Rational polytherapy

Rational polytherapy with lacosamide in clinical practice: results of a Spanish cohort analysis RELACOVA

There has been little long-term success with polytherapy for patients with refractory partial-onset epilepsy. The rational combination of antiepileptic drugs based on their mechanism of action may help improve treatment efficacy and tolerability. Lacosamide, a novel sodium channel blocker (SCB), was investigated in 158 patients with partial-onset epilepsy in the prospective, multicenter, observational, RELACOVA cohort study conducted in Spain. After 12 months' treatment with lacosamide, 47% of patients were responders (≥50% reduction in seizure frequency) and 24% were seizure free. Lacosamide was well tolerated; dizziness was the most frequent adverse event. Efficacy was better (responder rate, 65% vs 38%; seizure free rate, 35% vs 17%) and there was a lower adverse event rate (33% vs 58%) in patients receiving non-SCBs (n=49) versus those receiving SCBs (n=104) as concomitant therapy at baseline. Further investigation of lacosamide combination therapy is warranted.

Multifunctional QD-based co-delivery of siRNA and doxorubicin to HeLa cells for reversal of multidrug resistance and real-time tracking

Co-delivery of siRNA and chemotherapeutic agents has been developed to combat multidrug resistance in cancer therapy. Recently, we developed a series of quantum dots (QDs) functionalized by β-cyclodextrin (β-CD) coupled to amino acids, some of which can be used to facilitate the delivery of siRNA. In this study, two CdSe/ZnSe QDs modified with β-CD coupled to L-Arg or L-His were used to simultaneously deliver doxorubicin (Dox) and siRNA targeting the MDR1 gene to reverse the multidrug resistance of HeLa cells. In this co-delivery system, Dox was firstly encapsulated into the hydrophobic cavities of β-CD, resulting in bypass of P-glycoprotein (P-gp)-mediated drug efflux. After complex formation of the mdr1 siRNA with Dox-loaded QDs via electrostatic interaction, significant down-regulation of mdr1 mRNA levels and P-gp expression was achieved as shown by RT-PCR and Western blotting experiments, respectively. The number of apoptotic HeLa cells after treatment with the complexes substantially exceeded the number of apoptotic cells induced by free Dox only. The intrinsic fluorescence of the QDs provided an approach to track the system by laser confocal microscopy. These multifunctional QDs are promising vehicles for the co-delivery of nucleic acids and chemotherapeutics and for real-time tracking of treatment.

No pharmacokinetic interaction between lacosamide and valproic acid in healthy volunteers

Two open-label, randomized, multiple-dose clinical studies evaluated the potential for pharmacokinetic interaction between the antiepileptic drugs lacosamide and valproic acid. The influence of lacosamide on valproic acid pharmacokinetics (trial A) and valproic acid on lacosamide pharmacokinetics (trial B) was investigated in 32 healthy male volunteers, 16 in each trial. Volunteers in trial A received valproic acid (300 mg bid) with randomization to either early or late addition of lacosamide (200 mg bid). Those in trial B received lacosamide (200 mg bid) with randomization to either early or late addition of valproic acid (300 mg bid). Area under the concentration-time curve during a 12-hour dosing interval at steady state (AUC(τ,ss)) and maximum steady-state plasma drug concentration (C(max,ss)) were measured for each drug alone and together and tested for equivalence. The point estimates (90% confidence intervals) for AUC(τ,ss) and C(max,ss) were 104% (99%-109%) and 101% (97%-107%), respectively, for valproic acid and 100% (98%-103%) and 101% (96%-107%), respectively, for lacosamide, which were within the generally accepted equivalence range of 80% to 125%. No changes in the rate or extent of absorption, terminal half-life, or time to maximum concentration were observed. These results suggest that lacosamide and valproic acid have no relevant pharmacokinetic drug-drug interaction.

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.

Pregabalin or placebo used adjunctively with levetiracetam in refractory partial-onset epilepsy: a post hoc efficacy and safety analysis in combined clinical trials

OBJECTIVE

Some patients with epilepsy require treatment with >1 adjunctive antiepileptic drug (AED) to achieve adequate seizure remission. The purpose of this analysis was to evaluate the efficacy and safety of adding adjunctive pregabalin to an AED regimen that included levetiracetam in patients with refractory partial-onset epilepsy.

