Truly "rational" polytherapy: maximizing efficacy and minimizing drug interactions, drug load, and adverse effects

Systematic Adverse Drug Reaction Monitoring of Patients Under Newer Antiepileptic Drugs Using Routine Clinical Data of Inpatients

BACKGROUND

Based on data of clinical trials, new agents are receiving approval to the pharmaceutical market, for which information concerning safety issues under real-life conditions is not yet available.

OBJECTIVES

The aim was to evaluate the tolerability of newer antiepileptic drugs (AEDs), such as topiramate, levetiracetam, zonisamide, pregabalin, extended-release oxcarbazepine, lacosamide and eslicarbazepine, under real-life conditions by means of an assessment of routine clinical data of inpatients.

METHOD

Over 2.75 years data of all inpatients receiving one of the newer AEDs were documented. Occurring adverse drug reactions (ADRs) were classified according to the WHO-UMC Causality Assessment concerning their likely relationship to the prescribed AEDs. For each AED, the total number of patients without and with ADRs, assessed as at least possibly related to the particular drug, was calculated and corresponding incidences compared with reference data provided in the Summary of Product Characteristics (SmPC). For statistical evaluation Spearman correlation (rs), estimated relative risk and logistic regression analysis were used.

RESULTS

In total, the data of 562 patients were assessed, of which 90 % received up to six different AEDs. The proportion of off-label use with regard to dosage varied between 6.4 and 64.7 %. Levetiracetam and oxcarbazepine as an extended-release formulation were most commonly used, and levetiracetam showed the best tolerance. By using logistic regression, the occurrence of ADRs was significantly associated with the number of AEDs (p < 0.001) as well as the defined daily doses (p = 0.003). In total, ADRs of AEDs were documented for 318 patients (56.6 %). The most common referred to electrolyte imbalance, e.g., low sodium (n = 79, 14.1 %) and potassium (n = 25, 4.4 %) levels, the central nervous system, including dizziness (n = 61, 10.9 %), disturbed vision (n = 47, 8.4 %), fatigue (n = 40, 7.1 %), nystagmus (n = 36, 6.4 %) and ataxia (n = 29, 5.2 %), or cognitive deficits, especially disturbance of speech (n = 37, 6.6 %), memory impairment (n = 36, 6.4 %) and mental slowing (n = 32, 5.7 %). By comparing the assessed ADR incidences with specification data, for some ADRs, a probable underestimation by the SmPC of respective risk could be assumed.

CONCLUSION

During inpatient treatment, valuable data are generated, which are currently rarely utilized for pharmacoepidemiologic or pharmacovigilance purposes. A systematic evaluation of these data can increase the probability of detecting ADRs and can promote real-life-related drug surveillance.

Multiple anti-epileptic drug use in children with epilepsy in Mulago hospital, Uganda: a cross sectional study

BACKGROUND

Seizures in up to one third of children with epilepsy may not be controlled by the first anti-epileptic drug (AED). In this study, we describe multiple AED usage in children attending a referral clinic in Uganda, the factors associated with multiple AED use and seizure control in affected patients.

METHODS

One hundred thirty nine patients attending Mulago hospital paediatric neurology clinic with epilepsy and who had been on AEDs for ≥6 months were consecutively enrolled from July to December 2013 to reach the calculated sample size. With consent, the history and physical examination were repeated and the neurophysiologic and imaging features obtained from records. Venous blood was also drawn to determine AED drug levels. We determined the proportion of children on multiple AEDs and performed regression analyses to determine factors independently associated with multiple AED use.

RESULTS

Forty five out of 139 (32.4 %) children; 46.7 % female, median age 6 (IQR = 3-9) years were on multiple AEDs. The most common combination was sodium valproate and carbamazepine. We found that 59.7 % of children had sub-therapeutic drug levels including 42.2 % of those on multi-therapy. Sub-optimal seizure control (adjusted odds ratio [OR(a)] 3.93, 95 % CI 1.66-9.31, p = 0.002) and presence of focal neurological deficits (OR(a) 3.86, 95 % CI 1.31-11.48, p = 0.014) were independently associated with multiple AED use but not age of seizure onset, duration of epilepsy symptoms, seizure type or history of status epilepticus.

CONCLUSION

One third of children with epilepsy in Mulago receive multiple AEDs. Multiple AED use is most frequent in symptomatic focal epilepsies but doses are frequently sub-optimal. There is urgent need to improve clinical monitoring in our patients.

