS taking a stable dalfampridine dose.

METHODS

Participants demonstrating gait slowing and footdrop completed the Timed 25-Foot Walk (T25FW) test, 6-Minute Walk (6MW) test, GaitRite Functional Ambulation Profile, 12-item Multiple Sclerosis Walking Scale (MSWS-12), and 36-item Short Form Health Status Survey (SF-36) at screening without FES; the measures were repeated with FES at baseline, 1 month, and 3 months.

RESULTS

Twenty participants (8 men and 12 women) completed this unblinded case series study. The mean age, duration of MS, and time taking dalfampridine were 51.7, 15.8, and 1.4 years, respectively. Changes from screening to baseline and screening to 3 months were analyzed. Significant improvement was noted from screening to baseline for the MSWS-12 (P = .024) and SF-36 Physical Function domain (P = .028) and from screening to 3 months for the T25FW (P = .015), MSWS-12 (P = .003), and SF-36 Physical Function (P = .032) and Role Limitation-Physical Health (P = .012) domains.

CONCLUSIONS

Improvements above those induced pharmacologically suggest that FES can augment pharmacologic intervention and significantly improve gait function, decrease the impact of MS on walking, and improve quality of life for people with MS.

A pooled analysis of two phase 3 clinical trials of dalfampridine in patients with multiple sclerosis

BACKGROUND

Two phase 3 clinical trials demonstrated that dalfampridine extended-release 10-mg tablets (D-ER), twice daily, significantly improved walking relative to placebo in patients with multiple sclerosis (MS). The objective of this study was to evaluate the efficacy and safety of D-ER in patients with MS using pooled data from the two phase 3 trials.

METHODS

Data were pooled from the two trials, and D-ER was compared with placebo for timed-walk responder rate, changes in walking speed, and the 12-item Multiple Sclerosis Walking Scale (MSWS-12). Response rates were evaluated with respect to demographic and clinical characteristics.

RESULTS

D-ER had a significantly higher proportion of timed-walk responders relative to placebo (37.6% vs. 8.9%; P < .0001). The responder rate was independent of age, gender, race, body-mass index, type of MS, duration of MS, baseline Expanded Disability Status Scale score, baseline walking speed, and concomitant use of immunomodulatory therapies. Significant improvements were observed in walking speed and in MSWS-12 score for the pooled D-ER group compared with placebo. The safety profile was consistent with the individual studies; no new safety or tolerability concerns were identified.

CONCLUSIONS

D-ER demonstrated efficacy for the improvement of walking in patients with MS; response was independent of demographic and clinical characteristics.

Development of dalfampridine, a novel pharmacologic approach for treating walking impairment in multiple sclerosis

Walking impairment is a clinical hallmark of multiple sclerosis (MS). Dalfampridine-ER, an extended-release formulation of dalfampridine (also known by its chemical name, 4-aminopyridine, and its international nonproprietary name, fampridine), was developed to maintain drug plasma levels within a narrow therapeutic window, and assessed for its ability to improve walking in MS. The putative mechanism of action of dalfampridine-ER is restoration of axonal conduction via blockade of the potassium channels that become exposed during axonal demyelination. Two pivotal phase III clinical trials demonstrated that dalfampridine-ER 10-mg tablets administered twice daily improved walking speed and patient-reported perceptions of walking in some patients. Dalfampridine-ER was generally well tolerated, and, at the approved dose, risk of seizure was neither elevated relative to placebo nor higher than the rate in the MS population. Dalfampridine-ER (AMPYRA®) was approved in the United States for the treatment of walking in patients with MS as demonstrated by an increase in walking speed. The use of the dalfampridine-ER is contraindicated in patients with a history of seizure. It is the first pharmacologic therapy for this indication and has been incorporated into clinical management of MS.

Sustained-release fampridine (4-aminopyridine) in multiple sclerosis: efficacy and impact on motor function

Objective

The aim of this study was to determine the efficacy of sustained-release fampridine (4-aminopyridine) in veterans with multiple sclerosis (MS) with limited ambulatory ability, and its impact on motor function in an outpatient setting.

Design

Retrospective.

Setting

Tertiary referral center [Veterans Affairs (VA) Medical Center].

Participants

Veterans; 20 MS patients were prescribed dalfampridine (10 mg twice daily) due to their difficulty with walking based on patient and caregiver report and clinician impression of change in the ability to ambulate based on prior 10-meter (10M) and 2-minute walk tests (2MWTs).

Intervention

Not applicable.

Main Outcome Measures

The primary outcome measures were mean changes in walking speed (10M walk test), walking distance (2MWT), and Total Functional Independence Measure (TFIM). Improvement of >20 % in walking speed was indicated as a clinically meaningful change.

Results

Treatment with dalfampridine resulted in significant improvement in walking speed and endurance (p < 0.05). Walking speed increased by 33 % and walking endurance by 31 %, representing clinically meaningful improvement. This change was not influenced by change in muscle tone. This improvement in mobility was associated with a clinically significant change in motor function. Adverse effects, including insomnia, dizziness, and headache, were experienced by five patients who discontinued the medication after a minimum of 4 weeks.

Conclusion

Treatment with dalfampridine resulted in clinically relevant improvements in walking speed and endurance in MS patients with limited ambulation and helped improve their motor function.

Electronic supplementary material

The online version of this article (doi:10.1007/s40268-013-0020-x) contains supplementary material, which is available to authorized users.

