Extended-release formulations for the treatment of epilepsy

Predictors of valproic acid steady-state serum levels in adult and pediatric psychiatric inpatients: a comparative analysis

RATIONALE

Valproic acid (VPA) is commonly used as a second-line mood stabilizer or augmentative agent in severe mental illnesses. However, population pharmacokinetic studies specific to psychiatric populations are limited, and clinical predictors for the precision application of VPA remain undefined.

OBJECTIVES

To identify steady-state serum VPA level predictors in pediatric/adolescent and adult psychiatric inpatients.

METHODS

We analyzed data from 634 patients and 1,068 steady-state therapeutic drug monitoring (TDM) data points recorded from 2015 to 2021. Steady-state VPA levels were obtained after tapering during each hospitalization episode. Electronic patient records were screened for routine clinical parameters and co-medication. Generalized additive mixed models were employed to identify independent predictors.

RESULTS

Most TDM episodes involved patients with psychotic disorders, including schizophrenia (29.2%) and schizoaffective disorder (17.3%). Polypharmacy was common, with the most frequent combinations being VPA + quetiapine and VPA + promethazine. Age was significantly associated with VPA levels, with pediatric/adolescent patients (< 18 years) demonstrating higher dose-adjusted serum levels of VPA (β = 7.6±2.34, p < 0.001) after accounting for BMI. Women tended to have higher adjusted VPA serum levels than men (β = 5.08±1.62, p < 0.001). The formulation of VPA (Immediate-release vs. extended-release) showed no association with VPA levels. Co-administration of diazepam exhibited a dose-dependent decrease in VPA levels (F = 15.7, p < 0.001), suggesting a potential pharmacokinetic interaction.

CONCLUSIONS

This study highlights the utility of population-specific pharmacokinetic data for VPA in psychiatric populations. Age, gender, and co-administration of diazepam were identified as predictors of VPA levels. Further research is warranted to establish additional predictors and optimize the precision application of VPA in psychiatric patients.

Efficacy, Safety, and Retention Rate of Extended-Release Divalproex Versus Conventional Delayed-Release Divalproex: A Meta-Analysis of Controlled Clinical Trials

Purpose: A novel once-daily divalproex-extended release (ER) dose formulation has been developed; this formulation prolongs the therapeutic serum levels of the drug, compared with the twice-daily conventional divalproex-delayed release (DR) formulation. This study aimed to systematically examine and compare the efficacy, safety, and retention rates of the ER divalproex (VPA-ER) and conventional DR divalproex (VPA-DR) formulations.

Methods: Randomized control trials (RCTs) reporting the efficacy, adverse events (AEs), and medication compliance of ER and DR divalproex were searched in online databases, including PubMed, Embase, and Cochrane Library databases, by searching MeSH words and term words. Observational studies with potential biases were excluded. The meta-analysis was performed using Stata 16.0 software.

Findings: Thirteen RCTs, involving 1,028 participants, were included in this meta-analysis. Efficacy, AEs, and drug retention rates were the main study outcomes. According to our study, VPA-ER presented clinically significant benefits compared with the placebo in the population with bipolar disorder (BD) (39.5% versus 27.2%, p < 0.001). A similar efficacy of VPA-ER and VPA-DR in controlling seizures was observed in epilepsy patients (87.4% versus 86.5%, p = 0.769). A significantly lower incidence of AEs was reported in the VPA-ER group than in the placebo group (26.8% versus 34.8%, p = 0.003). By contrast, there was no evidence of difference in safety between VPA-ER and VPA-DR (29.4% versus 30.5%, p = 0.750). In addition, the drug retention rate was significantly lower in the VPA-ER group than in the placebo group (76.0% versus 82.7%, p = 0.020), especially in migraine patients (p = 0.022) and in patients who were treated for fewer than 4 weeks (p = 0.018).

Implications: The efficacy of VPA-ER was significantly superior to that of the placebo treatment, which provided efficacy similar to that of conventional VPA-DR. VPA-ER is well tolerated with a low rate of AEs compared to the placebo. In addition, the acceptable medicine compliance of VPA-ER was conducive to the long-term maintenance treatment of chronic diseases. Although we analyzed open labels and crossover design RCTs, large-scale multicenter studies on the efficacy and medicine compliance of new ER formulations with less AEs are required to validate our conclusion.