CRISPR/Cas9 facilitates investigation of neural circuit disease using human iPSCs: mechanism of epilepsy caused by an SCN1A loss-of-function mutation

Mutations in SCN1A, the gene encoding the α subunit of Nav1.1 channel, can cause epilepsies with wide ranges of clinical phenotypes, which are associated with the contrasting effects of channel loss-of-function or gain-of-function. In this project, CRISPR/Cas9- and TALEN-mediated genome-editing techniques were applied to induced pluripotent stem cell (iPSC)-based-disease model to explore the mechanism of epilepsy caused by SCN1A loss-of-function mutation. By fluorescently labeling GABAergic subtype in iPSC-derived neurons using CRISPR/Cas9, we for the first time performed electrophysiological studies on SCN1A-expressing neural subtype and monitored the postsynaptic activity of both inhibitory and excitatory types. We found that the mutation c.A5768G, which led to no current of Nav1.1 in exogenously transfected system, influenced the properties of not only Nav current amount, but also Nav activation in Nav1.1-expressing GABAergic neurons. The two alterations in Nav further reduced the amplitudes and enhanced the thresholds of action potential in patient-derived GABAergic neurons, and led to weakened spontaneous inhibitory postsynaptic currents (sIPSCs) in the patient-derived neuronal network. Although the spontaneous excitatory postsynaptic currents (sEPSCs) did not change significantly, when the frequencies of both sIPSCs and sEPSCs were further analyzed, we found the whole postsynaptic activity transferred from the inhibition-dominated state to excitation in patient-derived neuronal networks, suggesting that changes in sIPSCs alone were sufficient to significantly reverse the excitatory level of spontaneous postsynaptic activity. In summary, our findings fill the gap of our knowledge regarding the relationship between SCN1A mutation effect recorded on exogenously transfected cells and on Nav1.1-expressing neurons, and reveal the physiological basis underlying epileptogenesis caused by SCN1A loss-of-function mutation.

A prospective study of adverse drug reactions to antiepileptic drugs in children

OBJECTIVES

To prospectively determine the nature and rate of adverse drug reactions (ADRs) in children on antiepileptic drugs (AEDs) and to prospectively evaluate the effect of AEDs on behaviour.

SETTING

A single centre prospective observational study.

PARTICIPANTS

Children (<18 years old) receiving one or more AEDs for epilepsy, at each clinically determined follow-up visit.

PRIMARY AND SECONDARY OUTCOMES

Primary outcome was adverse reactions of AEDs. Behavioural and cognitive functions were secondary outcomes.

RESULTS

180 children were recruited. Sodium valproate and carbamazepine were the most frequently used AEDs. A total of 114 ADRs were recorded in 56 of these children (31%). 135 children (75%) were on monotherapy. 27 of the 45 children (60%) on polytherapy had ADRs; while 29 (21%) of those on monotherapy had ADRs. The risk of ADRs was significantly lower in patients receiving monotherapy than polytherapy (RR: 0.61, 95% CI 0.47 to 0.79, p<0.0001). Behavioural problems and somnolence were the most common ADRs. 23 children had to discontinue their AED due to an ADR.

CONCLUSIONS

Behavioural problems and somnolence were the most common ADRs. Polytherapy significantly increases the likelihood of ADRs in children.

TRAIL REGISTRATION NUMBER

EudraCT (2007-000565-37).

Perampanel efficacy and tolerability with enzyme-inducing AEDs in patients with epilepsy

OBJECTIVE

Evaluate the impact of concomitant enzyme (CYP3A4)-inducer antiepileptic drugs (EIAEDs) on the efficacy and safety of perampanel in patients from the 3 phase-III clinical trials.

METHODS

Patients with pharmacoresistant partial-onset seizures in the 3 phase-III clinical studies were aged 12 years and older and receiving 1 to 3 concomitant antiepileptic drugs. Following 6-week baseline, patients were randomized to once-daily, double-blind treatment with placebo or perampanel 8 or 12 mg (studies 304 and 305) or placebo or perampanel 2, 4, or 8 mg (study 306).

RESULTS

Treatment response assessed by median percent reduction in seizure frequency and responder rates improved with perampanel compared with placebo. However, at 8 and 12 mg, the treatment response was significantly greater in patients receiving non-EIAEDs. The treatment effect (perampanel-placebo) also demonstrated a dose-dependent increase in all patients. The overall incidence of treatment-emergent adverse events was similar regardless of the presence of EIAEDs. Occurrence of some adverse events, such as fatigue, somnolence, dizziness, irritability, was greater in patients receiving non-EIAEDs, as was discontinuation because of adverse events.