Oral dalfampridine improves standing balance detected at static posturography in multiple sclerosis

We report a 14-week post-marketing experience on 20 patients with multiple sclerosis (MS) who started prolonged-release (PR) oral dalfampridine 10 mg twice daily according to European Medicine Agency criteria. They underwent serial static posturography assessments and the dizziness handicap inventory (DHI) to investigate whether PR dalfampridine could impact standing balance and self-reported perception of balance. The incidence of accidental falls per person per month was also recorded throughout the study. Eight (40%) patients, who had a relevant improvement in walking speed, were defined as treatment responders. They showed a significant improvement of standing balance (with respect to pretreatment assessment) when contrasted with 12 (60%) nonresponders (F [4,15] = 3.959, P = 0.027). No significant changes in DHI score, as well as in its functional, physical, and emotional subscales, were found in both responders and nonresponders at the end of study (all P values are ≥0.2). Treatment response did not affect the incidence of accidental falls. Future studies based on larger sample sizes, and with longer followup, are required to confirm the beneficial effect of PR dalfampridine on standing balance.

4-Aminopyridine for symptomatic treatment of multiple sclerosis: a systematic review

This systematic review summarizes the existing evidence on the effect of 4-aminopyridine (4-AP) as a symptomatic treatment of decreased walking capacity in patients with multiple sclerosis (MS) when administered as an immediate release compound and a slow release compound. It summarizes existing evidence on the basic mechanisms of 4-AP from experimental studies and evidence on the clinical use of the compound. A systematic literature search was conducted of the following databases: PubMed and EMBASE. Thirty-five studies were included in the review divided into 16 experimental studies, two clinical studies with paraclinical endpoints and 17 clinical studies with clinical endpoints. Animal studies show that 4-AP can improve impulse conduction through demyelinated lesions. In patients with MS this translates into improved walking speed and muscle strength of the lower extremities in a subset of patients at a level that is often of clinical relevance. Phase III trials demonstrate approximately 25% increase in walking speed in roughly 40% and improved muscle strength in the lower extremities. Furthermore, 4-AP might have an effect on other domains such as cognition, upper extremity function and bowel and bladder, but this warrants further investigation. Side effects are mainly mild to moderate, consisting primarily of paraesthesia, dizziness, nausea/vomiting, falls/balance disorders, insomnia, urinary tract infections and asthenia. Side effects are worse when administered intravenously and when administered as an immediate release compound. Serious adverse events are rarely seen in the marketed clinical dosages. In conclusion, 4-AP is easy and safe to use. Slow release 4-AP shows more robust clinical effects and a more beneficial side-effect profile than immediate release 4-AP.

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.

Pharmacokinetic profile of dalfampridine extended release: clinical relevance in patients with multiple sclerosis

BACKGROUND

In January 2010, dalfampridine extended release tablets (dalfampridine-ER [Ampyra *]; prolonged-, modified- or sustained-release fampridine [Fampyra †] in some countries), 10 mg to be administered twice daily approximately 12 hours apart, were approved by the US Food and Drug Administration. This was the first drug indicated to improve walking in patients with MS.

SCOPE

Publications describing the pharmacokinetics of dalfampridine-ER or the immediate release formulation were identified from a search of PubMed through June 2012 using the search terms 'dalfampridine OR fampridine OR 4-aminopyridine' AND 'pharmacokinetics' and were supplemented with unpublished studies made available by Acorda Therapeutics Inc.

FINDINGS

Pharmacokinetic studies show dose proportionality, with dalfampridine-ER having a more favorable profile than immediate-release dalfampridine. With twice-daily dosing of dalfampridine-ER, time to peak plasma concentration (3.2-3.9 hours) and apparent terminal plasma half-life (5.6-6.4 hours) are approximately twice those of immediate-release formulations, with comparable overall exposure and peak plasma concentrations (21.6 ng/mL) that were maintained at levels approximately 50% lower than immediate release. Steady state is achieved within 39 hours; pharmacokinetics are predictable based on single dosing. Trough plasma concentrations of 13-15 ng/mL are required to maintain efficacy. Renal excretion is predominantly as unchanged compound, and renal clearance in healthy individuals exceeds the glomerular filtration rate. Since dalfampridine-ER exposure increases with renal impairment, it is contraindicated in patients with moderate or severe impairment in the US, and in patients with any renal impairment in the European Union.

CONCLUSIONS

Dalfampridine-ER has low protein binding, is not a substrate for p-glycoprotein and does not affect CYP450 enzymes, suggesting a low potential for drug-drug interactions. Because of the narrow therapeutic range and risk of adverse events, including seizure, with increasing plasma concentrations, the recommended dose and regimen of dalfampridine-ER should not be exceeded and not be used with other dalfampridine formulations. A limitation of this review is that it includes some data that have not yet been published.

A randomised double-blind, cross-over trial of 4-aminopyridine for downbeat nystagmus--effects on slowphase eye velocity, postural stability, locomotion and symptoms

OBJECTIVE

The effects of 4-aminopyridine (4-AP) on downbeat nystagmus (DBN) were analysed in terms of slow-phase velocity (SPV), stance, locomotion, visual acuity (VA), patient satisfaction and side effects using standardised questionnaires.

METHODS

Twenty-seven patients with DBN received 5 mg 4-AP four times a day or placebo for 3 days and 10 mg 4-AP four times a day or placebo for 4 days. Recordings were done before the first, 60 min after the first and 60 min after the last drug administration.

RESULTS

SPV decreased from 2.42 deg/s at baseline to 1.38 deg/s with 5 mg 4-AP and to 2.03 deg/s with 10 mg 4-AP (p<0.05; post hoc: 5 mg 4-AP: p=0.04). The rate of responders was 57%. Increasing age correlated with a 4-AP-related decrease in SPV (p<0.05). Patients improved in the 'get-up-and-go test' with 4-AP (p<0.001; post hoc: 5 mg: p=0.025; 10 mg: p<0.001). Tandem-walk time (both p<0.01) and tandem-walk error (4-AP: p=0.054; placebo: p=0.059) improved under 4-AP and placebo. Posturography showed that some patients improved with the 5 mg 4-AP dose, particularly older patients. Near VA increased from 0.59 at baseline to 0.66 with 5 mg 4-AP (p<0.05). Patients with idiopathic DBN had the greatest benefit from 4-AP. There were no differences between 4-AP and placebo regarding patient satisfaction and side effects.