Efficacy and Safety of Tramadol Hydrochloride Twice-Daily Sustained-Release Bilayer Tablets with an Immediate-Release Component for Chronic Pain Associated with Knee Osteoarthritis: A Randomized, Double-Blind, Placebo-Controlled, Treatment-Withdrawal Study

Background and Objectives

Knee osteoarthritis pain is a chronic form of pain for which conventional non-steroidal anti-inflammatory drugs may provide insufficient analgesia. Twice-daily tramadol hydrochloride (65% sustained-release/35% immediate-release) bilayer tablets are a novel formulation of tramadol developed for managing chronic pain. The objectives of this study were to examine the effectiveness and safety of this formulation in patients with chronic knee osteoarthritis pain.

Methods

This was a multicenter, randomized, placebo-controlled, double-blind, parallel-group, treatment-withdrawal study. Patients with a reduction in Numeric Rating Scale (NRS) for pain of ≥2 points during a 1–3-week, open-label, tramadol dose-escalation period (100–300 mg/day) were randomized to continue tramadol or switched to placebo for 4 weeks (double-blind period). Patients with inadequate efficacy (increase in NRS ≥2 points/patient request) were withdrawn. Outcomes included the time to inadequate analgesic efficacy from randomization (primary endpoint), the cumulative retention rate, and safety.

Results

Overall, 249 and 160 patients entered the dose-escalation and double-blind periods, respectively (tramadol 79; placebo 81). Kaplan–Meier analysis revealed superiority of tramadol (log-rank p = 0.042), and a hazard ratio of 0.50 (95% confidence interval [CI] 0.25–0.99). Documentation of an inadequate analgesic effect was less frequent in the tramadol group (15.4%, 95% CI 8.2–25.3% vs. 30.9%, 95% CI 21.1–42.1%). The cumulative retention rate was greater in the tramadol group (83.7% vs. 69.0%). Adverse events occurred in 80.6% (200/248) of patients in the open-label period, and in 38.5% (30/78) and 13.6% (11/81) of patients in the tramadol and placebo groups, respectively, in the double-blind period. Opioid-associated adverse events, such as nausea, vomiting, constipation, somnolence, and dizziness, were the most frequent events.

Conclusion

This study demonstrated the analgesic efficacy and safety of sustained-release tramadol tablets with an immediate-release component for chronic knee osteoarthritis pain.

Trial registration

JapicCTI-132103 (Japan Pharmaceutical Information Center; registration date February 25, 2015)

Supplementary Information

The online version contains supplementary material available at 10.1007/s40261-022-01139-5.

Designing Drug Regimens that Mitigate Nonadherence

Medication adherence is a well-known problem for pharmaceutical treatment of chronic diseases. Understanding how nonadherence affects treatment efficacy is made difficult by the ethics of clinical trials that force patients to skip doses of the medication being tested, the unpredictable timing of missed doses by actual patients, and the many competing variables that can either mitigate or magnify the deleterious effects of nonadherence, such as pharmacokinetic absorption and elimination rates, dosing intervals, dose sizes, and adherence rates. In this paper, we formulate and analyze a mathematical model of the drug concentration in an imperfectly adherent patient. Our model takes the form of the standard single compartment pharmacokinetic model with first-order absorption and elimination, except that the patient takes medication only at a given proportion of the prescribed dosing times. Doses are missed randomly, and we use stochastic analysis to study the resulting random drug level in the body. We then use our mathematical results to propose principles for designing drug regimens that are robust to nonadherence. In particular, we quantify the resilience of extended release drugs to nonadherence, which is quite significant in some circumstances, and we show the benefit of taking a double dose following a missed dose if the drug absorption or elimination rate is slow compared to the dosing interval. We further use our results to compare some antiepileptic and antipsychotic drug regimens.

Efficacy, safety, and retention rate of extended-release divalproex versus conventional delayed-release divalproex: A protocol for systematic review and meta-analysis

BACKGROUND

A novel once-daily divalproex-extended release (VPA-ER) dose formulation has been developed, which prolongs therapeutic serum levels compared with that of twice-daily conventional divalproex-delayed release (VPA-DR). Currently, there is lack of meta-analysis focusing on drug retention rate between VPA-ER and VPA-DR. Thus, our study is the first one that aims to systematically examine and compare the efficacy, safety, and retention rate of VPA-ER and VPA-DR.

METHODS

Online databases including MEDLINE via PubMed, Cochrane Library, Embase (up to October 30, 2021) will be applied for literature screen. We will conduct meta-analysis by using Stata16.0 software.

RESULTS

This study aims to evaluate the efficacy, safety, and drug retention rate of VPA-ER versus conventional VPA-DR.

CONCLUSION

Once-daily VPA-ER may present a positive efficacy and not increase the incidence of AEs and has a higher retention rate for patients, which can be used as a substitute for conventional VPA-DR.INPLASY registration number: INPLASY2021110090(DOI: 10.37766/inplasy2021.11.0090).

