Rufinamide: a novel broad-spectrum antiepileptic drug

Advances in anti-epileptic drug testing

In the past twenty-one years, 17 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are clobazam, ezogabine (retigabine), eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. Therapeutic drug monitoring is often used in the clinical dosing of the newer anti-epileptic drugs. The drugs with the best justifications for drug monitoring are lamotrigine, levetiracetam, oxcarbazepine, stiripentol, and zonisamide. Perampanel, stiripentol and tiagabine are strongly bound to serum proteins and are candidates for monitoring of the free drug fractions. Alternative specimens for therapeutic drug monitoring are saliva and dried blood spots. Therapeutic drug monitoring of the new antiepileptic drugs is discussed here for managing patients with epilepsy.

Stable dosages of clobazam for Lennox-Gastaut syndrome are associated with sustained drop-seizure and total-seizure improvements over 3 years

Objective

To determine long-term safety and efficacy of adjunctive clobazam for patients with Lennox-Gastaut syndrome (LGS).

Methods

Eligible patients from two randomized controlled trials (Phase II OV-1002 and Phase III OV-1012) were able to enroll in open-label extension (OLE) study OV-1004 beginning in December 2005 and received clobazam until they discontinued (mandatory at 2 years for patients outside the United States) or until study completion in March 2012. Patients in the United States could have received clobazam for 6 years before it became commercially available. Efficacy assessments included changes in rates of drop seizures and total seizures, responder rates (≥50%, ≥75%, or 100% decreases in seizure frequency vs. baseline), sustained efficacy over time, concomitant antiepileptic drug (AED) use, and global evaluations. Safety assessments included exposure to clobazam, laboratory assessments, physical and neurologic examinations, vital sign monitoring, electrocardiography monitoring, and adverse event reporting.

Results

Of 267 patients who enrolled in the OLE, 188 (70%) completed the trial. Two hundred seven patients were from the United States, which was the only country in which patients could be treated with clobazam for >2 years. Forty-four patients were treated with clobazam for 5 years, and 11 for 6 years. Because of the low number of Year 6 patients, this group is not reported separately. Improvements in baseline seizure rates were very stable over the course of the study, with a median 85% decrease in drop seizures at Year 1, 87% at Year 2, 92% at Year 3, 97% at Year 4, and a 91% decrease for patients who had reached Year 5. Similar results were observed for total seizures (79% decrease at both Years 1 and 2, 82% decrease at Year 3, 75% decrease at Year 4, and 85% decrease at Year 5). Responder rates were also stable for the duration of the trial. Of patients who had achieved a ≥50% decrease in median drop-seizure frequency from baseline to Month 3, 86% still had that degree of drop-seizure reduction at Year 3 (and 14% lost their initial responses), and 47% were drop-seizure–free. Most patients who had achieved drop-seizure freedom in the original controlled trials remained drop-seizure–free in the OLE. Based on parents' and physicians' ratings of global evaluations, 80% of patients were “very much improved” or “much improved” after 3 years. Of the 43 patients with concomitant AED data who were treated for 5 years, 30% increased, 19% decreased, and 51% had no change in numbers of AEDs versus their Week 4 regimens. The mean modal clobazam dosage was 0.90 mg/kg/day at Year 1 and 0.97 mg/kg/day at Year 5, suggesting that study patients did not need significant increases in dosage over time. The safety profile was what would be expected for clobazam for LGS patients over a 5-year span, and no new safety concerns developed over time.

Significance

In this largest and longest-running trial in LGS, adjunctive clobazam sustained seizure freedom and substantial seizure improvements at stable dosages through 3 years of therapy in this difficult- to-treat patient population.

Therapeutic drug monitoring of antiepileptic drugs by use of saliva

Blood (serum/plasma) antiepileptic drug (AED) therapeutic drug monitoring (TDM) has proven to be an invaluable surrogate marker for individualizing and optimizing the drug management of patients with epilepsy. Since 1989, there has been an exponential increase in AEDs with 23 currently licensed for clinical use, and recently, there has been renewed and extensive interest in the use of saliva as an alternative matrix for AED TDM. The advantages of saliva include the fact that for many AEDs it reflects the free (pharmacologically active) concentration in serum; it is readily sampled, can be sampled repetitively, and sampling is noninvasive; does not require the expertise of a phlebotomist; and is preferred by many patients, particularly children and the elderly. For each AED, this review summarizes the key pharmacokinetic characteristics relevant to the practice of TDM, discusses the use of other biological matrices with particular emphasis on saliva and the evidence that saliva concentration reflects those in serum. Also discussed are the indications for salivary AED TDM, the key factors to consider when saliva sampling is to be undertaken, and finally, a practical protocol is described so as to enable AED TDM to be applied optimally and effectively in the clinical setting. Overall, there is compelling evidence that salivary TDM can be usefully applied so as to optimize the treatment of epilepsy with carbamazepine, clobazam, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, phenobarbital, phenytoin, primidone, topiramate, and zonisamide. Salivary TDM of valproic acid is probably not helpful, whereas for clonazepam, eslicarbazepine acetate, felbamate, pregabalin, retigabine, rufinamide, stiripentol, tiagabine, and vigabatrin, the data are sparse or nonexistent.