CONCLUSIONS

Perampanel shows efficacy and safety in the presence and absence of EIAEDs. As systemic exposure to perampanel increases, so does efficacy. Given the extensive metabolism of perampanel, systemic exposure is clearly reduced with concomitant administration of CYP3A4 inducers. This supports the strategy of dosing perampanel to clinical effect. Recognition of these pharmacokinetic interactions will be important in the optimization of this novel medication.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that 2 to 12 mg/d doses of perampanel reduced seizure frequency and improved responder rate in the presence and absence of EIAEDs.

Eslicarbazepine acetate for the treatment of focal epilepsy: an update on its proposed mechanisms of action

Eslicarbazepine acetate (ESL) is a once daily antiepileptic drug (AED) approved by the European Medicines Agency (EMA), the Food and Drug Administration (FDA) and Health Canada as an adjunctive therapy in adults with partial-onset seizures (POS). In humans and in relevant animal laboratory species, ESL undergoes extensive first pass hydrolysis to its major active metabolite eslicarbazepine that represents ∼95% of circulating active moieties. ESL and eslicarbazepine showed anticonvulsant activity in animal models. ESL may not only suppress seizure activity but may also inhibit the generation of a hyperexcitable network. Data reviewed here suggest that ESL and eslicarbazepine demonstrated the following in animal models: (1) the selectivity of interaction with the inactive state of the voltage-gated sodium channel (VGSC), (2) reduction in VGSC availability through enhancement of slow inactivation, instead of alteration of fast inactivation of VGSC, (3) the failure to cause a paradoxical upregulation of persistent Na⁺ current (I_NaP), and (4) the reduction in firing frequencies of excitatory neurons in dissociated hippocampal cells from patients with epilepsy who were pharmacoresistant to carbamazepine (CBZ). In addition, eslicarbazepine effectively inhibited high- and low-affinity hCa_V3.2 inward currents with greater affinity than CBZ. These preclinical findings may suggest the potential for antiepileptogenic effects; furthermore, the lack of effect upon K_V7.2 outward currents may translate into a reduced potential for eslicarbazepine to facilitate repetitive firing.

Combined diazepam and MK-801 therapy provides synergistic protection from tetramethylenedisulfotetramine-induced tonic-clonic seizures and lethality in mice

The synthetic rodenticide, tetramethylenedisulfotetramine (TMDT), is a persistent and highly lethal GABA-gated Cl(-) channel blocker. TMDT is clandestinely produced, remains popular in mainland China, and causes numerous unintentional and deliberate poisonings worldwide. TMDT is odorless, tasteless, and easy to manufacture, features that make it a potential weapon of terrorism. There is no effective treatment. We previously characterized the effects of TMDT in C57BL/6 mice and surveyed efficacies of GABAergic and glutamatergic anticonvulsant treatments. At 0.4 mg/kg i.p., TMDT produced neurotoxic symptomatology consisting of twitches, clonic and tonic-clonic seizures, often progressing to status epilepticus and death. If administered immediately after the occurrence of the first clonic seizure, the benzodiazepine diazepam (DZP) effectively prevented all subsequent seizure symptoms, whereas the NMDA receptor antagonist dizocilpine (MK-801) primarily prevented tonic-clonic seizures. The latter agent, however, appeared to be more effective at preventing delayed death. The present study further explored these phenomena, and characterized the therapeutic actions of DZP and MK-801 as combinations. Joint treatment with both DZP and MK-801 displayed synergistic protection against tonic-clonic seizures and 24 h lethality as determined by isobolographic analysis. Clonic seizures, however, remained poorly controlled. A modification of the treatment regimen, where DZP was followed 10 min later by MK-801, yielded a reduction in both types of seizures and improved overall outcome. Simultaneous monitoring of subjects via EEG and videography confirmed effectiveness of this sequential regimen. We conclude that TMDT blockage at GABAA receptors involves early activation of NMDA receptors, which contribute to persistent ictogenic activity. Our data predict that a sequential combination treatment with DZP followed by MK-801 will be superior to either individual therapy with, or simultaneous administration of, these two agents in treating TMDT poisoning.