RESEARCH DESIGN AND METHODS

Data from the pregabalin and placebo arms of two placebo-controlled, double-blind, randomized studies of pregabalin in patients who received adjunctive treatment with levetiracetam in addition to ≥1 other AEDs were pooled for this post hoc analysis. Patients (aged ≥18 years) had ≥4 partial-onset seizures and no 28-day period free of seizures during baseline. Efficacy outcomes included Response Ratio (RRatio), change from baseline in seizure frequency, proportion of patients with ≥50% reduction in seizure frequency, and 28-day seizure-freedom rate. Safety was evaluated using adverse events (AEs).

RESULTS

In total, 138 patients were included in the analysis (placebo, n = 47; pregabalin, n = 91). Pregabalin was significantly better than placebo for difference in least squares mean of the RRatio (-16.4; 95% confidence interval [CI]: -28.5, -4.5; p = 0.0085), median of the difference in percentage change from baseline in seizure frequency (-22.3; 95% CI: -40.1, -7.2; p = 0.0095), and proportion of 50% responders (36.3 vs. 17.0; odds ratio, 3.2; 95% CI: 1.3, 8.3; p = 0.018), but not 28-day seizure-freedom rate (7 [7.7%] vs. 2 [4.3%]; p = 0.353). The most common AEs when adding pregabalin were dizziness/vertigo, fatigue, somnolence, blurred vision, and increased weight that were not proportional to the number of concomitant AEDs.

CONCLUSIONS

In this population of patients with refractory partial-onset seizures, adding pregabalin to an AED regimen with levetiracetam produced further seizure reductions. The safety profile of pregabalin in patients receiving levetiracetam and ≥1 other AEDs did not appear to be compromised by the number of concomitant AEDs.

Lacosamide as adjunctive therapy for partial-onset epileptic seizures: a review of the clinical and economic literature

OBJECTIVE

This article provides a short but comprehensive pharmacotherapeutic update of adjunctive therapy with lacosamide for partial-onset seizures in adult patients.

RESEARCH DESIGN AND METHODS

PubMed, Centre for Reviews and Dissemination databases, Cochrane Database of Systematic Reviews, EconLit were searched from January 1999 to September 2010. Studies evaluating intravenous lacosamide were excluded because this article focuses on chronic adjunctive therapy.

RESULTS

Three randomised, multicentre, double-blind, placebo-controlled trials have investigated the efficacy of lacosamide in 1300 adults with epilepsy. The median percent reduction in seizure frequency per 28 days from baseline to maintenance was 18.4% for placebo, 33.3% for lacosamide 200 mg/day (p < 0.01), 36.8% for 400 mg/day (p < 0.001), 39.4% for 600 mg/day. The percentage of patients attaining a seizure frequency reduction of ≥50% was 22.6% with placebo, 34.1% with lacosamide 200 mg/day (p < 0.05), 39.7% with lacosamide 400 mg/day (p < 0.001), 39.6% with lacosamide 600 mg/day. Three open-label extension studies showed that long-term treatment with lacosamide produced sustained efficacy in and was well-tolerated by patients. Three economic evaluations used a similar design to determine the cost effectiveness of lacosamide from the healthcare payer perspective in Sweden, Finland and Belgium. These studies showed that standard anti-epileptic drug therapy plus lacosamide is likely to constitute a cost-effective alternative. The budget impact of introducing lacosamide is likely to be limited.

CONCLUSIONS

The evidence on lacosamide was limited and studies suffered from a number of methodological limitations. Lacosamide appears to be a safe, efficacious and cost-effective adjunctive therapy for partial-onset epileptic seizures in adult patients. However, these results need to be validated by studies that explore the impact of lacosamide in real-life clinical practice.

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.

Clinical comparability of the new antiepileptic drugs in refractory partial epilepsy: a systematic review and meta-analysis

PURPOSE

Evaluate the clinical comparability of new antiepileptic drugs (AEDs) in partial refractory epilepsy.

METHODS

Systematic review of randomized trials (RCTs) comparing a new AED (add-on treatment) with placebo or another AED.

PRIMARY OUTCOMES

responder (≥50% seizure reduction) and withdrawal (tolerability) rates. Pooled estimates of odds ratios (ORs) and number needed treat/harm (NNT/NNH) taking into account baseline risk were derived by random-effects meta-analysis. Adjusted frequentist indirect comparisons between AEDs were estimated.