First long-term experience with the orphan drug rufinamide in children with myoclonic-astatic epilepsy (Doose syndrome)

INTRODUCTION

We evaluated the long-term efficacy and tolerability of the orphan drug rufinamide (RUF) in children with pharmacoresistant myoclonic-astatic epilepsy (MAE, Doose syndrome).

METHODS

This was a retrospective European multicenter study on eight patients who had started an intention-to-treat trial of RUF between July 2007 and June 2010. Clinical information was collected via questionnaire. Responder rate was defined as reduction of seizure frequency ≥50% in comparison to four weeks before starting RUF. Maximum follow-up was eighteen months.

RESULTS

Responder rates were 7/8 patients after 3 months, 6/8 patients after 6 months and 5/8 patients after 12 months. RUF seemed particularly effective in the prevention of myoclonic-astatic seizures (comparable with drop attacks in Lennox-Gastaut-Syndrome, for which RUF is particularly effective). Some loss of efficacy was noticed in the long-term observation. Side-effects occurred in two patients. Seizure aggravation was not observed.

CONCLUSION

RUF seems to be a promising therapeutic option in children with MAE. Further studies are warranted to confirm these first observations.

Drug-induced QT-interval shortening following antiepileptic treatment with oral rufinamide

BACKGROUND

The arrhythmogenic potential of short QT intervals has recently been highlighted in patients with a short QT syndrome. Drug-induced QT-interval prolongation is a known risk factor for ventricular tachyarrhythmias. However, reports on drug-induced QT-interval shortening are rare and proarrhythmic effects remain unclear.

OBJECTIVE

Recently, rufinamide, a new antiepileptic drug for the add-on treatment of Lennox-Gastaut syndrome, was approved in the European Union and the United States. Initial trials showed drug-induced QT-interval shortening. The aim of our study was to evaluate the effects of rufinamide on QT intervals in patients with difficult-to-treat epilepsies.

METHODS

Nineteen consecutive patients with Lennox-Gastaut syndrome and other epilepsy syndromes were included (n = 12 men; mean age 41 ± 12 years). QRS, QT, and T(peak)-T(end) intervals were analyzed before and during rufinamide treatment.

RESULTS

The mean QT interval shortened significantly following rufinamide administration (QT interval 349 ± 23 ms vs 327 ± 17 ms; corrected QT interval 402 ± 22 ms vs 382 ± 16 ms; P = .002). T(peak)-T(end) intervals were 79 ± 17 ms before and 70 ± 20 ms on treatment (P = .07). The mean reduction of the corrected QT interval was 20 ± 18 ms. During follow-up (3.04 ± 1.09 years), no adverse events including symptomatic cardiac arrhythmias or sudden cardiac deaths were observed.

CONCLUSION

QTc-interval shortening following oral rufinamide administration in a small patient group was not associated with significant clinical adverse effects. These observations notwithstanding, the ability of rufinamide to significantly shorten the QT interval portends a potential arrhythmogenic risk that may best be guarded against by periodic electrocardiographic recordings.

Pharmacokinetics of oral rufinamide in dogs

The objective of this study was to determine the pharmacokinetic properties and short-term adverse effect profile of single-dose oral rufinamide in healthy dogs. Six healthy adult dogs were included in the study. The pharmacokinetics of rufinamide were calculated following administration of a single mean oral dose of 20.0 mg/kg (range 18.6-20.8 mg/kg). Plasma rufinamide concentrations were determined using high-performance liquid chromatography, and pharmacokinetic data were analyzed using commercial software. No adverse effects were observed. The mean terminal half-life was 9.86 ± 4.77 h. The mean maximum plasma concentration was 19.6 ± 5.8 μg/mL, and the mean time to maximum plasma concentration was 9.33 ± 4.68 h. Mean clearance was 1.45 ± 0.70 L/h. The area under the curve (to infinity) was 411 ± 176 μg · h/mL. Results of this study suggest that rufinamide given orally at 20 mg/kg every 12 h in healthy dogs should result in a plasma concentration and half-life sufficient to achieve the therapeutic level extrapolated from humans without short-term adverse effects. Further investigation into the efficacy and long-term safety of rufinamide in the treatment of canine epilepsy is warranted.