Standard dose valproic acid does not cause additional cognitive impact in a rodent model of intractable epilepsy

Children with epilepsy face significant cognitive and behavioral impairments. These impairments are due to a poorly characterized interaction between the underlying etiology, the effect of seizures and the effect of medication. The large variation in these factors make understanding the main drivers of cognitive impairment in humans extremely difficult. Therefore, we investigated the cognitive effect of seizures and the antiepileptic drug valproic acid in a rodent model of cortical dysplasia. Rats were divided into seizure-receiving and non-receiving groups. Rats experienced frequent early life seizures using the flurothyl inhalation method: 50 seizures between postnatal day 5 and 15 and then one seizure a day following that. Rats were further divided into drug-treated and vehicle treated groups. Valproic acid treated animals were treated from 5 days preceding behavioral testing in the Morris water maze at a clinically relevant concentration. We show here that the main driver of cognitive impairments are the brain malformations, and that persistent seizures in animals with brain malformations and valproic acid caused no additional impact. These findings suggest that neither an appropriate dose of a standard antiepileptic drug or intractable seizures worsen cognition associated with a malformation of cortical development and that alternative treatment strategies to improve cognition are required.

Melatonin therapy for REM sleep behavior disorder: a critical review of evidence

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia associated with dream enactment often involving violent or potentially injurious behaviors during REM sleep that is strongly associated with synucleinopathy neurodegeneration. Clonazepam has long been suggested as the first-line treatment option for RBD. However, evidence supporting melatonin therapy is expanding. Melatonin appears to be beneficial for the management of RBD with reductions in clinical behavioral outcomes and decrease in muscle tonicity during REM sleep. Melatonin also has a favorable safety and tolerability profile over clonazepam with limited potential for drug-drug interactions, an important consideration especially in elderly individuals with RBD receiving polypharmacy. Prospective clinical trials are necessary to establish the evidence basis for melatonin and clonazepam as RBD therapies.

Drug utilization in pediatric neurology outpatient department: A prospective study at a tertiary care teaching hospital

Background:

Neurological disorders are a significant cause of morbidity, mortality and adversely affect quality of life among pediatric patients. In India, more than 30% population is under 20 years of age, many of whom present late during the course of illness. Several drugs prescribed to pediatric population suffering from neurological disorders may be off label or unlicensed.

Aims and Objectives:

To study drug use pattern, identify off-label/unlicensed drug use and to check potential for drug-drug interactions in patients attending outpatient department of pediatric neurology at a tertiary care teaching hospital.

Methodology:

Prescriptions of patients attending pediatric neurology outpatient department were collected prospectively for 8 weeks. They were analyzed for prescribing pattern, WHO core prescribing indicators, off-label/unlicensed drug use and potential for drug-drug interactions.

Result:

A total of 140 prescriptions were collected, male female ratio being 2:1. Epilepsy was the most common diagnosis (73.57%) followed by breath holding spells, migraine and developmental disorders. Partial seizure was the most common type of epilepsy (52.42%). Average number of drugs prescribed per patient was 1.56. Most commonly prescribed drug was sodium valproate (25.11%) followed by phenytoin (11.41%). About 16% of the prescriptions contained newer antiepileptic drugs. More than 60% of the drugs were prescribed from WHO essential drug list. In 8.57% of cases drugs were prescribed in off-label/unlicensed manner. Twenty-six percent prescriptions showed potential for drug interactions.

Conclusion:

Epilepsy is the most common neurological disease among children and adolescents. Sodium valproate is the most commonly prescribed drug. A few prescriptions contained off-label/unlicensed drugs.

Who receives home-based perinatal palliative care: experience from Poland

Context. The current literature suggests that perinatal palliative care (PPC) programs should be comprehensive, initiated early, and integrative. So far there have been very few publications on the subject of home-based PC of newborns and neonates. Most publications focus on hospital-based care, mainly in the neonatal intensive care units. Objective. To describe the neonates and infants who received home-based palliative care in Lodz Region between 2005 and 2011. Methods. A retrospective review of medical records. Results. 53 neonates and infants were admitted to a home hospice in Lodz Region between 2005 and 2011. In general, they are a growing group of patients referred to palliative care. Congenital diseases (41%) were the primary diagnoses; out of 53 patients 16 died, 20 were discharged home, and 17 stayed under hospice care until 2011. The most common cause of death (56%) was cardiac insufficiency. Neurological symptoms (72%) and dysphagia (58%) were the most common clinical problems. The majority of children (45%) had a feeding tube inserted and were oxygen dependent (45%); 39 families received psychological care and 31 social supports. Conclusions. For terminally ill neonates and infants, perinatal palliative care is an option which improves the quality of their lives and provides the family with an opportunity to say goodbye.

