Rufinamide: Clinical pharmacokinetics and concentrationresponse relationships in patients with epilepsy

Host factors affecting antiepileptic drug delivery-pharmacokinetic variability

Antiepileptic drugs (AEDs) are the mainstay in the treatment of epilepsy, one of the most common serious chronic neurological disorders. AEDs display extensive pharmacological variability between and within patients, and a major determinant of differences in response to treatment is pharmacokinetic variability. Host factors affecting AED delivery may be defined as the pharmacokinetic characteristics that determine the AED delivery to the site of action, the epileptic focus. Individual differences may occur in absorption, distribution, metabolism and excretion. These differences can be determined by genetic factors including gender and ethnicity, but the pharmacokinetics of AEDs can also be affected by age, specific physiological states in life, such as pregnancy, or pathological conditions including hepatic and renal insufficiency. Pharmacokinetic interactions with other drugs are another important source of variability in response to AEDs. Pharmacokinetic characteristics of the presently available AEDs are discussed in this review as well as their clinical implications.

Current oral and non-oral routes of antiepileptic drug delivery

Antiepileptic drugs are commonly given orally for chronic treatment of epilepsy. The treatment of epilepsy requires administration of medications for both acute and chronic treatment using multiple types of formulations. Parenteral routes are used when the oral route is unavailable or a rapid clinical response is required. Lorazepam and midazolam can be administered by the buccal, sublingual or intranasal routes. Consensus documents recommend rectal diazepam, buccal midazolam or intranasal midazolam for the out-of-hospital treatment of early status epilepticus. In the United States, diazepam is the only FDA approved rectal formulation. With the lack of parenteral, buccal or intranasal formulations for many of the antiepileptic drugs, the use of the rectal route of delivery to treat acute seizures or to maintain therapeutic concentrations is suitable for many, but not all antiepileptic medications. There is a significant need for new non-oral formulations of the antiepileptic drugs when oral administration is not possible.

Rufinamide efficacy and safety as adjunctive treatment in children with focal drug resistant epilepsy: the first Italian prospective study

Rufinamide is a new antiepileptic drug approved as add-on treatment in Lennox-Gastaut syndrome from the age of 4 years, and for the treatment of focal seizures in adults and adolescents. The aim of this prospective study was to evaluate the safety and efficacy of add-on Rufinamide in the treatment of childhood focal drug resistant epilepsy. We recruited 70 patients for a prospective, add-on, open-label study. Inclusion criteria were: 3 years of age or more; focal drug resistant epilepsy despite the use of three previous AEDs; use of at least one other AED, but no more than three at baseline; more than one seizure per month in the previous 6 months. Rufinamide efficacy was observed up to 12 months of follow-up, with a total responder rate of 38.57%. We found the best results in focal epilepsies due to structural/metabolic etiology (42.6%). The responder rate was similar for focal seizures with secondary generalization, simple focal seizures other than myoclonic jerks, and complex partial seizures. Response to Rufinamide was not related to the age. Our experience suggests that Rufinamide can be effective in reducing focal seizure frequency in children with drug resistant epilepsy, and that it can be considered as a safe drug.

Age-related inducibility of carboxylesterases by the antiepileptic agent phenobarbital and implications in drug metabolism and lipid accumulation

Carboxylesterases (CES) constitute a class of hydrolytic enzymes that play critical roles in drug metabolism and lipid mobilization. Previous studies with a large number of human liver samples have suggested that the inducibility of carboxylesterases is inversely related with age. To directly test this possibility, neonatal (10 days of age) and adult mice were treated with the antiepileptic agent phenobarbital. The expression and hydrolytic activity were determined on six major carboxylesterases including ces1d, the ortholog of human CES1. Without exception, all carboxylesterases tested were induced to a greater extent in neonatal than adult mice. The induction was detected at mRNA, protein and catalytic levels. Ces1d was greatly induced and found to rapidly hydrolyze the antiplatelet agent clopidogrel and support the accumulation of neutral lipids. Phenobarbital represents a large number of therapeutic agents that induce drug metabolizing enzymes and transporters in a species-conserved manner. The higher inducibility of carboxylesterases in the developmental age likely represents a general phenomenon cross species including human. Consequently, individuals in the developmental age may experience greater drug-drug interactions. The greater induction of ces1d also provides a molecular explanation to the clinical observation that children on antiepileptic drugs increase plasma lipids.