Serum concentrations of rufinamide in children and adults with epilepsy: the influence of dose, age, and comedication

Rufinamide (RUF) is an orphan drug for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in persons aged 4 years and older. Several studies have investigated the pharmaconkinetics of RUF, but information about interactions is still limited and the results are in part inconsistent. The aim of our study was to analyze the effect of age, gender, daily RUF dose per body weight (mg/kg), valproic acid (VPA), and enzyme-inducing antiepileptic drugs (EIAEDs) on RUF concentration-to-dose ratio (RUF serum concentration/RUF dose per body weight), RUF clearance (RUF dose/RUF serum concentration), and RUF trough concentrations. Different statistical methods were used to evaluate 292 blood samples from 119 patients who fulfilled the inclusion criteria. In summary, the results using generalized estimating equation regression models confirm a moderate but statistically significant nonlinear RUF concentration-dose relationship. At steady state, the trough concentrations of RUF increase in a less than dose proportional manner. Children (younger than 12 years) had significantly lower RUF concentrations (19.0%, P < 0.001) than adults (18 years or older) on comparable RUF doses per body weight. VPA was the most frequent comedication (51%) in our patient group. Mean RUF concentrations were 86.6% higher when VPA concentrations were greater than 90 μg/mL (P < 0.001) and 45.4% higher when VPA concentrations were between 50 and 90 μg/mL (P < 0.001) but not significantly different at VPA concentrations less than 50 μg/mL (4.4%, P > 0.1) compared with combinations without VPA. In combination with EIAEDs, mean RUF concentrations were 21.8% lower (P = 0.002) compared with combinations without EIAEDs. However, the group of AEDs classified as EIAEDs was heterogeneous and the number of patients, especially of children with EIAEDs, was relatively small. Our data indicate that oxcarbazepine and, especially, methsuximide decrease RUF concentrations as well. Therapeutic drug monitoring might be helpful because RUF concentrations differ markedly in patients on comparable RUF doses.

Pharmacologic treatment of intractable epilepsy in children: a syndrome-based approach

The successful pharmacologic treatment of intractable childhood epilepsy is predicated upon an accurate classification of the epilepsy syndrome. The selection of an antiepileptic drug is facilitated by the knowledge of syndrome-specific efficacy, the anticipation of potential side effects, and a careful risk-benefit assessment tailored to each patient. As such, the identification of comorbidities and careful monitoring for treatment-emergent adverse events, especially cognitive and behavioral effects, is of utmost importance. Especially in refractory cases, polypharmacy may increase the likelihood of side effects, but carefully chosen combinations can result in synergistic benefit. For most epilepsy syndromes, newer antiepileptic drugs typically yield equivalent efficacy and superior tolerability. Nevertheless, continued research is needed to further contrast the syndrome-specific efficacy and tolerability of available drugs and to foster the development of new agents with superior efficacy and side effect profiles.

Low long-term efficacy and tolerability of add-on rufinamide in patients with Dravet syndrome

In this retrospective European multicenter study we evaluated the efficacy and tolerability of rufinamide in patients with Dravet syndrome and refractory seizures. Twenty patients were included; in 16 patients a SCN1A mutation was detected. The responder rate after 6 months was 20%, and after 34 months, 5%. The retention rate was 45% after 6 months and 5% after 34 months. Rufinamide treatment was stopped because of aggravation of seizures (30%), no effect (45%), and side effects (10%). The efficacy and long-term retention rate were low in our patients with Dravet syndrome and refractory seizures, far lower than in patients with Lennox-Gastaut syndrome; one-third of our patients experienced seizure aggravation. Therefore, rufinamide does not seem to be a suitable option for long-term treatment in patients with Dravet syndrome.