CONCLUSIONS

4-AP reduced SPV of DBN, improved near VA and some locomotor parameters. 4-AP is a useful medication for DBN syndrome, older patients in particular benefit from the effects of 5 mg 4-AP on nystagmus and postural stability.

Population pharmacokinetics and pharmacodynamics of dalfampridine-ER in healthy volunteers and in patients with multiple sclerosis

OBJECTIVE

Using data pooled from several studies of dalfampridine extended release (ER), a population pharmacokinetic model was developed for the purposes of characterizing the population pharmacokinetics and pharmacodynamics of dalfampridine-ER with respect to variability in pharmacokinetics, covariates affecting the pharmacokinetics, and whether the current therapeutic dosage represents an optimal dosage. Studies were conducted in healthy volunteers and multiple sclerosis (MS) patients over the course of development and registration of dalfampridine extended release tablets (dalfampridine-ER [Ampyra *]; prolonged-, modified- or sustained-release fampridine [Fampyra †] in some countries).

METHODS

The model used to best describe the population pharmacokinetics of dalfampridine-ER was an open, one-compartment model with first-order absorption, first-order elimination and an absorption lag time.

RESULTS

The population median estimated oral clearance was 36 L/h for a 50-year-old woman with a creatinine clearance of 105 mL/min and 42 L/h for a comparable man. The typical volume of distribution was 304 L for women and 403 L for men. The estimated absorption rate constant was 1.22 hours(-1) in the fasted state and 2.22 hours(-1) when given with food. The covariates identified as having a significant effect (p < 0.01) on model fit were food and gender on absorption rate, and gender, age and creatinine clearance on oral clearance. Only creatinine clearance and age are of clinical relevance. Concomitant medications did not affect any of the parameters in the model. Exposure-response relationships for both efficacy and safety were consistent with what has been observed in clinical trials. Limitations of this study include some reliance on unpublished data, and the limited effectiveness of the model for determining the likelihood of the efficacy and safety of dalfampridine-ER in clinical practice.

CONCLUSIONS

The approved therapeutic dosage regimen of dalfampridine-ER 10 mg twice daily was identified as the optimum dosing regimen based on model-predicted exposure response relationships for efficacy and adverse events. A limitation of this study is the limited effectiveness of the models used to predict long-term efficacy and safety of dalfampridine-ER in clinical use.

Recommendations for the use of prolonged-release fampridine in patients with multiple sclerosis (MS)

Prolonged-release fampridine (fampridine PR) is a potassium channel blocker that improves conductivity of signal on demyelinated axons in central nervous system. Fampridine PR has been approved to improve speed of walking in patients with multiple sclerosis. This statement provides a brief summary of data on fampridine PR and recommendations on practical use of the medication in clinical practice, prediction, and evaluation of response to treatment and patient management.

Dalfampridine improves walking speed, walking endurance, and community participation in veterans with multiple sclerosis: a longitudinal cohort study

BACKGROUND

In short-term trials, dalfampridine extended release (ER) improves walking in people with multiple sclerosis (MS). The tolerability and effects of dalfampridine-ER in clinical practice have not been reported.

OBJECTIVES

The objective of this paper is to determine the clinical tolerability and effects of dalfampridine on walking and community participation.

METHODS

All patients at the Portland VA Medical Center prescribed dalfampridine-ER over one year completed the Timed 25-Foot Walk (T25FW), Multiple Sclerosis Walking Scale-12 (MSWS-12), Two-Minute Timed Walk (2MTW), and Community Integration Questionnaire (CIQ) at baseline and follow-up clinic visits. Ongoing use and measures over one year were analyzed.

RESULTS

A total of 39 patients (mean age 56.5 years, mean disease duration 19.5 years, 82% male, 38% relapsing-remitting MS, 62% progressive MS) were prescribed dalfampridine-ER. Twenty-four (62%) continued to take dalfampridine-ER. At initial follow-up, all measures improved significantly from baseline (T25FW: -2.7 s, p = 0.004; 2MTW: 41 feet (ft), p = 0.002; MSWS12: -11, p < 0.001; CIQ: 1.2, p = 0.003). At one year, walking endurance and self-perceived walking were still significantly improved (2MTW: 33 ft, p = 0.03; MSWS-12: 5.9, p = 0.007).

CONCLUSIONS

Dalfampridine-ER was associated with short-term improvements in walking speed and community participation, and sustained improvements in walking endurance and self-perceived impact of MS on walking for one year. Our study supports the utility of this medication in late MS.

4-Aminopyridine ameliorates mobility but not disease course in an animal model of multiple sclerosis

Neuropathological changes following demyelination in multiple sclerosis (MS) lead to a reorganization of axolemmal channels that causes conduction changes including conduction failure. Pharmacological modulation of voltage-sensitive potassium channels (K(V)) has been found to improve conduction in experimentally induced demyelination and produces symptomatic improvement in MS patients. Here we used an animal model of autoimmune inflammatory neurodegeneration, namely experimental autoimmune encephalomyelitis (EAE), to test the influence of the K(V)-inhibitor 4-aminopyridine (4-AP) on various disease and immune parameters as well as mobility in MOG₃₅₋₅₅ immunized C57Bl/6 mice. We challenged the hypothesis that 4-AP exerts relevant immunomodulatory or neuroprotective properties. Neither prophylactic nor therapeutic treatment with 4-AP altered disease incidence or disease course of EAE. Histopathological signs of demyelination and neuronal damage as well as MRI imaging of brain volume changes were unaltered. While application of 4-AP significantly reduced the standing outward current of stimulated CD4(+) T cells compared to controls, it failed to impact intracellular calcium concentrations in these cells. Compatibly, KV channel inhibition neither influenced CD4(+) T cell effector functions (proliferation, IL17 or IFNγ production). Importantly however, despite equal disease severity scores 4-AP treated animals showed improved mobility as assessed by 2 independent methods, 1) foot print and 2) rotarod analysis (0.332 ± 0.03, n=7 versus 0.399 ± 0.08, n=14, p<0.001, respectively). Our data suggest that 4-AP while having no apparent immunomodulatory or direct neuroprotective effects, significantly ameliorates conduction abnormalities thereby improving gait and coordination. Improvement of mobility in this experimental model supports trial data and clinical experience with 4-AP in the symptomatic treatment of MS.