The use of newer antiepileptic drugs in patients with renal failure

Seizures and chronic kidney disease are both common and often coexist. Treating seizures in patients with renal failure, including those on dialysis, is a challenge that is frequently encountered, especially in the inpatient setting. For the newer antiepileptic drugs, there are limited data available, so an understanding of how each drug is affected by kidney disease and dialysis is critical in order to make rational choices qualitatively (which drug) and quantitatively (dosing). Generally, newer (second-generation) antiepileptic drugs are associated with fewer systemic side effects and drug-drug interactions, so they tend to be preferred in this population. The landscape of antiepileptic drugs is constantly evolving, with new compounds being released on a regular basis. Thus, several new agents have become available since the last review of this topic (in 2006) and these are the ones discussed here. Most require dosage adjustment according to the degree of renal failure, and most require extra doses after dialysis.

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.

New and emerging treatments for epilepsy: review of clinical studies of lacosamide, eslicarbazepine acetate, ezogabine, rufinamide, perampanel, and electrical stimulation therapy

Although many different medical and surgical treatment options for epilepsy exist, approximately 30% of epilepsy patients remain poorly controlled. For those patients who are refractory to medical treatment, epilepsy surgery often provides meaningful improvement. However, when surgical resection of epileptic foci cannot be offered or failed, combined administration of AEDs or the application of novel AEDs is the most appropriate therapeutic options. The most recent AEDs tend to offer new mechanisms of action and more favorable safety profiles than the first generation of AEDs. More recently, alternative options of thalamic or cortical stimulation emerged as potentiall effective treatment for epilepsy. The purpose of this article is to compare and review clinical information for the new and emerging medications such as lacosamide, eslicarbazepine acetate, ezogabine (retigabine), rufinamide, perampanel, as well as deep brain stimulation and responsive neurostimulation devices.

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.

Antiepileptic drug interactions - principles and clinical implications

Antiepileptic drugs (AEDs) are widely used as long-term adjunctive therapy or as monotherapy in epilepsy and other indications and consist of a group of drugs that are highly susceptible to drug interactions. The purpose of the present review is to focus upon clinically relevant interactions where AEDs are involved and especially on pharmacokinetic interactions. The older AEDs are susceptible to cause induction (carbamazepine, phenobarbital, phenytoin, primidone) or inhibition (valproic acid), resulting in a decrease or increase, respectively, in the serum concentration of other AEDs, as well as other drug classes (anticoagulants, oral contraceptives, antidepressants, antipsychotics, antimicrobal drugs, antineoplastic drugs, and immunosupressants). Conversely, the serum concentrations of AEDs may be increased by enzyme inhibitors among antidepressants and antipsychotics, antimicrobal drugs (as macrolides or isoniazid) and decreased by other mechanisms as induction, reduced absorption or excretion (as oral contraceptives, cimetidine, probenicid and antacides). Pharmacokinetic interactions involving newer AEDs include the enzyme inhibitors felbamate, rufinamide, and stiripentol and the inducers oxcarbazepine and topiramate. Lamotrigine is affected by these drugs, older AEDs and other drug classes as oral contraceptives. Individual AED interactions may be divided into three levels depending on the clinical consequences of alterations in serum concentrations. This approach may point to interactions of specific importance, although it should be implemented with caution, as it is not meant to oversimplify fact matters. Level 1 involves serious clinical consequences, and the combination should be avoided. Level 2 usually implies cautiousness and possible dosage adjustments, as the combination may not be possible to avoid. Level 3 refers to interactions where dosage adjustments are usually not necessary. Updated knowledge regarding drug interactions is important to predict the potential for harmful or lacking effects involving AEDs.