Rufinamide for pediatric patients with Lennox-Gastaut syndrome: a comprehensive overview

Rufinamide is a triazole derivative with broad-spectrum antiepileptic effects that is unrelated to any antiepileptic drug currently on the market. The European Commission and the US FDA approved rufinamide in 2007 and 2008, respectively, for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome in children 4 years of age or older and adults. The mechanism of action of rufinamide is not completely understood but it is believed to prolong the inactive state of sodium channels, therefore limiting excessive firing of sodium-dependent action potentials. Rufinamide is well absorbed when taken with food, with an absolute bioavailability between 70% and 85%. The elimination half-life of the drug is around 6-10 hours, with a time to maximum plasma concentration (C(max)) of approximately 4-6 hours. The C(max) at a dosage of 10 mg/kg/day and 30 mg/kg/day is 4.01 μg/mL and 8.68 μg/mL, respectively, and the area under the plasma concentration-time curve from time 0 to 12 hours was 37.8 ± 47 μg · h/mL and 89.3 ± 58 μg · h/mL, respectively. Rufinamide exerts non-linear pharmacokinetics with increasing doses. The volume of distribution in children is similar to that in adults (0.8-1.2 L/kg) and the drug binds rather poorly to plasma protein (26.2-34.8%). Rufinamide is mainly metabolized by carboxylesterases to an inactive metabolite (CGP 47292), and the majority of the metabolites are excreted in the urine (91%). No dosage adjustment is required in patients with renal dysfunction. Rufinamide does not affect the plasma concentration of other antiepileptics, but phenytoin, phenobarbital, valproate, and primidone affect the clearance of rufinamide. In a clinical study of 138 patients averaging 12 years of age, rufinamide used as an adjunctive therapy (with an initial dosage of 10 mg/kg/day up to a target dosage of 45 mg/kg/day) in patients with Lennox-Gastaut syndrome reduced the median total seizure frequency by 32.7% versus 11.7% in the placebo group (p = 0.0015). Similar reduction in total seizure frequency was maintained in the extension phase of this study. In other studies, rufinamide also seemed to provide improvement in both partial seizures and refractory epilepsy, but further studies need to validate this observation and to identify its clinical significance. Rufinamide is usually started orally at 10 mg/kg/day, titrating up by 10 mg/kg/day every 2 days to a target dosage of 45 mg/kg/day divided twice daily (maximum dosage of 3200 mg/day). Dosing of rufinamide has not been established in patients <4 years of age. Rufinamide is available as 100, 200, and 400 mg tablets in Europe, and 200 and 400 mg tablets in the US; a suspension of 40 mg/mL can be prepared extemporaneously. Rufinamide is well tolerated, with the most common adverse effects being dizziness, fatigue, nausea, vomiting, diplopia, and somnolence. From the current data, rufinamide serves as an adjunctive therapy in the management of Lennox-Gastaut syndrome. Further studies need to evaluate its efficacy as a first-line agent in the management of this neurologic disorder.

Rufinamide for the treatment of epileptic spasms

OBJECTIVE

The purpose of this study was to determine the safety and efficacy of rufinamide for treatment of epileptic spasms.

METHODS

We retrospectively reviewed patients treated with rufinamide for epileptic spasms from January 2009 to March 2010. Age, presence of hypsarrhythmia, change in seizure frequency following rufinamide initiation, and side effects were assessed. Patients who had a ≥ 50% reduction in spasm frequency were considered responders.

RESULTS

Of all 107 children treated with rufinamide during the study period, 38 (36%) had epileptic spasms. Median patient age was 7 years (range: 17 months to 23). One patient had hypsarrhythmia at the time of treatment with rufinamide, and 9 other patients had a history of hypsarrhythmia. Median starting dose of rufinamide was 9 mg/kg/day (range: 2-18) and median final treatment dose was 39 mg/kg/day (range: 8-92). All patients were receiving concurrent antiepileptic drug therapy, with the median number of antiepileptic drugs being 3 (range: 2-6). Median duration of follow-up since starting rufinamide was 171 days (range: 10-408). Responder rate was 53%. Median reduction in spasm frequency was 50% (interquartile range=-56 to 85%, P<0.05). Two patients (5%) achieved a >99% reduction in spasms. Rufinamide was discontinued in 7 of 38 patients (18%) because of lack of efficacy, worsening seizures, or other side effects. Minor side effects were reported in 14 of 38 patients (37%).

CONCLUSIONS

Rufinamide appears to be a well-tolerated and efficacious adjunctive therapeutic option for children with epileptic spasms. A prospective study is warranted to validate our observations.

Pharmacotherapy for children and adolescents with epilepsy

INTRODUCTION

Childhood epilepsies are the most frequent neurological problems that occur in children. Despite the introduction of new antiepileptic drugs (AEDs) 25-30% of children with epilepsy remain refractory to medical therapy.