KEY FINDINGS

Sixty-two placebo-controlled (12,902 patients) and eight head-to-head RCTs (1,370 patients) were included. Pooled ORs for responder and withdrawal rates (vs. placebo) were 3.00 [95% confidence interval (CI) 2.63-3.41] and 1.48 (1.30-1.68), respectively. Indirect comparisons of responder rate based on relative measurements of treatment effect (ORs) favored topiramate (1.52; 1.06-2.20) in comparison to all other AEDs, whereas gabapentin (0.67; 0.46-0.97) and lacosamide (0.66; 0.48-0.92) were less efficacious, without significant heterogeneity. When analyses were based on absolute estimates (NNTs), topiramate and levetiracetam were more efficacious, whereas gabapentin and tiagabine were less efficacious. Withdrawal rate was higher with oxcarbazepine (OR 1.60; 1.12-2.29) and topiramate (OR 1.68; 1.07-2.63), and lower with gabapentin (OR 0.65; 0.42-1.00) and levetiracetam (OR 0.62; 0.43-0.89).

SIGNIFICANCE

The differences found are of relatively small magnitude to allow a definitive conclusion about which new AED(s) has superior effectiveness. This uncertainty probably reflects the limitations of conclusions based on indirect evidence. The process of pharmacologic clinical decision making in partial refractory epilepsy probably depends more on other aspects, such as individual patient characteristics and pharmacoeconomics, than on available controlled randomized evidence.

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.

Status epilepticus treatment and outcome in children: what might the future hold?

Status epilepticus is a life-threatening emergency that requires urgent treatment. Over the past decade, numerous advances have been made in the management of status epilepticus. Clinical studies have now established the benefit of early, aggressive treatment of status epilepticus with benzodiazepines in both prehospital and hospital settings. Neuroscientific advances are revealing mechanisms of status epilepticus that could translate into targets for treating acute status epilepticus and even reducing epileptogenesis. This article discusses future trends in the diagnosis, neurobiology, and treatment of status epilepticus.

Rational Polytherapy with Antiepileptic Drugs

Approximately 30-40% of patients do not achieve seizure control with a single antiepileptic drug (AED). With the advent of multiple AEDs in the past 15 years, rational polytherapy, the goal of finding combinations of AEDs that have favorable characteristics, has become of greater importance. We review the theoretical considerations based on AED mechanism of action, animal models, human studies in this field, and the challenges in finding such optimal combinations. Several case scenarios are presented, illustrating examples of rational polytherapy.

Mechanisms of action of antiepileptic drugs: the search for synergy

PURPOSE OF REVIEW

The aim is to review rational polytherapy of antiepileptic drugs in terms of conventional and novel mechanisms of action, consider combinations that might be beneficial when used as polytherapy, and discuss whether animal models can predict clinical efficacy.

RECENT FINDINGS

Many patients with epilepsy require concurrent treatment with more than one antiepileptic drug (rational polytherapy), but there is little information available as to which drugs might work best in combination. Conventional antiepileptic drugs act by blocking sodium channels or enhancing gamma-aminobutyric acid function. Some newer antiepileptic drugs have novel mechanisms of action, including impairment of the slow inactivation of sodium channels, binding to the presynaptic vesicle protein SV2A, binding to the calcium channel alpha2delta subunit, and opening select potassium channels. Several antiepileptic drugs have multiple or uncertain mechanisms of action. Quantitative techniques such as isobolography can be used to compare the efficacy and side effects of antiepileptic drug combinations in animals. However, neither such methods nor antiepileptic drug mechanisms of action have yet proven useful in predicting clinical benefit in patients.

SUMMARY

Animal models can be used to help predict drug combinations that might be effective clinically, based on novel mechanisms of action. However, at this point, antiepileptic drug choice in patients with epilepsy remains empirical.

Management of epilepsy in drug-resistant patients

Epilepsy affects > 2 million people in the United States, making it one of the most common neurobiological conditions. Typically, epilepsy is treated with one of several available antiepileptic drugs and patients are able to experience freedom from seizures with minimal side effects. However, there are some patients who do not respond to treatment and require the use of multiple drug combinations or surgical intervention. Although there are few studies supporting its use, multi-drug regimens have been known to be helpful for patients, although clinicians should monitor patients for adverse side effects. Vagus nerve stimulation is the only US Food and Drug Administration-approved surgical neurostimulation therapy for epilepsy, and patients' conditions often progress for many years before epilepsy surgery options are considered. Lastly, due to the chronic nature of epilepsy, clinicians should be aware of the presence of comorbid psychiatric conditions as well. This supplement is Part One in the "Case in Point: Evidence-Based Insights for Epilepsy Management" series. In this Expert Review Supplement, Andrew J. Cole, MD, FRCPC, outlines a case of a patient with drug resistant epilepsy, and Brien J. Smith, MD, outlines the best practices for the case patient including discussion on defining drug resistance in patients as well as the benefits and risks of available and emerging drug and surgical treatments.