When one plus one makes three: the quest for rational antiepileptic polytherapy with supraadditive anticonvulsant efficacy

The experimental and clinical evidence in support of "rational polytherapy" is sparse, and to date, no clear evidence-based indications can be made to help physicians in their choice of a specific drug combination against specific forms of epilepsy. This article briefly reviews the data available in the literature and obtained from studies conducted in humans to evaluate which main AED combinations might possess supraadditive, synergistic effects in terms of efficacy, with infraadditive toxicity. By far, the most documented association resulting in supraadditive anticonvulsant effects against focal seizures is that of VPA and LTG. There are some indications that combinations of drugs with different primary mechanisms of action may be more effective than combining drugs with the same mechanisms of action. However, further animal and human research studies that focus both on toxicity and anticonvulsant effects of various combinations of AEDs are required.

Seizure treatment in transplant patients

OPINION STATEMENT

Solid organ transplantation is frequently complicated by a spectrum of seizure types, including single partial-onset or generalized tonic-clonic seizures, acute repetitive seizures or status epilepticus, and sometimes the evolution of symptomatic epilepsy. There is currently no specific evidence involving the transplant patient population to guide the selection, administration, or duration of antiepileptic drug (AED) therapy, so familiarity with clinical AED pharmacology and application of sound judgment are necessary for successful patient outcomes. An initial detailed search for symptomatic seizure etiologies, including metabolic, infectious, cerebrovascular, and calcineurin inhibitor treatment-related neurotoxic complications such as posterior reversible encephalopathy syndrome (PRES), is imperative, as underlying central nervous system disorders may impose additional serious risks to cerebral or general health if not promptly detected and appropriately treated. The mainstay for post-transplant seizure management is AED therapy directed toward the suspected seizure type. Unfavorable drug interactions could place the transplanted organ at risk, so choosing an AED with limited interaction potential is also crucial. When the transplanted organ is dysfunctional or vulnerable to rejection, AEDs without substantial hepatic metabolism are favored in post-liver transplant patients, whereas after renal transplantation, AEDs with predominantly renal elimination may require dosage adjustment to prevent adverse effects. Levetiracetam, gabapentin, pregabalin, and lacosamide are drugs of choice for treatment of partial-onset seizures in post-transplant patients given their efficacy spectrum, generally excellent tolerability, and lack of drug interaction potential. Levetiracetam is the drug of choice for primary generalized seizures in post-transplant patients. When intravenous drugs are necessary for acute seizure management, benzodiazepines and fosphenytoin are the traditional and best evidence-based options, although intravenous levetiracetam, valproate, and lacosamide are emerging options. Availability of several newer AEDs has greatly expanded the therapeutic armamentarium for safe and efficacious treatment of post-transplant seizures, but future prospective clinical trials and pharmacokinetic studies within this specific patient population are needed.

Antiepileptic drug monotherapy versus polytherapy: pursuing seizure freedom and tolerability in adults

PURPOSE OF REVIEW

Despite the availability of many new antiepileptic drugs (AEDs), only around 50% of people with epilepsy will become seizure free on their first drug. This article explores treatment options and issues influencing whether AEDs should be substituted or combined in the remainder of the patient population.

RECENT FINDINGS

Prior to the introduction of novel AEDs, it was generally opined that combining traditional agents did not necessarily lead to an improvement in seizure control and might increase the propensity for side effects. Newer AEDs, many with different mechanisms of action, have increased the potential for polytherapy regimens, although robust data to support or refute this therapeutic strategy are sparse. It seems sensible to substitute rather than combine when the first AED produces an idiosyncratic reaction, is poorly tolerated at a low/moderate dose or shows no efficacy. Polytherapy may be preferred if the patient tolerates their first or second AED well, but with a suboptimal response, particularly when there is an identifiable anatomical substrate for the seizures. AED selection requires consideration of many factors some of which are discussed in this study.

SUMMARY

There are no definitive answers on whether to combine or substitute AEDs. Different strategies are required for different scenarios in different patients.