Seizure management in the setting of hepatic disease

OPINION STATEMENT

In the past 20 years, many antiepileptic drugs (AEDs) have been marketed that are not significantly metabolized by the liver, but some patients still require the use of older and more metabolically complex AEDs for optimal seizure control, and current economic and insurance-coverage limitations have forced many patients to switch to less expensive agents, which are often the older AEDs. For the patient with hepatic disease, it is clearly preferable to use medications with little potential to exacerbate their condition. In my practice, I try to use agents with simpler metabolism, especially for patients with multiple medical problems. Doing this can mean using AEDs in monotherapy that are FDA-approved only for adjunctive use. I also find that older agents and hepatically metabolized AEDs can be the most appropriate for particular patients. Selection of the optimal seizure medication requires consideration of multiple factors, only one of which is the impact on liver function. I routinely obtain an executive laboratory panel at least yearly for even the healthiest of patients, to reassure both the patient and myself that the metabolism of their AED regimen is not significantly affected. Occasionally, a change or abnormality in liver function is identified. Certainly hepatic disease can make epilepsy management more difficult, and communication between the neurologist and the other treating physicians is a necessity, although the neurologist and the hepatologist may have differing opinions on how to respond to worsening liver function. Concern about potential liver damage by AEDs may prompt unnecessary discontinuation, sometimes with disastrous consequences for seizure control. Overly complex AED regimens can cause underlying liver problems to worsen. Clinical observation and judgment must complement the data derived from laboratory parameters. Worsening hepatic disease can also result in encephalopathic states that worsen or mimic seizures. The EEG can often be helpful in differentiating these conditions and is crucial in determining appropriate epilepsy therapy.

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.

Activation of suicidal ideation with adjunctive rufinamide in bipolar disorder

Antiepileptic drugs are effective psychotropics, especially for bipolar disorder, which leads to their use off-label in treatment-refractory cases. A recent publication suggests that rufinamide may be beneficial adjunctively for bipolar disorder with comorbid psychopathology. This report addresses two negative cases with significant psychiatric adverse effects: increased depression, agitation, and activation of suicidal ideation. These findings suggest that adjunctive rufinamide may lead to increased suicidal ideation in patients with treatment-refractory bipolar disorder. Secondary to the course of severe bipolar disorder, rufinamide cannot be specifically implicated; however, clinicians should be aware of this potential significant adverse effect and monitor high-risk patients. Further studies are required to address rufinamide treatment efficacy and severity of adverse effects in patients with bipolar disorder.

Pharmacotherapy of epilepsy: newly approved and developmental agents

This article discusses seven newly available antiepileptic drugs (AEDs) and agents in phase III development. Lacosamide, licensed as an adjunctive treatment for partial-onset seizures, primarily acts by enhancing sodium channel slow inactivation. At daily doses of 200-600 mg, the drug significantly reduced partial-onset seizures in adults with refractory epilepsy. The most common adverse effects are CNS related. Rufinamide, available as adjunctive treatment for seizures associated with Lennox-Gastaut syndrome, has an unclear mechanism of action, although it does block voltage-dependent sodium channels. Coadministration of valproic acid significantly increases rufinamide circulating concentrations. The drug has been shown to have efficacy for partial-onset, primary generalized tonic-clonic, tonic-atonic, absence and atypical absence seizures. Adverse effects are mainly somnolence, nausea and vomiting. Eslicarbazepine acetate, a carbamazepine analogue, was recently licensed as adjunctive treatment for partial-onset seizures. Eslicarbazepine acetate acts at voltage-gated sodium channels, although the precise mechanism of action is unclear. The drug had efficacy for partial-onset seizures in three randomized, double-blind, placebo-controlled studies, using 400, 800 or 1200 mg/day. Adverse effects include dizziness and somnolence. Retigabine (ezogabine) exerts its anticonvulsant effect through the opening of neuronal voltage-gated potassium channels. Following significant seizure reduction rates at dosages of 600, 900 and 1200 mg/day, license applications have been submitted for its use as adjunctive treatment for patients with partial-onset seizures. Dose-related adverse effects include somnolence, confusion and dizziness. Brivaracetam is the n-propyl analogue of levetiracetam. Mixed results have been obtained in phase III studies in patients with partial-onset seizures, and further trials in children, patients with photosensitive epilepsy and patients with partial-onset seizures are ongoing. Dizziness, headache and somnolence are the most common adverse effects reported. Perampanel was designed as an AMPA-type glutamate receptor antagonist. Following encouraging results from phase II studies in patients with refractory partial-onset seizures, recruitment for phase III trials is almost complete. Ganaxolone is a neurosteroid with potent antiepileptic activity that modulates GABA(A) receptors in the CNS. Ganaxolone has shown promise in a variety of seizure types. Dizziness and somnolence have been reported in some patients. The availability of new AEDs has widened the choices for clinicians treating patients with epilepsy. However, given the minimal improvement in prognosis and disappointing efficacy outcomes in double-blind, placebo-controlled, dose-ranging regulatory trials, it seems unlikely that these novel agents will have a major impact on outcomes for people with epilepsy.