Owner compliance in canine epilepsy

BACKGROUND

Poor medication compliance by human epilepsy patients is one of the leading causes of treatment failure and increased seizure frequency. The aim of this cross-sectional study was to analyse owner compliance in pharmacological treatment of canine idiopathic epilepsy and to identify factors associated with poor compliance.

METHODS

The number of antiseizure drug tablets was recorded to determine if the patient received sufficient tablets to cover the time period between prescriptions and to assess compliant prescription cycles. Additionally, compliance was assessed by an online survey of owners.

RESULTS

For the prescription monitoring data from 94 cases from three small animal practices in the United Kingdom revealed an overall median compliance of 56%. Thirt-three per cent of owners were >80% compliant, while 21% were 100% compliant. During a non-compliant prescription cycle, a patient missed a median of 6 days (0.11-519 days) of treatment. Patients on polytherapy had higher compliance rates than on monotherapy (p = 0.031). The survey (229 respondents from online canine epilepsy groups) showed that low daily dosing was associated with better compliance (p = 0.049).

CONCLUSION

Owner compliance was subpar in this study and could represent a significant issue in epilepsy management, which needs to be considered by veterinary surgeons when treating canine epilepsy.

Use of extended-release and immediate-release anti-seizure medications with a long half-life to improve adherence in epilepsy: A guide for clinicians

Poor adherence to anti-seizure medications (ASMs) is associated with breakthrough seizures and potentially increased toxicity in patients with epilepsy. Extended-release (ER) drugs and immediate-release (IR) drugs with a long half-life (t_1/2) that permit once-daily dosing (such as, perampanel, zonisamide, lamotrigine [IR, ER] and topiramate [ER]) have a number of advantages over short t_1/2 ASMs that require multiple daily dosing. These advantages include simplification of dosing regimens, reduction in pill burden, and a decrease in the peak-to-trough fluctuations in serum drug concentration that may be associated with a decreased risk of adverse effects and seizures. Such properties have wider implications in improving patient adherence to treatment. This article is intended as a practical guide for clinicians that provides an overview of the features of ER ASMs and long t_1/2 IR ASMs that are advantageous in the context of patient adherence and pharmacokinetic "forgiveness" (after missing a dose). In addition, we note that efforts to improve adherence should not depend solely on drug dosing regimens and drug pharmacokinetics, but should be part of a wider strategy that includes therapeutic drug monitoring, improved healthcare provider-patient dialogue, patient education, and the use of "reminder" technology.

Efficacy and safety of perampanel in generalized and focal to bilateral tonic-clonic seizures: A comparative study of Asian and non-Asian populations

Perampanel is an approved adjunctive treatment for focal seizures with or without focal to bilateral tonic-clonic (FBTC) seizures and generalized tonic-clonic (GTC) seizures. We compared efficacy and safety of perampanel vs placebo in Asian and non-Asian populations in a post hoc analysis of pooled data from 5 randomized phase 3 studies. Patients (≥12 years old) with focal + FBTC seizures received perampanel 2, 4, 8, or 12 mg or placebo; patients with GTC seizures received perampanel 8 mg or placebo (titration: 4-6 weeks; maintenance: 13 weeks). Efficacy endpoints included median percentage change in FBTC or GTC seizure frequency per 28 days and 50% responder rate relative to baseline. Median percentage change in FBTC seizure frequency was significantly greater for perampanel 8 and 12 mg than placebo in the Asian population (median difference from placebo: -30.32%, P = 0.0017; -30.06%, P = 0.0008, respectively) and perampanel 4, 8, and 12 mg in the non-Asian population (-35.07%, P = 0.0001; -37.78%, P < 0.0001; -34.53%, P < 0.0001, respectively). In both populations, median percentage change in GTC seizure frequency was significantly greater for perampanel 8 mg than placebo (median difference from placebo: Asian, -37.37%, P = 0.0139; non-Asian, -27.04%, P = 0.0006). The 50% responder rates were significantly greater than placebo for perampanel 8 and 12 mg for FBTC seizures (Asian: 58.0%, P = 0.0017 and 58.6%, P = 0.0013, respectively; non-Asian: 59.3%, P < 0.0001 and 54.3%, P = 0.0050, respectively) and perampanel 8 mg for GTC seizures (Asian: 57.6%, P = 0.0209; non-Asian: 68.8%, P = 0.0329). Pooled FBTC/GTC seizure data showed generally similar patterns of response to perampanel in both populations. The most frequent treatment-related adverse events were fatigue, irritability, dizziness, somnolence, and headache. Perampanel was effective, well tolerated, and can be considered a therapeutic option for FBTC/GTC seizures in Asian populations.

