Safety and tolerability of different titration rates of retigabine (ezogabine) in patients with partial-onset seizures

The art and science of drug titration

A “one-size-fits-all” approach has been the standard for drug dosing, in particular for agents with a wide therapeutic index. The scientific principles of drug titration, most commonly used for medications with a narrow therapeutic index, are to give the patient adequate and effective treatment, at the lowest dose possible, with the aim of minimizing unnecessary medication use and side effects. The art of drug titration involves the interplay of scientific drug titration principles with the clinical expertise of the healthcare provider, and an individualized, patient-centered partnership between the provider and the patient to review the delicate balance of perceived benefits and risks from both perspectives. Drug titration may occur as up-, down-, or cross-titration depending on whether the goal is to reach or maintain a therapeutic outcome, decrease the risk of adverse effects, or prevent withdrawal/discontinuation syndromes or recurrence of disease. Drug titration introduces additional complexities surrounding the conduct of clinical trials and real-world studies, confounding our understanding of the true effect of medications. In clinical practice, wide variations in titration schedules may exist due to a lack of evidence and consensus on titration approaches that achieve an optimal benefit-harm profile. Further, drug titration may be challenging for patients to follow, resulting in suboptimal adherence and may require increased healthcare-related visits and coordination of care amongst providers. Despite the challenges associated with drug titration, it is a personalized approach to drug dosing that blends science with art, and with supportive real-world outcomes-based evidence, can be effective for optimizing pharmacotherapeutic outcomes and improving drug safety.

Impact of antiepileptic-drug treatment burden on health-care-resource utilization and costs

Background

Complex titration requirements and dosing of antiepileptic drugs (AEDs) may pose a significant treatment burden for patients with epilepsy. This study evaluated health-care-resource utilization (HCRU) rates and costs by treatment burden, defined as number of daily pills and dosing frequency, among managed-care enrollees with epilepsy who initiated AED monotherapy.

Methods

This retrospective longitudinal study examined administrative HC-claim data in patients aged ≥18 years with two or more pharmacy claims for an AED and two or more medical claims for epilepsy or afebrile convulsion. The number of daily AED pills was estimated at index as the total number of pills dispensed divided by the days supplied, and categorized as more than zero/one, one/two, two/three, and more than three per day. AED-dosing frequency was measured at index and categorized as one, two, three, or four times daily. Postindex 12-month all-cause and epilepsy-related HCRU and costs were estimated using multivariable Poisson regression models and generalized linear models, respectively.

Results

Unadjusted total all-cause and epilepsy-related costs at 12 months postindex averaged US$26,015 per person and US$5,557 per person (2017 values), respectively. Adjusted all-cause and epilepsy-related costs were US$25,918 per person and US$5,602 per person, respectively. A pill burden of more than three a day was associated with a 6.7% increase in total annual HC costs compared with one pill/day. Patients receiving one/two, two/three, and more than three pills per day had 13.3%, 23.9%, and 38.3% higher epilepsy-related costs, respectively, than those receiving one pill per day (P<0.0001). Increase in dosing frequency was associated with greater total HCRU and higher costs, but only patients with twice-daily dosing had significantly higher epilepsy-related costs.

Conclusion

Findings from this study suggest that increased treatment burden is associated with greater HCRU and higher overall and epilepsy-related costs. Reducing treatment burden via selection of AED therapy with reduced pill numbers and dosing frequency should be considered to improve health and economic outcomes.

Practice guideline update summary: Efficacy and tolerability of the new antiepileptic drugs II: Treatment-resistant epilepsy: Report of the American Epilepsy Society and the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology

Objective: To update the 2004 American Academy of Neurology (AAN) guideline for managing treatment-resistant (TR) epilepsy with second- and third-generation antiepileptic drugs (AEDs). Methods: 2004 criteria were used to systematically review literature (January 2003 to November 2015), classify pertinent studies according to the therapeutic rating scheme, and link recommendations to evidence strength. Results: Forty-two articles were included. Recommendations: The following are established as effective to reduce seizure frequency (Level A): immediate-release pregabalin and perampanel for TR adult focal epilepsy (TRAFE); vigabatrin for TRAFE (not first-line treatment; rufinamide for Lennox-Gastuat syndrome (LGS) (add-on therapy). The following should be considered to decrease seizure frequency (Level B): lacosamide, eslicarbazepine, and extended-release topiramate for TRAFE (ezogabine production discontinued); immediate- and extended-release lamotrigine for generalized epilepsy with TR generalized tonic-clonic (GTC) seizures in adults; levetiracetam (add-on therapy) for TR childhood focal epilepsy (TRCFE) (1 month to 16 years), TR GTC seizures, and TR juvenile myoclonic epilepsy; clobazam for LGS (add-on therapy); zonisamide for TRCFE (6-17 years); oxcarbazepine for TRCFE (1 month to 4 years). The text presents Level C recommendations. AED selection depends on seizure/syndrome type, patient age, concomitant medications, and AED tolerability, safety, and efficacy. This evidence-based assessment informs AED prescription guidelines for TR epilepsy and indicates seizure types and syndromes needing more evidence. A recent FDA strategy allows extrapolation of efficacy across populations; therefore, for focal epilepsy, eslicarbazepine and lacosamide (oral only for pediatric use) as add-on or monotherapy in persons ≥4 years of age and perampanel as monotherapy received FDA approval.

Practice guideline update summary: Efficacy and tolerability of the new antiepileptic drugs II: Treatment-resistant epilepsy

Objective

To update the 2004 American Academy of Neurology guideline for managing treatment-resistant (TR) epilepsy with second- and third-generation antiepileptic drugs (AEDs).

Methods

2004 criteria were used to systemically review literature (January 2003 to November 2015), classify pertinent studies according to the therapeutic rating scheme, and link recommendations to evidence strength.

Results

Forty-two articles were included.

Recommendations

The following are established as effective to reduce seizure frequency (Level A): immediate-release pregabalin and perampanel for TR adult focal epilepsy (TRAFE); vigabatrin for TRAFE (not first-line treatment); rufinamide for Lennox-Gastaut syndrome (LGS) (add-on therapy). The following should be considered to decrease seizure frequency (Level B): lacosamide, eslicarbazepine, and extended-release topiramate for TRAFE (ezogabine production discontinued); immediate- and extended-release lamotrigine for generalized epilepsy with TR generalized tonic-clonic (GTC) seizures in adults; levetiracetam (add-on therapy) for TR childhood focal epilepsy (TRCFE) (1 month–16 years), TR GTC seizures, and TR juvenile myoclonic epilepsy; clobazam for LGS (add-on therapy); zonisamide for TRCFE (6–17 years); oxcarbazepine for TRCFE (1 month–4 years). The text presents Level C recommendations. AED selection depends on seizure/syndrome type, patient age, concomitant medications, and AED tolerability, safety, and efficacy. This evidence-based assessment informs AED prescription guidelines for TR epilepsy and indicates seizure types and syndromes needing more evidence. A recent Food and Drug Administration (FDA) strategy allows extrapolation of efficacy across populations; therefore, for focal epilepsy, eslicarbazepine and lacosamide (oral only for pediatric use) as add-on or monotherapy in persons ≥4 years of age and perampanel as monotherapy received FDA approval.

Influence of titration schedule and maintenance dose on the tolerability of adjunctive eslicarbazepine acetate: An integrated analysis of three randomized placebo-controlled trials

OBJECTIVE

To examine the influence of titration schedule and maintenance dose on the incidence and type of treatment-emergent adverse events (TEAEs) associated with adjunctive eslicarbazepine acetate (ESL).

METHODS

Data from three randomized, double-blind, placebo-controlled trials were analyzed. Patients with refractory partial-onset seizures were randomized to maintenance doses of ESL 400, 800, or 1200mg QD (dosing was initiated at 400 or 800mg QD) or placebo. The incidence of TEAEs was analyzed during the double-blind period (2-week titration phase; 12-week maintenance phase), according to the randomized maintenance dose and the titration schedule.