Update on rufinamide in childhood epilepsy

Rufinamide is an orally active, structurally novel compound (1-[(2,6-difluorophenil1) methyl1]-1 hydro 1,2,3-triazole-4 carboxamide), which is structurally distinct from other anticonvulsant drugs. It was granted orphan drug status for the adjunctive treatment of Lennox-Gastaut syndrome (LGS) in the United States in 2004, and released for use in Europe in 2007. In January 2009, rufinamide was approved by the United States Food and Drug Administration for treatment of LGS in children 4 years of age and older. It is also approved for adjunctive treatment for partial seizures in adults and adolescents. Rufinamide's efficacy mainly against atonic/tonic seizures in patients with LGS seems nowadays indubitable and has been confirmed both in randomized controlled trial and in open label extension studies. More recently, rufinamide was evaluated for the adjunctive treatment of childhood-onset epileptic encephalopathies and epileptic syndromes other than LGS, including epileptic spasms, multifocal epileptic encephalopathy with spasm/tonic seizures, myoclonic-astatic epilepsy, Dravet syndrome and malignant migrating partial seizures in infancy. This review updates the existing literature data on the efficacy and safety/tolerability of rufinamide in childhood-onset epilepsy syndromes.

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.

Treating Lennox-Gastaut syndrome in epileptic pediatric patients with third-generation rufinamide

Lennox-Gastaut syndrome (LGS) is a rare but debilitating pediatric epileptic encephalopathy characterized by multiple intractable seizure types. Treatment of LGS is challenging because of the small number of antiepileptic drugs (AEDs) which are effective for this syndrome, as well as the need for polytherapy in the majority of patients. This review focuses on the treatment of LGS with rufinamide, a recently approved third-generation AED with reported efficacy as adjunctive therapy for LGS. All relevant papers identified through a PubMed search on the treatment of LGS with rufinamide were reviewed. To date, the literature suggests improvements in seizure frequency for pediatric patients with LGS on rufinamide. Rufinamide appears to be especially effective for atonic or drop attack seizures. Rufinamide also displays a favorable adverse event profile compared with the older anticonvulsants, as well as a minimal number of drug interactions, making it a promising option for the adjunctive treatment of seizures associated with LGS.

A randomized, double-blind, placebo-controlled, parallel-group study of rufinamide as adjunctive therapy for refractory partial-onset seizures

PURPOSE

Efficacy and safety of adjunctive rufinamide (3,200 mg/day) was assessed in adolescents and adults with inadequately controlled partial-onset seizures receiving maintenance therapy with up to three antiepileptic drugs (AEDs).

METHODS

This randomized, double-blind, placebo-controlled, parallel-group, multicenter study comprised a 56-day baseline phase (BP), 12-day titration phase, and 84-day maintenance phase (MP). The primary efficacy variable was percentage change in total partial seizure frequency per 28 days (MP vs. BP). Secondary efficacy outcome measures included ≥50% responder rate and reduction in mean total partial seizure frequency during the MP. Safety and tolerability evaluation included adverse events (AEs), physical and neurologic examinations, and laboratory values. Pharmacokinetic and pharmacodynamic assessments were conducted.

RESULTS

Three hundred fifty-seven patients were randomized: 176 to rufinamide and 181 to placebo. Patients had a median of 13.3 seizures per 28 days during BP; 86% were receiving ≥2 AEDs. For the intent-to-treat population, the median percentage reduction in total partial seizure frequency per 28 days was 23.25 for rufinamide versus 9.80 for placebo (p = 0.007). Rufinamide-treated patients were more than twice as likely to have had a ≥50% reduction in partial seizure frequency (32.5% vs. 14.3%; p < 0.001) and had a greater reduction in median total partial seizure rate per 28 days during the MP (13.2 vs. 5.2; p < 0.001). Treatment-emergent AEs occurring at ≥5% higher incidence in the rufinamide group compared with placebo were dizziness, fatigue, nausea, somnolence, and diplopia.