Assessing dalfampridine efficacy in the physician’s office

Dalfampridine (extended release 4-aminopyridine) is shown in three recent randomised controlled trials to improve walking speed in people with multiple sclerosis; however, the trial literature makes it clear that dalfampridine is effective in only a subset of patients. For the neurologist working in an everyday physician’s office, a key question arises: How to distinguish the few who experience a meaningful clinical benefit, from the many who do not? This question has not yet been adequately addressed in the available literature.

The use of aminopyridines in neurological disorders

Aminopyridines are members of a family of monoamino and diamino derivatives of pyridine, and their principal mechanism of action is dose-dependent blockade of voltage-gated potassium channels, in particular, fast voltage-gated potassium channels. To date, only 2 main broad-spectrum potassium channel blockers, 4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP), have been used as investigational new drugs in various neurological diseases. More recently, licensed versions of these compounds including dalfampridine extended release (Fampyra, Biogen Idec) for the improvement of walking in adult patients with multiple sclerosis, and amifampridine (Firdapse, Biomarin Europe Ltd) for the treatment of Lambert-Eaton myasthenic syndrome have been released, and the costs associated with using these new products highlights the importance of evaluating the clinically meaningful treatment effects of these drugs.The current review summarizes the evidence of aminopyridine use in neurological conditions and in particular presents a systematic review of all randomized trials of 3,4-DAP in Lambert-Eaton myasthenic syndrome to determine the efficacy of this treatment using meta-analysis of clinical and electrophysiological end points.

Dalfampridine improves sensorimotor function in rats with chronic deficits after middle cerebral artery occlusion

BACKGROUND AND PURPOSE

Stroke survivors often have permanent deficits that are only partially addressed by physical therapy. This study evaluated the effects of dalfampridine, a potassium channel blocker, on persistent sensorimotor deficits in rats with treatment initiated 4 or 8 weeks after stroke.

METHODS

Rats underwent permanent middle cerebral artery occlusion. Sensorimotor function was measured using limb-placing and body-swing symmetry tests, which normally show a partial recovery from initial deficits that plateaus ≈4 weeks after permanent middle cerebral artery occlusion. Dalfampridine was administered starting at 4 or 8 weeks after permanent middle cerebral artery occlusion in 2 blinded, vehicle-controlled studies. Plasma samples were collected and brain tissue was processed for histologic assessment.

RESULTS

Dalfampridine treatment (0.5-2.0 mg/kg) improved forelimb- and hindlimb-placing responses and body-swing symmetry in a reversible and dose-dependent manner. Plasma dalfampridine concentrations correlated with dose. Brain infarct volumes showed no differences between treatment groups.

CONCLUSIONS

Dalfampridine improves sensorimotor function in the rat permanent middle cerebral artery occlusion model. Dalfampridine extended-release tablets (prolonged release fampridine outside the United States) are used to improve walking in patients with multiple sclerosis, and these preclinical data provide a strong rationale for examining the potential of dalfampridine to treat chronic stable deficits in stroke patients.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01605825.

Effects of dalfampridine and its metabolites on cloned human potassium channels Kv 1.1, Kv 1.2, and Kv 1.4 expressed in human embryonic kidney cells

BACKGROUND

Dalfampridine (4-aminopyridine; 4-AP) is a potassium channel blocker that has been available in the United States as a treatment to improve walking in patients with multiple sclerosis. 4-AP is well-characterized in vitro with regard to inhibition of neuronal potassium channels, but the potential contribution of its metabolites to clinical activity has not been determined. This study evaluated the concentration-response of 4-AP and its two primary metabolites, 3-hydroxy-4-aminopyridine and 3-hydroxy-4-aminopyridine sulfate, for inhibition of the potassium channels Kv 1.1, Kv 1.2, and Kv 1.4, which are considered candidates for mediating effects of 4-AP on action potential conduction because of their presence in axonal membranes.

METHODS

Stable transfection of cDNA for Kv 1.1, Kv 1.2, and Kv 1.4 was performed into HEK293 cells, and colonies of cells containing each channel were selected and maintained under appropriate cell culture conditions. Electrophysiological measurements were performed using a patch-clamp technique in at least three cells for each concentration (50, 500, 5000, and 50,000 μM) of 4-AP and the two metabolites, with each cell acting as its own control. Concentration-response curves were constructed for 4-AP and each metabolite. Data were analyzed using nonlinear least-squares fit, and concentrations inhibiting the channels by 50% (IC50) were estimated.

RESULTS

4-AP induced similar concentration-dependent inhibition profiles of all three potassium channels, resulting in a narrow range of IC50 values across channels (242 µM to 399 µM). Across the three channels, the IC50 values of 3-hydroxy-4-aminopyridine and 3-hydroxy-4-aminopyridine sulfate were 1-2 orders of magnitude higher (less potent) than those of 4-AP.

CONCLUSIONS

3-Hydroxy-4-aminopyridine and 3-hydroxy-4-aminopyridine sulfate demonstrated low in vitro potency for Kv 1.1, Kv 1.2, and Kv 1.4 inhibition, suggesting that these metabolites are unlikely to contribute to the positive pharmacodynamic effects of 4-AP. A limitation of this study is that while the metabolites were substantially less active at these representative potassium channels in vitro, the untested possibility exists that they may be active at one or more of the many other channel types that occur in vivo.