RESULTS

1447 patients were included in the analysis. During the first week of treatment, 62% of patients taking ESL 800mg QD had ≥1 TEAE, vs 35% of those taking 400mg QD and 32% of the placebo group; dizziness, somnolence, nausea, and headache were numerically more frequent in patients taking ESL 800mg than those taking ESL 400mg QD. During the double-blind period, the incidences of common TEAEs were lower in patients who initiated ESL at 400mg vs 800mg QD. For the 800 and 1200mg QD maintenance doses, rates of TEAEs leading to discontinuation were lower in patients who began treatment with 400mg than in those who began taking ESL 800mg QD.

CONCLUSIONS

Initiation of ESL at 800mg QD is feasible. However, initiating treatment with ESL 400mg QD for 1 or 2 weeks is recommended, being associated with a lower incidence of TEAEs, and related discontinuations. For some patients, treatment may be initiated at 800mg QD, if the need for more immediate seizure reduction outweighs concerns about increased risk of adverse reactions during initiation.

Tolerability of new antiepileptic drugs: a network meta-analysis

OBJECTIVE

The objective of this study was to perform a comparative assessment of tolerability of all licensed new antiepileptic drugs (AEDs) through a network meta-analysis (NMA) including all placebo-controlled double-blind clinical trials (RCTs) in all conditions in which these drugs have been tested.

METHODS

NMA with a frequentist approach was used to compare proportions of patients withdrawing because of adverse events (AEs). Analyses were conducted for all therapeutic doses pooled and specifically for high therapeutic doses. Patients treated with non-therapeutic doses of each drug were excluded.

RESULTS

A total of 195 RCTs were included in the current analysis, comprising a total of 28,013 patients treated with AEDs and 17,908 patients treated with placebo. RCTs included in the analysis were 8 for brivaracetam; 5 for eslicarbazepine; 22 for gabapentin; 7 for lacosamide; 14 for levetiracetam; 14 for lamotrigine; 6 for oxcarbazepine; 9 for perampanel; 50 for pregabalin; 5 for tiagabine; 36 for topiramate; 7 for zonisamide; 4 for gabapentin-extended formulation (ER); 2 each for levetiracetam-ER, lamotrigine-ER, and topiramate-ER; and 1 each for oxcarbazepine-ER and pregabalin-ER. Brivaracetam, gabapentin, gabapentin-ER, and levetiracetam had a significantly lower withdrawal rate compared to several other AEDs, while eslicarbazepine, lacosamide, oxcarbazepine, and topiramate had a higher withdrawal rate. Perampanel, lamotrigine, pregabalin, tiagabine, and zonisamide showed an intermediate pattern of tolerability. Additional analysis has been conducted through selection of highly recommended doses for each drug. This analysis has roughly confirmed results of head to head comparisons of the all-dose analysis, with some exceptions. A further analysis has been conducted after exclusion of RCTs in which patients were allocated to the therapeutic dose of the experimental drug without titration, and it failed to show clinically important differences.

SIGNIFICANCE

Relevant differences in short-term tolerability of AEDs have been observed between AEDs. Brivaracetam, gabapentin, and levetiracetam show the best tolerability profile while other AEDs are at higher risk for intolerable adverse effects.

The anticonvulsant retigabine suppresses neuronal KV2-mediated currents

Enhancement of neuronal M-currents, generated through K_V7.2-K_V7.5 channels, has gained much interest for its potential in developing treatments for hyperexcitability-related disorders such as epilepsy. Retigabine, a K_V7 channel opener, has proven to be an effective anticonvulsant and has recently also gained attention due to its neuroprotective properties. In the present study, we found that the auxiliary KCNE2 subunit reduced the K_V7.2-K_V7.3 retigabine sensitivity approximately 5-fold. In addition, using both mammalian expression systems and cultured hippocampal neurons we determined that low μM retigabine concentrations had ‘off-target’ effects on K_V2.1 channels which have recently been implicated in apoptosis. Clinical retigabine concentrations (0.3–3 μM) inhibited K_V2.1 channel function upon prolonged exposure. The suppression of the K_V2.1 conductance was only partially reversible. Our results identified K_V2.1 as a new molecular target for retigabine, thus giving a potential explanation for retigabine’s neuroprotective properties.