CONCLUSIONS

Adjunctive treatment with rufinamide reduced total partial seizures in refractory patients. AEs reported were consistent with the known tolerability profile of rufinamide.

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.

Rufinamide: a novel broad-spectrum antiepileptic drug

The last 20 years have witnessed a tremendous explosion in the number of antiepileptic drugs (AEDs) as well as the introduction of AEDS developed for specific epilepsy syndromes. The study of the efficacy and side effect profile of AEDs for unique epilepsy syndromes has allowed neurologists to utilize evidence-based medicine when treating patients. In late 2008, the Food and Drug Administration approved rufinamide for adjunctive use in the treatment of seizures associated with Lennox-Gastaut syndrome. This unique chemical compound is also the first new AED to reach the market in the United States having a pediatric indication prior to approval for adults. Rufinamide appears to have a broad spectrum of efficacy, is well tolerated, and may be rapidly initiated--properties that will likely extend its use outside of Lennox-Gastaut syndrome.

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.

Supporting the recommended paediatric dosing regimen for rufinamide in Lennox-Gastaut syndrome using clinical trial simulation

Rufinamide was approved for the treatment of seizures associated with Lennox-Gastaut syndrome (LGS) as adjunctive therapy in patients aged 4 years and older. Rufinamide pharmacokinetics (PK) has been established on pooled data from several clinical studies in epilepsy, including one in LGS patients. Demographic covariates and drug-drug interactions with several antiepileptic drugs have been explored using population PK modelling. Two types of drug-drug interactions models were developed and compared. The PK analysis demonstrated that the coadministration of valproate decreases rufinamide clearance, requiring potential dose adjustment. To explore rufinamide exposure under different dosing regimens in LGS patients, clinical trial simulations were performed. The objective of the simulations was to select the doses giving an exposure shown to be safe and efficacious in larger populations. The concentrations simulated in a subgroup of patients with body weight less than 30 kg presented a larger inter-individual variability than in other patients. Additional simulations demonstrated that this increased variability was due partly to greater valproate concentrations in some of the children treated with rufinamide. Simulations of the rufinamide exposure under different maximum daily dose in presence and in absence of valproate co-administration were used to establish the dosing recommendation. The simulations support the proposal of a lower maximum daily rufinamide dose for patients under 30 kg receiving both drugs: the dose of 600 mg/day was proposed as a maximum daily dose in children also receiving valproate concomitantly, whereas in absence of valproate, the maximum daily dose is 1000 mg/day.

Key factors in the discovery and development of new antiepileptic drugs

Since the early 1990s, many new antiepileptic drugs (AEDs) that offer appreciable advantages in terms of their favourable pharmacokinetics, improved tolerability and lower potential for drug-drug interactions have entered the market. However, despite the therapeutic arsenal of old and new AEDs, approximately 30% of patients with epilepsy still suffer from seizures. Thus, there remains a substantial need for the development of more efficacious AEDs for patients with refractory seizures. Here, we briefly review the emerging knowledge on the pathological basis of epilepsy and how it might best be used in the design of new therapeutics. We also discuss the current approach to AED discovery and highlight some of the unique features of newer models of pharmacoresistance and epileptogenesis that have emerged in recent years.

A 24-week multicenter, randomized, double-blind, parallel-group, dose-ranging study of rufinamide in adults and adolescents with inadequately controlled partial seizures

OBJECTIVE

To assess the efficacy, safety, tolerability, and pharmacokinetics of adjunctive rufinamide in adults and adolescents with inadequately controlled partial seizures receiving treatment with one to three concomitant antiepileptic drugs (AEDs).

METHODS

A 24-week multicenter Phase II clinical study was conducted (n=647), comprising a 12-week prospective baseline phase and a 12-week randomized double-blind, parallel-group, five-arm (placebo and rufinamide 200, 400, 800, and 1600mg/day) treatment phase.