Changing the Drug Delivery System: Does It Add to Non-Compliance Ramifications Control? A Simulation Study on the Pharmacokinetics and Pharmacodynamics of Atypical Antipsychotic Drug

This study investigates the pharmacokinetic (PK) and pharmacodynamic (PD) consequences of shifting from Quetiapine fumarate immediate-release (IR) to extended-release (XR) formulation in non-adherent schizophrenia patients. Monte-Carlo simulations using population PK and PD models were implemented to predict the time course of plasma concentration and Brief Psychiatric Rating Scale (BPRS) scores following the oral administration of 200 mg Seroquel^® every 12 h and 400 mg Seroquel XR^® every 24 h in patients experiencing dose delay, omission or doubling. Parameters were computed and their distributions were compared using the Kolmogorov–Smirnov test. Dose irregularities with both formulations had different effects on plasma concentration and %reduction in BPRS scores from baseline. However, the odds ratio of getting a %reduction in BPRS below 14%, or plasma concentration exceeding 500 µg/L, were comparable for adherent and non-adherent patients. Plasma therapeutic concentration after treatment cessation was maintained for <24 h in 48% and 29.6% of patients, and a steady state recovery time of <48 h was achieved in 51% and 13.4% of patients on the IR and XR formulations, respectively. Monte-Carlo simulations predict that the risks associated with the IR dose irregularities are not worsened when the XR formulation is used instead. Non-adherence events involving a single dose of either formulation do not require rescue doses.

Formulation of Extended-Release Beads of Lamotrigine Based on Alginate and <i>Cassia fistula</i> Seed Gum by QbD Approach

AIM

This study was focused on the formulation of the multi-unit extended-release peroral delivery device of lamotrigine for better management of epilepsy.

BACKGROUND

The single-unit extended-release peroral preparations often suffer from all-or-none effect. A significant number of multi-unit delivery systems have been reported as a solution to this problem. But most of them are found to be composed of synthetic, semi-synthetic or their combination having physiological toxicity as well as negative environmental impact. Therefore, fabrication and formulation of multi-unit extended-release peroral preparations with natural, non-toxic, biodegradable polymers employing green manufacturing processes are being appreciated worldwide.

OBJECTIVE

Lamotrigine-loaded extended-release multi-unit beads have been fabricated with the incorporation of a natural polysaccharide Cassia fistula seed gum in calcium-cross-linked alginate matrix employing a simple green process and 23 full factorial design.

METHODS

The total polymer concentration, polymer ratio and [CaCl2] were considered as independent formulation variables with two different levels of each for the experiment-design. The extended-release beads were then prepared by the ionotropic gelation method using calcium chloride as the crosslinkerions provider. The beads were then evaluated for drug encapsulation efficiency and drug release. ANOVA of all the dependent variables such as DEE, cumulative % drug release at 2h, 5h, 12h, rate constant and dissolution similarity factor (f2) was done by 23 full factorial design using Design-Expert software along with numerical optimization of the independent variables in order to meet USP-reference release profile.

RESULTS

The optimized batch showed excellent outcomes with DEE of 84.7 ± 2.7 (%), CPR2h of 8.41± 2.96 (%), CPR5h of 36.8± 4.7 (%), CPR12h of 87.3 ± 3.64 (%) and f2 of 65.9.

CONCLUSION

This approach of the development of multi-unit oral devices utilizing natural polysaccharides might be inspiring towards the world-wide effort for green manufacturing of sustained-release drug products by the QbD route.

A Clinician's Guide to Oral Extended-Release Drug Delivery Systems in Epilepsy

Epilepsy is one of the most common chronic neurologic disorders that affects individuals of all ages. It is primarily managed with antiepileptic drugs (AEDs), with the goal of maintaining complete seizure control combined with minimal or no adverse effects. Oral administration is the mainstay of AED delivery for patients with chronic epilepsy and consists essentially of immediate-release (IR) and modified-release (delayed-release and extended-release [ER]) dosage formulations. Extended-release formulations (hydrophilic or hydrophobic matrix systems, reservoir systems, and osmotic-release systems) release a drug in a controlled manner during an extended period of time following administration. Extended-release formulations have many advantages compared with IR formulations, including simplification of dosing regimens, reduction in pill burden, and reduction in the peak-to-trough fluctuations in serum drug concentration that may be associated with a decreased risk of adverse effects and of seizures. These advantages have the potential to increase adherence to antiepileptic therapy, improve the quality of life of patients, and reduce health care costs. This article, which is intended as a practical guide for clinicians, reviews the properties of the different ER AED formulations currently available and discusses the advantages of ER over IR formulations. Subsequently, an explanation of the technologic basis of the different oral ER formulations, the critical attributes that differentiate ER products, and their individual strengths and weaknesses is provided. Specific recommendations to practitioners on treating patients with ER formulations are included.