Antiepileptic drugs in development pipeline: A recent update

Epilepsy is the most common neurological disorder which significantly affects the quality of life and poses a health as well as economic burden on society. Epilepsy affects approximately 70 million people in the world. The present article reviews the scientific rationale, brief pathophysiology of epilepsy and newer antiepileptic drugs which are presently under clinical development. We have searched the investigational drugs using the key words ‘antiepileptic drugs,’ ‘epilepsy,’ ‘Phase I,’ ‘Phase II’ and ‘Phase III’ in American clinical trial registers (clinicaltrials.gov), the relevant published articles using National Library of Medicine's PubMed database, company websites and supplemented results with a manual search of cross-references and conference abstracts. This review provides a brief description about the antiepileptic drugs which are targeting different mechanisms and the clinical development status of these drugs. Besides the presence of old as well as new AEDs, still there is a need of new drugs or the modified version of old drugs in order to make affected people free of seizures. An optimistic approach should be used to translate the success of preclinical testing to clinical practice. There is an urgent need to improve animal models and to explore new targets with better understanding in order to develop the novel drugs with more efficacy and safety.

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This review primarily focused on antiepileptic drugs under clinical development.

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The more realistic approach is needed to discover and develop the novel antiepileptic drugs.

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Modification of conventional drugs or search of newer targets can lead to development of promising antiepileptic drugs.

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To develop more efficacious and safe drugs for treatment of epilepsy and refractory seizures

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There are a number of novel antiepileptic compounds which are under various stages of drug development.

New antiepileptic drugs: focus on ezogabine, clobazam, and perampanel

Ezogabine, clobazam, and perampanel are among the newest antiseizure drugs approved by the Food and Drug Administration between 2011 and 2012. Ezogabine and perampanel are approved for adjunctive treatment of partial epilepsy. Perampanel is also approved for adjunctive treatment of primary generalized tonic–clonic seizures. Ezogabine and perampanel have novel mechanisms of action. Ezogabine binds to voltage-gated potassium channels and increases the M-current thereby causing membrane hyperpolarization. Perampanel is a selective, non-competitive 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid receptor antagonist, which reduces neuronal excitation. Clobazam has been used worldwide since the 1970s and is approved for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome. Clobazam is the only 1,5-benzodiazepine currently in clinical use, which is less sedating than the commonly used 1,4-benzodiazepines. Phase III multicenter, randomized, double-blind, placebo-controlled trials demonstrated efficacy and good tolerability of these 3 new antiepileptic drugs. These drugs represent a welcome addition to the armamentarium of practitioners, but it remains to be seen how they will affect the landscape of pharmacoresistant epilepsy.

Efficacy and safety of ezogabine/retigabine as adjunctive therapy to specified single antiepileptic medications in an open-label study of adults with partial-onset seizures

PURPOSE

To assess efficacy/tolerability of ezogabine (EZG)/retigabine (RTG) in combination with specified monotherapy antiepileptic drug (AED) treatments in adults with uncontrolled partial-onset seizures using a flexible dosing regimen.

METHODS

NCT01227902 was an open-label, uncontrolled study of flexibly dosed EZG/RTG. Adults with partial-onset seizures must have been taking either carbamazepine/oxcarbazepine (CBZ/OXC), lamotrigine (LTG), levetiracetam (LEV), or valproic acid (VPA). The study comprised a screening/baseline phase, a 4-week titration phase (initiation on 150mg/day [50mg three times daily (TID)] with weekly increases of 150mg/day [50mg TID] over 4 weeks to 600mg/day), and a flexible dose evaluation (FDE) phase (optional weekly dose changes of 50-150mg/day, to an optimal daily dosage [300-1200mg/day]). The primary efficacy endpoint was percentage of patients experiencing a ≥50% reduction from baseline in partial seizure frequency (responder rate) during the treatment phase (titration and FDE phases). Safety and tolerability were also assessed.