RESULTS

The linear trend of dose response for seizure frequency per 28 days in the double-blind treatment phase - the primary efficacy outcome measure - was statistically significant in favor of rufinamide (estimated slope=-0.049, P=0.003; minimally efficacious dose, 400mg/day). Response rates, defined as a >or=50% reduction in seizure frequency per 28 days, also revealed a significant linear trend of dose response (P=0.0019, logistic regression analysis). Adverse events were comparable between placebo and all rufinamide groups except the 1600mg/day group; no safety signals were observed.

CONCLUSIONS

These results suggest that in the dose range of 400-1600mg/day, add-on rufinamide therapy may benefit patients with inadequately controlled partial seizures and is generally well tolerated. These data also suggest that higher doses may confer additional efficacy without adversely affecting safety and tolerability.

Safety and tolerability of rufinamide in children with epilepsy: a pooled analysis of 7 clinical studies

Rufinamide is a novel antiepileptic agent recently approved in the United States for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome. To help inform clinical decision making, the authors analyzed safety and tolerability data from the entire pediatric population in the rufinamide epilepsy clinical development program. The analysis population comprised 212 rufinamide-treated (age range 3-16 years) and 197 placebo patients (age range 4-17 years) in the double-blind studies, and 391 patients receiving rufinamide in the double-blind and/or open-label extensions. The most common adverse effects observed in rufinamide-treated patients in the double-blind studies were somnolence, vomiting, and headache. Changes in laboratory values, vital signs, and weight were generally clinically insignificant. This pooled analysis of data from pediatric patients in clinical studies of rufinamide for the treatment of seizures, mainly as adjunctive therapy, suggests a favorable safety and tolerability profile in this patient population.

Onset of action and seizure control in Lennox-Gaustaut syndrome: focus on rufinamide

Lennox-Gaustaut syndrome is an electroclinical epilepsy syndrome characterized by the triad of electroencephalogram showing diffuse slow spike-and-wave discharges and paroxysmal fast activity, multiple intractable seizure types, and cognitive impairment. The intractability to seizure medications and cognitive impairment gives rise to eventual institutionalized patient care. Only a small subset of seizure medications has been shown to be helpful in seizure control. Most patients take up to 3 medications at high therapeutic dosing and are susceptible to medication-induced side effects. The lack of medication efficacy in seizure control has led one meta-analysis to conclude that there is no single medication that is highly efficacious in controlling seizures in this syndrome. On this background, a new and structurally novel seizure medication, rufinamide, has been found to be beneficial in the treatment of seizures in this syndrome. In a multicenter, double-blinded, randomized, placebo-controlled study, rufinamide was found to reduce seizures by over 30%. More importantly, it reduced the frequency of the seizure type that induces most of the morbidity of this syndrome, the drop seizure, by over 40%. There were few side effects, the medication was well tolerated, and in the open labeled extension study, tolerance was not found. In this review, we describe the main electroclinical features of Lennox-Gaustaut syndrome and summarize the few controlled studies that have contributed to its rational treatment. Currently, there is no single agent or combination of agents that effectively treat the multiple seizure types and co-morbidities in this syndrome. Our focus will be on the role of the new medication rufinamide in seizure reduction in patients with Lennox-Gaustaut syndrome.

Rufinamide

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing inservices. A comprehensive target drug utilization evaluation (DUE) is also provided each month. With a subscription, the monographs are sent in print and are also available online. Monographs can be customized to meet the needs of a facility. Subscribers to The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X.). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The May 2009 monograph topics are febuxostat, antithrombin (recombinant), calcitriol ointment, trabectedin, and tesamorelin. The class review is on drugs used in the therapy of benign prostatic hyperplasia, and the DUE is on febuxostat.