Enhancing neural transmission in multiple sclerosis (4-aminopyridine therapy)

Enhancing neural transmission by improving axonal conduction and synaptic neurotransmitter release is a novel strategy to improve symptoms in multiple sclerosis. Dalfampridine (4-aminopyridine extended-release) is a first-in-class medication that targets the damaged nervous system through blockage of voltage-gated potassium channels. Through a series of clinical trials, dalfampridine (dosed at 10 mg twice daily) has been found to improve walking speed by approximately 25 % on average in one third of individuals with multiple sclerosis regardless of disease stage. Furthermore, it significantly improves patients' perception of their ambulatory disability and may improve lower extremity strength. Given the mechanism of action, the most serious adverse effect is its pro-convulsant property, which occurs more frequently at high serum concentrations. The most common adverse events include increased falls, urinary tract infections, dizziness, insomnia, and headaches. Despite these potential side-effects, the vast majority of individuals who derive benefit continue on the treatment. The exact mechanism of action is uncertain, as is the reason for response variability. The medication serves as proof-of-concept that targeting axonal transmission can improve disability in multiple sclerosis.

Dalfampridine extended release tablets: 1 year of postmarketing safety experience in the US

BACKGROUND

Dalfampridine extended release tablets (dalfampridine-ER; prolonged-, modified, or sustained-release fampridine in some countries) were approved in the US to improve walking in patients with multiple sclerosis, as demonstrated by improvement in walking speed. Postmarketing safety experience is available from exposure of approximately 46,000 patients in the US from product approval through March 2011.

OBJECTIVE

To provide a descriptive analysis of all spontaneously reported postmarketing adverse events (AEs) for dalfampridine-ER since product launch.

METHODS

AE data were extracted from the safety database from product launch through March 31, 2011; AEs were classified using the Medical Dictionary for Regulatory Activities. Seizure cases were reviewed for patient demographics, time to event from treatment onset, and presence of additional risk factors.

RESULTS

THE MOST FREQUENTLY REPORTED POSTMARKETING AES WERE SIMILAR TO THOSE REPORTED DURING CLINICAL DEVELOPMENT: dizziness, insomnia, balance disorder, headache, nausea, urinary tract infection, asthenia, and back pain (all included in US product labeling). New clinically significant findings are related to lack of efficacy and inappropriate dosing. Of the approximately 46,000 patients exposed, 85 seizures were reported (∼5.4/1000 patient-years), of which 82 were reported or confirmed by a health care practitioner (∼5.2/1000 patient-years). Beyond the intrinsic multiple sclerosis-related seizure risk, more than half of the 85 cases (62%) had an additional potential risk factor for seizure including a previous history of convulsions, renal impairment, incorrect dosing, or use of concurrent medications with a labeled seizure risk. Duration of treatment prior to the seizure ranged from one dose to 365 days; 26/85 (31%) patients suffered a seizure within a week of starting treatment.

CONCLUSION

Spontaneous safety data from the US postmarketing experience were consistent with the safety profile seen during clinical development. Although first-year seizure incidence was not substantially different from that observed in dalfampridine-ER clinical trials, patients should be monitored for concomitant use of drugs that lower seizure threshold.

Sustained-release fampridine and the role of ion channel dysfunction in multiple sclerosis

Ion channel dysfunction is an important mechanism that contributes to functional disability and axonal degeneration in multiple sclerosis (MS). Recent studies have revealed that there are complex rearrangements of voltage-gated Na+ channels that occur with acute brain inflammation in MS, with up-regulation of primitive Na+ channel isoforms such as Nav 1.2 during acute inflammation. While these changes may help support neural conduction, increased expression of ‘persistent’ Na+ conductances and altered function of the Na+/K+ pump may contribute to axonal degeneration in MS. Increased expression of K+ channels due to demyelination has also been considered as a contributing factor to conduction failure in MS. Recent phase II and phase III clinical trials have demonstrated improvements in walking speed in patients receiving fampridine SR, a K+ channel blocker. This medication appears to be well-tolerated with a low risk of serious adverse events and provides benefits in both relapsing and progressive forms of MS.

4-aminopyridine toxicity: a case report and review of the literature

INTRODUCTION

4-Aminopyridine (4-AP) selectively blocks voltage-gated potassium channels, prolongs the action potential, increases calcium influx, and subsequently, enhances interneuronal and neuromuscular synaptic transmission. This medication has been studied and used in many disease processes hallmarked by poor neuronal transmission in both the central and peripheral nervous systems including: multiple sclerosis (MS), spinal cord injuries (SCI), botulism, Lambert-Eaton syndrome, and myasthenia gravis. It has also been postulated as a potential treatment of verapamil toxicity and reversal agent for anesthesia-induced neuromuscular blockade. To date, there have been limited reports of either intentional or accidental 4-AP toxicity in humans. Both a case of a patient with 4-AP toxicity and review of the literature are discussed, highlighting commonalities observed in overdose.

CASE REPORT

A 37-year-old man with progressive MS presented with diaphoresis, delirium, agitation, and choreathetoid movements after a presumed 4-AP overdose. 4-AP concentration at 6 h was 140 ng/mL. With aggressive benzodiazepine administration and intubation, he recovered uneventfully.

DISCUSSION

The commonalities associated with 4-AP toxicity conforms to what is known about its mechanism of action combining cholinergic features including diaphoresis, altered mental status, and seizures with dopamine-related movement abnormalities including tremor, choreoathetosis, and dystonia. Management of patients poisoned by 4-AP centers around good supportive care with definitive airway management and controlling CNS hyperexcitability aggressively with gamma-aminobutyric acid agonist agents. Adjunctive use of dopamine antagonists for extrapyramidal effects after sedation is a treatment possibility. As 4-aminopyridine recently received Federal Drug Administration approval for the treatment of ambulation in patients with MS, physicians should be keenly aware of its presentation, mechanism of action, and management in overdose.