RESULTS

Patients (N=203) were enrolled and received ≥1 dose of EZG/RTG. The dose of EZG/RTG prescribed most frequently during the treatment phase was 600mg/day for all AED groups. Responder rates during the treatment phase were: 40.0% (CBZ/OXC), 32.0% (LTG), 50.0% (LEV), and 56.9% (VPA). Treatment-emergent adverse events occurred in 82% (CBZ/OXC), 76% (LTG), 73% (LEV), and 67% (VPA) of patients; most were of mild-to-moderate intensity.

CONCLUSIONS

EZG/RTG was effective as adjunctive therapy to CBZ/OXC, LTG, LEV, and VPA, using a flexible dosing regimen, in adults with partial-onset seizures; safety and tolerability were consistent with that previously observed.

New antiepileptic medication linked to blue discoloration of the skin and eyes

Ezogabine is an antiepileptic medication approved in June 2011 by the US Food and Drug Administration (FDA) as an adjunctive treatment for partial seizures. Minimal drug interactions and a novel mechanism of action made ezogabine an appealing new treatment option. However, adverse effects reported during clinical trials and following drug approval have been alarming. A Risk Evaluation Mitigation Strategy (REMS) program has been established for urinary retention. A safety alert was published in April 2013 warning ezogabine may cause retinal pigment abnormalities and/or blue-gray discoloration, most notably on or near the lips, nail beds, sclera and conjunctiva with long-term use. In October 2013, the FDA announced a formal label change to ezogabine to include a black boxed warning emphasizing the previously reported warnings of eye and skin discoloration and permanent vision changes. Given the unknown nature of the pathophysiology, consequences and potential for reversibility of these effects, GlaxoSmithKline and the FDA have published recommendations for patients currently receiving ezogabine. Further data from published case reports and long-term safety trials in the future may lend additional insight into these concerning effects.

Drug-induced cerebellar ataxia: a systematic review

BACKGROUND AND OBJECTIVES

Cerebellar ataxia can be induced by a large number of drugs. We here conducted a systemic review of the drugs that can lead to cerebellar ataxia as an adverse drug reaction (ADR).

METHODS

We performed a systematic literature search in Pubmed (1966 to January 2014) and EMBASE (1988 to January 2014) to identify all of the drugs that can have ataxia as an ADR and to assess the frequency of drug-induced ataxia for individual drugs. Furthermore, we collected reports of drug-induced ataxia over the past 20 years in the Netherlands by querying a national register of ADRs.

RESULTS

Drug-induced ataxia was reported in association with 93 individual drugs (57 from the literature, 36 from the Dutch registry). The most common groups were antiepileptic drugs, benzodiazepines, and antineoplastics. For some, the number needed to harm was below 10. Ataxia was commonly reversible, but persistent symptoms were described with lithium and certain antineoplastics.

CONCLUSIONS

It is important to be aware of the possibility that ataxia might be drug-induced, and for some drugs the relative frequency of this particular ADR is high. In most patients, symptoms occur within days or weeks after the introduction of a new drug or an increase in dose. In general, ataxia tends to disappear after discontinuation of the drug, but chronic ataxia has been described for some drugs.

Highights in the history of epilepsy: the last 200 years

The purpose of this study was to present the evolution of views on epilepsy as a disease and symptom during the 19th and the 20th century. A thorough study of texts, medical books, and reports along with a review of the available literature in PubMed was undertaken. The 19th century is marked by the works of the French medical school and of John Hughlings Jackson who set the research on epilepsy on a solid scientific basis. During the 20th century, the invention of EEG, the advance in neurosurgery, the discovery of antiepileptic drugs, and the delineation of underlying pathophysiological mechanisms, were the most significant advances in the field of research in epilepsy. Among the most prestigious physicians connected with epilepsy one can pinpoint the work of Henry Gastaut, Wilder Penfield, and Herbert Jasper. The most recent advances in the field of epilepsy include the development of advanced imaging techniques, the development of microsurgery, and the research on the connection between genetic factors and epileptic seizures.