AREAS COVERED

This review aims to highlight the main published data on the treatment of childhood epilepsy. The electronic database, PubMed, and abstract proceedings were used to identify studies. The aim of antiepileptic therapy should be to provide complete seizure control, if possible without the burden of any side effect. Since 1993, new agents have been approved for use as an antiepileptic. Although there are few published data (especially in pediatric populations) to establish that the second-generation AEDs are more efficacious than the older AEDs, they appear to have better tolerability.

EXPERT OPINION

Old AEDs are efficacious agents that continue to play a major role in the current treatment of epilepsy. These agents actually remain the first-line treatment for many specific seizure types or epileptic syndromes. The new AEDs were initially approved as adjunct agents and--subsequently--as monotherapy for various seizure types in the adult and children. Despite these improvements, few AEDs are now considered to be a first-choice for the treatment of epilepsy in children.

New drugs for pediatric epilepsy

The last 2 decades have witnessed an unprecedented period of new antiepileptic drug (AED) development. Newer-generation AEDs have been developed with the intention of improving the ease of use, decreasing drug interactions, decreasing adverse side effects, and identifying drugs with unique mechanisms of action, some of which may bear relevance to potential neuroprotective activity. Drug trials have also been refined in some cases to evaluate AED efficacy in children and against distinct epilepsy syndromes. This progress provides many new treatment options for the child neurologist facing children with epilepsy but also introduces the burden of determining appropriate AED choices. Here we highlight 6 new antiepileptic medications recently approved or pending approval for use in the United States: lacosamide, rufinamide, vigabatrin, retigabine, brivaracetam, and clobazam. For each of these medications, we present information regarding the history of drug development, proposed mechanism(s) of action, pharmacokinetics and recommended dosing, evidence for clinical efficacy, tolerability, and when, available, any unique features that are relevant for the pediatric population.

Experience with rufinamide in a pediatric population: a single center's experience

Rufinamide is a new antiepileptic drug recently approved as adjunctive treatment for generalized seizures in Lennox-Gastaut syndrome. We undertook a retrospective analysis of 77 patients with refractory epilepsy and receiving rufinamide to evaluate the drug's efficacy, tolerability, safety, and dosing schedules. It appeared efficacious in diverse epilepsy syndromes, with the highest responder rate in focal cryptogenic epilepsies (81.1% of patients with >50% response rate), and in diverse seizure types, with the highest responder rate in tonic/atonic and partial seizures (48.6% and 46.7% of patients with >50% response rate, respectively). Rufinamide was well tolerated: only 13% of patients developed side effects necessitating drug withdrawal. These findings suggest that rufinamide may possess good efficacy and tolerability, and that its efficacy may extend to epilepsy syndromes beyond Lennox-Gastaut, including both partial and generalized epilepsy syndromes.

Therapeutic Drug Monitoring of the Newer Anti-Epilepsy Medications

In the past twenty years, 14 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. In general, the clinical utility of therapeutic drug monitoring has not been established in clinical trials for these new anticonvulsants, and clear guidelines for drug monitoring have yet to be defined. The antiepileptic drugs with the strongest justifications for drug monitoring are lamotrigine, oxcarbazepine, stiripentol, and zonisamide. Stiripentol and tiagabine are strongly protein bound and are candidates for free drug monitoring. Therapeutic drug monitoring has lower utility for gabapentin, pregabalin, and vigabatrin. Measurement of salivary drug concentrations has potential utility for therapeutic drug monitoring of lamotrigine, levetiracetam, and topiramate. Therapeutic drug monitoring of the new antiepileptic drugs will be discussed in managing patients with epilepsy.

Therapeutic Drug Monitoring of the Newer Anti-Epilepsy Medications

In the past twenty years, 14 new antiepileptic drugs have been approved for use in the United States and/or Europe. These drugs are eslicarbazepine acetate, felbamate, gabapentin, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, pregabalin, rufinamide, stiripentol, tiagabine, topiramate, vigabatrin and zonisamide. In general, the clinical utility of therapeutic drug monitoring has not been established in clinical trials for these new anticonvulsants, and clear guidelines for drug monitoring have yet to be defined. The antiepileptic drugs with the strongest justifications for drug monitoring are lamotrigine, oxcarbazepine, stiripentol, and zonisamide. Stiripentol and tiagabine are strongly protein bound and are candidates for free drug monitoring. Therapeutic drug monitoring has lower utility for gabapentin, pregabalin, and vigabatrin. Measurement of salivary drug concentrations has potential utility for therapeutic drug monitoring of lamotrigine, levetiracetam, and topiramate. Therapeutic drug monitoring of the new antiepileptic drugs will be discussed in managing patients with epilepsy.