Extended-release dalfampridine in the management of multiple-sclerosis-related walking impairment

Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system that causes neurological impairment in young adults. As part of the disease, ambulation remains one of the most disabling features of multiple sclerosis. Extended-release dalfampridine is a long-acting form of 4-aminopyridine that has been shown in two phase III trials to increase ambulation speed in a subset of patients with multiple sclerosis (timed walk responders). The primary endpoint of these studies was 'responder status', analyzing difference in the proportion of timed walk responders between extended-release dalfampridine and placebo groups. Extended-release dalfampridine exerts its effects by inhibiting voltage-activated K(+) channels and has been previously demonstrated to improve action potential propagation in demyelinated nerve fibers in vitro. Side effects of extended-release dalfampridine include increased urinary tract infections, insomnia, headache, asthenia, dizziness, back pain, and paresthesias. Rare seizure events are also reported on the approved dose of 10 mg every 12 h. In this review we will summarize the results of key phase II and phase III trials of extended-release dalfampridine, its safety, and potential use in patients with multiple sclerosis.

Dalfampridine: A Medication to Improve Walking in Patients with Multiple Sclerosis

OBJECTIVE:

To review the pharmacology, pharmacokinetics, efficacy, and safety of dalfampridine.

DATA SOURCES:

A search of PubMed (1966-March 2012) was conducted using the words dalfampridine and Ampyra. Bibliographies of retrieved articles were reviewed to identify additional references.

STUDY SELECTION AND DATA EXTRACTION:

All identified studies published in English involving the efficacy and safety of dalfampridine were reviewed.

DATA SYNTHESIS:

Dalfampridine (Ampyra) is a broad-spectrum potassium channel blocker that is indicated as a treatment to improve walking in patients with multiple sclerosis (MS). Dalfampridine is the only medication approved for this indication. Efficacy has been demonstrated in 2 Phase 3 trials involving patients with MS. Dalfampridine 10 mg twice daily improved walking, as shown by a higher proportion of timed walk responders in the dalfampridine-treated group (42.9% and 35%) versus the placebo-treated group (9.3% and 8%) during the 2 studies (p < 0.001). The maximum recommended dose of dalfampridine is 10 mg twice daily; higher doses are associated with an increased risk of seizures. At doses greater than 10 mg twice daily, the frequency of other adverse reactions and discontinuations was greater and showed no additional benefit. The average wholesale price of a 10-mg dalfampridine tablet is $21.12, which would make a 1-month supply of therapy cost $1267.20.

CONCLUSIONS:

In clinical trials, dalfampridine improved walking speed in approximately one third of patients with MS. The risk of seizures appears to be dose-related and the incidence is low at doses of 10 mg twice daily. Because of the cost, dalfampridine should be reserved for patients who meet criteria for the drug and continued only if they have an adequate response.

Walking impairment in patients with multiple sclerosis - a new therapeutic approach and clinical potential of dalfampridine extended release tablets

Walking impairment is a clinical hallmark of multiple sclerosis (MS) that has been under-recognized as a therapeutic target for pharmacologic intervention. The development and approval of dalfampridine extended release tablets (dalfampridine-ER; known as prolonged-, modified, or sustained-release fampridine outside the USA), 10 mg taken twice daily, to improve walking in patients with MS, fills a previously unmet need. In three randomized, double-blind, placebo-controlled trials, dalfampridine-ER improved walking speed in approximately one-third (37%) of treated patients, and average walking speed on therapy among these responders improved by approximately 25% relative to baseline. Walking-speed improvement among responders was clinically significant, as determined by a statistically significant improvement in the patient-reported 12-item Multiple Sclerosis Walking Scale. Long-term extension studies indicate that responders were able to maintain benefits, compared with nonresponders over prolonged periods of treatment. Dalfampridine-ER was generally well tolerated. Dizziness, insomnia, balance disorder, headache, nausea, urinary tract infection, and asthenia were the most common adverse events. Although the incidence of seizures appeared to be dose related, among patients treated with dalfampridine-ER in the three trials, the rate of seizures was 0.25%. These efficacy and safety data suggest that dalfampridine-ER can be a useful and clinically relevant addition to the pharmacologic armamentarium for the management of MS symptoms and disabilities. Because of its narrow therapeutic index and potential for seizures, it is especially important in the clinical setting to adhere to the dosing recommended in the approved labels.

Dalfampridine: a new agent for symptomatic management of multiple sclerosis

PURPOSE The pharmacology, pharmacokinetics, clinical efficacy, safety, dosage, and place in therapy of dalfampridine are reviewed. SUMMARY Dalfampridine is a novel drug with a unique mechanism for the symptomatic management of multiple sclerosis (MS) among all classifications. Dalfampridine was approved in January 2010 to improve walking for patients with MS. Dalfampridine blocks potassium channels on demyelinated neurons and allows normal electrical conduction, thus improving locomotor difficulty. Dalfampridine is rapidly absorbed after oral administration, reaching its peak plasma concentration in 1.3 hours. Approximately 95.9% of dalfampridine and its metabolites (3-hydroxy-4-aminopyridine and 3- hydroxy-4-aminopyridine sulfate) is excreted in the urine. Dalfampridine is not an inhibitor or inducer of a major cytochrome P-450 isoenzyme; therefore, the potential for drug-drug interactions is minimal. Clinical studies have shown dalfampridine to improve walking speed. The dosage of dalfampridine varied in clinical trials, but the recommended dosage is 10 mg orally twice daily. Dalfampridine is not appropriate for patients with seizures or moderate-to-severe renal impairment. Phase III studies found that extended-release fampridine 10 mg twice daily is well tolerated. The most frequent adverse events reported in dalfampridine clinical trials were insomnia, dizziness, headache, nausea, and weakness. The Food and Drug Administration has required the manufacturer to have a risk evaluation and mitigation strategy for dalfampridine. Ongoing trials will determine the long-term benefit of dalfampridine. CONCLUSION Dalfampridine is a potassium channel blocker that has demonstrated efficacy for improving the symptoms of MS. Several studies have demonstrated increased walking speed in patients, though high doses should be avoided due to the risk of seizures.