The impact of background antiepileptic drugs on the efficacy and safety of pregabalin in treating partial-onset seizures: a post hoc analysis of combined clinical trials

Pregabalin is used as adjunctive treatment for partial-onset seizures and is often combined with multiple antiepileptic drugs (AEDs) from different classes. The objectives of this post hoc analysis were to evaluate the efficacy and safety of pregabalin when added to different AED regimens and to identify specific AED combinations that in conjunction with pregabalin yield high responder rates. Data from six double-blind, randomized studies of pregabalin in patients with partial-onset seizures were pooled for analysis (N=1775). When the treatment groups (placebo, 150mg, 300mg, 600mg, and flexible dose) were stratified by the number of concomitant AEDs (one, two or three or more), modeling results suggested that the magnitude of improvement on either ≥50% responder rate or mean response ratio remained consistent regardless of the number of concomitant AEDs. Adverse events were typical of pregabalin and, in general, did not vary as the number of concomitant AEDs increased. A cluster analysis was performed to identify possible combinations of AEDs that yielded high ≥50% responder rates. The majority of patients (>90%) fell within two clusters that yielded high responder rates, while <10% of the patients fell within two clusters that yielded low responder rates. Numerous AED combinations, ranging from 6 to 11, occurred within each cluster. In summary, pregabalin provided a consistent improvement in seizure reduction and comparable tolerability in patients with partial-onset epilepsy regardless of the number of concomitant AEDs.

Combining antiepileptic drugs--rational polytherapy?

The global introduction of 14 new antiepileptic drugs (AEDs) over the past 20 years as adjunctive treatment in refractory epilepsy has triggered an increased interest in optimising combination therapy. With a widening range of available mechanisms of AED action, much activity has been focused on the defining and refining "rational polytherapy" with AEDs that have differing pharmacological properties. This paper reviews the available animal and human data exploring this issue. The experimental and clinical evidence in support of "rational polytherapy" is sparse, with only the combination of sodium valproate with lamotrigine demonstrating synergism. Robust evidence to guide clinicians on how and when to combine AEDs is lacking and current practice recommendations are largely empirical. Practical guidance for the clinician is summarised and discussed in this review. In particular, care should be taken to avoid excessive drug load, which can be associated with decreased tolerability and, therefore, reduced likelihood of seizure freedom. A palliative strategy should be defined early for the more than 30% of patients with refractory epilepsy. Nevertheless, the availability of an increasing number of pharmacologically distinct AEDs has produced a modest improvement in prognosis with combination therapy, which will encourage the clinician to persevere with continued pharmacological manipulation when other therapeutic options have been tried or are not appropriate.

Interactions between modulators of the GABA(A) receptor: Stiripentol and benzodiazepines

Many patients with refractory epilepsy are treated with polytherapy, and nearly 15% of epilepsy patients receive two or more anti-convulsant agents. The anti-convulsant stiripentol is used as an add-on treatment for the childhood epilepsy syndrome known as severe myoclonic epilepsy in infancy (Dravet syndrome). Stiripentol has multiple mechanisms of action, both enhancing GABA(A) receptors and reducing activity of metabolic enzymes that break down other drugs. Stiripentol is typically co-administered with other anti-convulsants such as benzodiazepines which also act through GABA(A) receptor modulation. Stiripentol slows the metabolism of some of these drugs through inhibition of a variety of cytochrome P450 enzymes, but could also influence their effects on GABAergic neurotransmission. Is it rational to co-administer drugs which can act through the same target? To examine the potential interaction between these modulators, we transiently transfected HEK-293T cells to produce α3β3γ2L or α3β3δ recombinant GABA(A) receptors. Using whole-cell patch clamp recordings, we measured the response to each benzodiazepine alone and in combination with a maximally effective concentration of stiripentol. We compared the responses to four different benzodiazepines: diazepam, clonazepam, clobazam and norclobazam. In all cases we found that these modulators were equally effective in the presence and absence of stiripentol. The δ-containing receptors were insensitive to modulation by the benzodiazepines, which did not affect potentiation by stiripentol. These data suggest that stiripentol and the benzodiazepines act independently at GABA(A) receptors and that polytherapy could be expected to increase the maximum effect beyond either drug alone, even without consideration of changes in metabolism.