Pharmacological management of epilepsy: recent advances and future prospects

There is still a need for new antiepileptic drugs (AEDs) as the clinical efficacy, tolerability, toxicity or pharmacokinetic properties of existing AEDs may not be satisfactory. One new AED has recently been approved (rufinamide in 2007) and six others are in late-stage development (phase III and onwards) [brivaracetam, carisbamate, eslicarbazepine, lacosamide, retigabine and stiripentol]. The purpose of this review is to provide updated data on proposed mechanisms of action, efficacy and tolerability on these new AEDs, and to discuss the rationale for their development and possible advantages compared with existing treatment, based on recent publications and MEDLINE searches.Rufinamide, brivaracetam and stiripentol have been given the status of orphan drugs. Rufinamide was approved in Europe in 2007 for the use in Lennox-Gastaut syndrome. Brivaracetam has gained orphan status for development in progressive and symptomatic myoclonic seizures in Europe and the US, respectively. Stiripentol has gained orphan status in children with Dravet's syndrome and pharmaco-resistant epilepsy. All of these drugs demonstrate efficacy as adjunctive therapy in partial seizures. Three of the drugs are derivatives of existing AEDs: brivaracetam is a derivative of levetiracetam with improved affinity for the target molecule; carisbamate is a derivative of felbamate with improved tolerability; and eslicarbazepine is a derivative of carbamazepine with less interaction potential and no auto-induction. Lacosamide, retigabine, rufinamide and stiripentol are new compounds, unrelated to other AEDs.Further investigation and development of new broad-spectrum drugs is important for improved treatment of patients with epilepsy and other neurological and psychiatric disorders.

Update on the management of Lennox-Gastaut syndrome with a focus on rufinamide

OBJECTIVE

This review summarizes the treatment of Lennox-Gastaut syndrome, an intractable epileptic encephalopathy of early childhood. In particular, the review focuses on rufinamide, a recently released anticonvulsant medication with reported effectiveness in this epilepsy syndrome.

METHODS

A systematic literature search (PubMed) was performed to review the existing literature pertaining to the treatment of Lennox-Gastaut syndrome as well as studies involving rufinamide as an anticonvulsant medication.

RESULTS

The published literature to date documents a beneficial effect of rufinamide on children over 4 years old with Lennox-Gastaut syndrome. Studies indicate a significant decrease in tonic and atonic seizure frequency as well as total seizure frequency compared to placebo-treated children. Rufinamide appears to be well tolerated and a safe medication, somnolence and vomiting being the most common side effects.

CONCLUSIONS

Rufinamide is a promising adjunctive therapy for Lennox-Gastaut syndrome, an intractable childhood epilepsy. To ensure its optimal effectiveness, clinicians must be familiar with the medication's clinical response profile and potential for adverse effects.

Treatment of Lennox-Gastaut syndrome: overview and recent findings

Lennox-Gastaut syndrome (LGS) is a rare, age-related syndrome, characterized by multiple seizure types, a specific electro-encephalographic pattern, and mental regression. However, published data on the etiology, evolution, and therapeutic approach of LGS are contradictory, partly because the precise definition of LGS used in the literature varies. In the most recent classification, LGS belongs to the epileptic encephalopathies and is highly refractory to all antiepileptic drugs. Numerous treatments, medical and non-medical, have been proposed and results mostly from open studies or case series have been published. Sometimes, patients with LGS are included in a more global group of patients with refractory epilepsy. Only 6 randomized double-blind controlled trials of medical treatments, which included patients with LGS, have been published. Overall, treatment is rarely effective and the final prognosis remains poor in spite of new therapeutic strategies. Co-morbidities need specific treatment. This paper summarizes the definition, diagnosis and therapeutic approach to LGS, including not only recognized antiepileptic drugs, but also "off label" medications, immune therapy, diet, surgery and some perspectives for the future.

Antiepileptic drugs--best practice guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies

Although no randomized studies have demonstrated a positive impact of therapeutic drug monitoring (TDM) on clinical outcome in epilepsy, evidence from nonrandomized studies and everyday clinical experience does indicate that measuring serum concentrations of old and new generation antiepileptic drugs (AEDs) can have a valuable role in guiding patient management provided that concentrations are measured with a clear indication and are interpreted critically, taking into account the whole clinical context. Situations in which AED measurements are most likely to be of benefit include (1) when a person has attained the desired clinical outcome, to establish an individual therapeutic concentration which can be used at subsequent times to assess potential causes for a change in drug response; (2) as an aid in the diagnosis of clinical toxicity; (3) to assess compliance, particularly in patients with uncontrolled seizures or breakthrough seizures; (4) to guide dosage adjustment in situations associated with increased pharmacokinetic variability (e.g., children, the elderly, patients with associated diseases, drug formulation changes); (5) when a potentially important pharmacokinetic change is anticipated (e.g., in pregnancy, or when an interacting drug is added or removed); (6) to guide dose adjustments for AEDs with dose-dependent pharmacokinetics, particularly phenytoin.