The safety profile of dalfampridine extended release in multiple sclerosis clinical trials

BACKGROUND

Dalfampridine (fampridine outside the United States) is a broad-spectrum potassium channel blocker. Dalfampridine extended-release tablets have been approved by the US Food and Drug Administration to improve walking in patients with multiple sclerosis (MS).

OBJECTIVE

The objective of this article is to review the safety profile of dalfampridine extended-release tablets with respect to its expected use in patients with MS.

METHODS

We reviewed published data relevant to patient safety profiles based on searches of articles in PubMed published up to December 31, 2010, using the search terms fampridine OR dalfampridine OR 4-aminopyridine AND (multiple sclerosis) in combination with toxicity, safety, clinical trial, pharmacokinetics, and seizures. These searches were supplemented with data derived from the approved package insert and relevant sections of the New Drug Application (22-250) as submitted to the US Food and Drug Administration.

RESULTS

The literature searches returned 58 unique citations, of which 26 were considered relevant for characterizing the safety profile of dalfampridine; excluded citations were as follows: reviews (19), evaluation of 3,4-diaminopyridine (4), intravenous dosing (2), inadequate information on patient doses (2), preclinical models (2), and "other" (3). Dalfampridine is nearly completely (approximately 96%) eliminated unchanged in urine, with limited transformation to 2 inactive metabolites and low risk for interaction with drugs metabolized by hepatic P450 cytochromes. However, in patients with renal impairment (creatinine clearance [CrCl], ≤80 mL/min), mean peak plasma concentrations were 68%-101% higher and apparent clearance was 43%-73% lower relative to those without impairment, precluding dalfampridine use in patients with moderate (CrCl, 30-50 mL/min) or severe renal impairment (CrCl, <30 mL/min). Dalfampridine has a narrow therapeutic range. At the therapeutic dose of 10 mg twice daily, adverse events were generally mild to moderate and, consistent with the mechanism of action of dalfampridine, were primarily related to stimulatory effects on the nervous system. A thorough QT study suggested a low risk of induction of QT prolongation and associated cardiac arrhythmias in healthy individuals at therapeutic (10 mg, twice daily) or supratherapeutic (30 mg, twice daily) doses. Although the incidence of seizures was dose related, data from the clinical trials of dalfampridine extended-release tablets suggest that the risk of seizure at the therapeutic dose, in patients with no history of seizure, is not likely to be higher than background rates in MS.

CONCLUSION

In patients with MS, dalfampridine has a narrow therapeutic range but an acceptable safety profile when used at the therapeutic dose of 10 mg twice daily.

Body-worn motion sensors detect balance and gait deficits in people with multiple sclerosis who have normal walking speed

While balance and gait limitations are hallmarks of multiple sclerosis (MS), standard stopwatch-timed measures practical for use in the clinic are insensitive in minimally affected patients. This prevents early detection and intervention for mobility problems. The study sought to determine if body-worn sensors could detect differences in balance and gait between people with MS with normal walking speeds and healthy controls. Thirty-one MS and twenty-eight age- and sex-matched control subjects were tested using body-worn sensors both during quiet stance and gait (Timed Up and Go test, TUG). Results were compared to stopwatch-timed measures. Stopwatch durations of the TUG and Timed 25 Foot Walk tests were not significantly different between groups. However, during quiet stance with eyes closed, people with MS had significantly greater sway acceleration amplitude than controls (p=0.02). During gait, people with MS had greater trunk angular range of motion in roll (medio-lateral flexion, p=0.017) and yaw (axial rotation, p=0.026) planes. Turning duration through 180° was also longer in MS (p=0.031). Thus, body-worn motion sensors detected mobility differences between MS and healthy controls when traditional timed tests could not. This portable technology provides objective and quantitative mobility data previously not obtainable in the clinic, and may prove a useful outcome measure for early mobility changes in MS.

Effect of food on the single-dose pharmacokinetics and tolerability of dalfampridine extended-release tablets in healthy volunteers

PURPOSE

The pharmacokinetics, bioavailability, and tolerability of dalfampridine extended-release tablets in healthy adults under fed and fasted conditions were evaluated.

METHODS

The study participants (n = 30) were randomly assigned to receive one 10-mg dalfampridine tablet in a fasted condition (no food for 10-12 hours) or a fed condition (after a high-fat meal); after a seven-day washout period, participants received the same dalfampridine dosage under the converse condition. The endpoints were the maximum plasma drug concentration (C(max)) and areas under the plasma-concentration curve (AUC) for 24-hour exposure (AUC(0-24)) and total exposure (AUC(0-∞)). A 90% two-sided confidence interval (CI) within predefined limits for the fed:fasted ratio of the geometric mean values was used as the standard for determining the absence of a significant food effect.

RESULTS

Among the participants who received both treatments (n = 28), food intake was associated with a 23% increase in the log-transformed geometric mean C(max) of dalfampridine (p ≤ 0.10) but no significant change in mean AUC values. Eight (26.7%) of the study participants reported a total of 13 adverse events (AEs), of which only dizziness and upper abdominal pain occurred in more than one participant; all AEs were of mild-to-moderate severity.