A pooled analysis of lacosamide clinical trial data grouped by mechanism of action of concomitant antiepileptic drugs

BACKGROUND

Lacosamide, a new antiepileptic drug (AED) with a different pharmacological action that enhances sodium channel slow inactivation, is approved for the adjunctive treatment of partial-onset seizures in adults. Previous analyses of pooled phase II/III trials have demonstrated that lacosamide provides additional efficacy when added to a broad range of AEDs.

OBJECTIVE

To further evaluate the efficacy and safety of lacosamide by grouping patients based upon the sodium channel-blocking properties of their concomitant AEDs.

STUDY DESIGN

Post hoc exploratory analyses were performed on pooled data in which patients were grouped based upon inclusion or non-inclusion of at least one 'traditional' sodium channel-blocking AED (defined as carbamazepine, lamotrigine, oxcarbazepine and phenytoin derivatives) as part of their concomitant AED regimen.

SETTING

Data pooled from previously conducted phase II/III clinical trials of lacosamide.

PATIENTS

Adult patients with partial-onset seizures with or without secondary generalization (N = 1308).

INTERVENTION

Four- to six-week Titration Phase followed by 12-week maintenance treatment with adjunctive lacosamide (Vimpat®) [200, 400 or 600 mg/day] or placebo.

MAIN OUTCOME MEASURE

Efficacy variables included change in seizure frequency per 28 days and the proportion of patients experiencing a ≥50% reduction in seizure frequency (50% responder rate) from Baseline to the Maintenance Phase. The proportion of patients experiencing a ≥75% reduction in seizure frequency from Baseline to the Maintenance Phase (75% responder rate) was also assessed. Safety parameters assessed were treatment-emergent adverse events (TEAEs) and discontinuation due to TEAEs. Additional safety assessments were changes in ECG and laboratory parameters as well as vital signs (including bodyweight).

RESULTS

Of 1308 patients in the pooled phase II/III population, the majority (82%) were using at least one 'traditional' sodium channel-blocking concomitant AED. In this subgroup of patients, adjunctive lacosamide showed significant reductions in seizure frequency (p < 0.01, all dosages) and significantly greater 50% and 75% responder rates (p < 0.01 for 400 mg/day; p < 0.01 [50% responder rate] and p < 0.05 [75% responder rate] for 600 mg/day) compared with placebo; these effects were similar to the results seen in the pooled phase II/III population. TEAEs and discontinuations due to TEAEs in this subgroup were dose related and similar to the pooled phase II/III population. In the remaining subgroup of patients, i.e. those not taking 'traditional' sodium channel-blocking AEDs as part of their concomitant AED regimen (n = 231; 18%), a pronounced, dose-related seizure reduction was observed with lacosamide (p < 0.01, 400 and 600 mg/day for median percent seizure reduction and 50% or 75% responder rates). Also in this group, incidences of TEAEs were low, and discontinuations due to TEAEs did not appear to increase with dose. Analyses of ECG, laboratory and vital signs (including bodyweight) assessments did not identify abnormalities in either subgroup that were outside of the known safety profile of lacosamide observed in the pooled phase II/III population.

CONCLUSION

In this post hoc exploratory analysis, adjunctive lacosamide demonstrated significant seizure reduction over placebo regardless of the inclusion of 'traditional' sodium channel blockers in the concomitant AED regimen. Future prospective studies evaluating single AED combinations (e.g. lacosamide plus one other drug) are needed to better evaluate the potential for additive or synergistic effects of lacosamide in combination with AEDs not considered 'traditional' sodium channel blockers.

The Art of Managing Conversions between Antiepileptic Drugs: Maximizing Patient Tolerability and Quality of Life

Conversion between anti-epilectic drugs (AEDs) is frequently necessary in epilepsy care, exposing patients to a risk of incurring adverse effects and reduced quality of life. Little practical guidance is available to practitioners to guide conversions between AED monotherapies, or in adding a new adjunctive AED into a polytherapy regimen. This article reviews the impact of adverse effects of AEDs on quality of life in epilepsy patients, then reviews several important patient-related factors such as age, gender, medical and psychiatric co-morbidities, and co-medications that must be considered when selecting AEDs and ensuring tolerable and safe AED conversions. Practical strategies for transitional polytherapy AED conversion are then considered in different commonly encountered clinical scenarios in newly diagnosed and refractory epilepsy care, including inadequate seizure control, intolerable adverse effects, or idiosyncratic safety hazards. Successful conversion between AEDs requires regular monitoring for patient-reported adverse effects and appropriately reactive adjustment of AED therapy to maximize patient quality of life.