CONCLUSION

When a single 10-mg dose of dalfampridine was given to healthy volunteers after a high-fat meal, a significant increase in C(max) was observed. However, overall differences in dalfampridine pharmacokinetics when the drug was administered to participants under fasting and fed conditions did not exceed predefined limits, indicating that the extended-release formulation may be taken without regard to meals.

Management options in multiple sclerosis-associated fatigue

INTRODUCTION

Multiple sclerosis (MS) is a chronic, inflammatory, autoimmune disease of the CNS. Its characteristic early clinical course includes exacerbations and remissions of neurologic disability. Fatigue is one of the most common symptoms of MS and is associated with a reduced quality of life; it is described as the worst symptom of the disease by 50 - 60% of patients. Yet, due to limitations of available evidence, current therapeutic approaches for treating fatigue are based mainly on preliminary studies and expert consensus.

AREAS COVERED

This review summarizes current knowledge on the physiopathology, diagnosis and therapeutic options for MS-associated fatigue, including both pharmacological and non-pharmacological strategies.

EXPERT OPINION

Large, rigorously designed trials can provide more reliable results on the efficacy of interventions for fatigue, their functional impact on everyday activities and patient quality of life. Future research should also address a better understanding of the physiopathologic mechanisms of fatigue and the development and validation of objective assessment tools to be used together with patient self-ratings.

Therapeutics for multiple sclerosis symptoms

Symptoms management in multiple sclerosis is an integral part of its care. Accurate assessment and addressing the different symptoms provides increased quality of life among patients with multiple sclerosis. Multiple sclerosis symptoms may be identified as primary, secondary, or tertiary symptoms. Primary symptoms, such as weakness, sensory loss, and ataxia, are directly related to demyelination and axonal loss. Secondary symptoms, such as urinary tract infections as a result of urinary retention, are a result of the primary symptoms. Tertiary symptoms, such as reactive depression or social isolation, are a result of the social and psychological consequences of the disease. Common multiple sclerosis symptoms include fatigue and weakness; decreased balance, spasticity and gait problems; depression and cognitive issues; bladder, bowel, and sexual deficits; visual and sensory loss; and neuropathic pain. Less-common symptoms include dysarthria and dysphagia, vertigo, and tremors. Rare symptoms in multiple sclerosis include seizures, hearing loss, and paralysis. Symptom management includes nonpharmacological methods, such as rehabilitation and psychosocial support, and pharmacological methods, ie, medications and surgical procedures. The keys to symptom management are awareness, knowledge, and coordination of care. Symptoms have to be recognized and management needs to be individualized. Multiple sclerosis therapeutics include nonpharmacological strategies that consist of lifestyle modifications, rehabilitation, social support, counseling, and pharmacological agents or surgical procedures. The goal is vigilant management to improve quality of life and promote realistic expectations and hope.

Symptomatic management in multiple sclerosis

The development of immunomodulatory therapies for multiple sclerosis (MS) has had significant impact in altering the natural history of the disease. Although these agents reduce relapse rate and MRI-associated disease activity, they are only partially effective and do not ameliorate irreversible axonal injury, which produces much of the symptomatic burden of MS. Treatment of MS-associated symptoms remains an essential cornerstone of comprehensive care of patients with MS and, arguably, more favorably enhances quality of life than do the disease-modifying medications. This article reviews strategies of symptom management in patients with MS.

Treatment of walking impairment in multiple sclerosis with dalfampridine

Potassium channel blockade has long been considered a potential therapeutic strategy for treatment of multiple sclerosis (MS) based on the pathophysiology of demyelinated axons. Dalfampridine, which is also known as fampridine or 4-aminopyridine (4-AP), is the potassium channel blocker that has been studied most extensively in MS and other demyelinating neurologic disorders. An extended-release formulation of dalfampridine was recently approved by the US Food and Drug Administration to improve walking in patients with MS. In randomized, double-blind, placebo-controlled trials, with dalfampridine extended release tablets 10 mg taken twice daily, about 12 h apart, walking speed was improved in approximately one-third of treated patients; in these patients, average walking speed on therapy was about 25% above baseline. This improvement was clinically meaningful as assessed by concurrent measurement of patient-reported severity of walking-related disability. Dalfampridine extended release tablets were generally well tolerated, with a range of adverse effects that appear to be related to increases in central nervous system excitation. There is a dose-dependent increase in the occurrence of seizures at doses higher than the recommended 10 mg twice daily.

A randomized trial of 4-aminopyridine in EA2 and related familial episodic ataxias

OBJECTIVE

The therapeutic effects of 4-aminopyridine (4AP) were investigated in a randomized, double-blind, crossover trial in 10 subjects with familial episodic ataxia with nystagmus.

METHODS

After randomization, placebo or 4AP (5 mg 3 times daily) was administered for 2 3-month-long treatment periods separated by a 1-month-long washout period. The primary outcome measure was the number of ataxia attacks per month; the secondary outcome measures were the attack duration and patient-reported quality of life (Vestibular Disorders Activities of Daily Living Scale [VDADL]). Nonparametric tests and a random-effects model were used for statistical analysis.

RESULTS

The diagnosis of episodic ataxia type 2 (EA2) was genetically confirmed in 7 subjects. Patients receiving placebo had a median monthly attack frequency of 6.50, whereas patients taking 4AP had a frequency of 1.65 (p = 0.03). Median monthly attack duration decreased from 13.65 hours with placebo to 4.45 hours with 4AP (p = 0.08). The VDADL score decreased from 6.00 to 1.50 (p = 0.02). 4AP was well-tolerated.

CONCLUSIONS

This controlled trial on EA2 and familial episodic ataxia with nystagmus demonstrated that 4AP decreases attack frequency and improves quality of life.

LEVEL OF EVIDENCE

This crossover study provides Class II evidence that 4AP decreases attack frequency and improves the patient-reported quality of life in patients with episodic ataxia and related familial ataxias.