Regularity of self-reported daily dosage of mood stabilizers and antipsychotics in patients with bipolar disorder

BACKGROUND

Polypharmacy is often prescribed for bipolar disorder, yet medication non-adherence remains a serious problem. This study investigated the regularity in the daily dosage taken of mood stabilizers and second generation antipsychotics.

METHODS

Daily self-reported data on medications taken and mood were available from 241 patients with a diagnosis of bipolar disorder who received treatment as usual. Patients who took the same mood stabilizer or second generation antipsychotic for ≥ 100 days were included. Approximate entropy was used to determine serial regularity in daily dosage taken. Generalized estimating equations were used to estimate if demographic or clinical variables were associated with regularity.

RESULTS

There were 422 analysis periods available from the 241 patients. Patients took drugs on 84.4% of days. Considerable irregularity was found, mostly due to single-day omissions and dosage changes. Drug holidays (missing 3 or more consecutive days) were found in 35.8% of the analysis periods. Irregularity was associated with an increasing total number of psychotropic drugs taken (p = 0.009), the pill burden (p = 0.026), and the percent of days depressed (p = 0.049).

CONCLUSION

Despite low missing percent of days, daily drug dosage may be irregular primarily due to single day omissions and dosage changes. Drug holidays are common. Physicians should expect to see partial adherence in clinical practice, especially with complex drug regimens. Daily dosage irregularity may impact the continuity of drug action, contribute to individual variation in treatment response, and needs further study.

Development of Extended-Release Oral Flexible Tablet (ER-OFT) Formulation for Pediatric and Geriatric Compliance: an Age-Appropriate Formulation

Development of age-appropriate formulation suitable for pediatric and geriatric patients involves various challenges. The objective of this research was to develop extended-release oral flexible tablet (ER-OFT) formulation using carbamazepine (CBZ) as model drug for pediatric and geriatric compliance. ER-microparticles of carbamazepine, a BCS class 2, and narrow therapeutic index (NTI) drug, were prepared using ethyl cellulose as matrixing polymer and hypromellose as hydrophilic pore former. Microparticles were prepared using high-shear granulator fitted with an atomizing spray system. Granulation of carbamazepine and ethyl cellulose (EC-FP) with ethanolic binder solution resulted in ER-microparticles with extended-release >16 h. Release kinetics of ER microparticles showed Higuchi model by drug diffusion and erosion. Korsemeyer-peppas release exponent "n" value 0.42 suggested Fickian diffusion. ER-OFT was prepared by blending of ER-microparticles with water-insoluble compressible aid and disintegrating agent. ER-OFT was characterized for performance characteristics and elemental impurities. As the polymer content in formulation was <10%, the size of ER-OFT was smaller compared to marketed ER-formulations. ER-OFT showed in vitro disintegration time of <30 s as per USP and dispersion time of ∼60 to 180 s in 5 to 10 mL of water. Drug release profiles of ER-microparticles and ER-OFT were comparable as f2 values were >50. In vitro dissolution of ER-OFT was comparable to the marketed ER formulation in the pH range of GIT. ER-OFT can be orally swallowed, orally disintegrating, and used as dispersible tablets. Compared to non-disintegrating type ER-formulations, ER-OFT would provide uniform drug release in GIT with low within-subject variability an essential criterion for NTI drug.

Topiramate Extended Release: A Review in Epilepsy

Once-daily oral topiramate extended release (USL255; hereafter referred to as topiramate XR) [QUDEXY(®) XR] is approved in the USA for use as initial monotherapy and adjunctive therapy in patients aged ≥2 years with partial-onset seizures (POS) or primary generalized tonic-clonic seizures and as adjunctive therapy in patients aged ≥2 years with seizures associated with Lennox-Gastaut syndrome. Compared with twice-daily topiramate immediate release at the same total daily dose, topiramate XR provided bioequivalent exposure, an extended absorption rate (permitting convenient once-daily dosing) and more constant therapeutic plasma concentrations (potentially minimizing topiramate-associated adverse events). Switching between the two formulations did not affect the maintenance of topiramate concentrations. Moreover, the contents of a topiramate XR capsule may be sprinkled on to soft food for patients who have difficulty swallowing. In a multinational phase III study in adults with refractory POS, adjunctive topiramate XR was associated with significantly greater improvements from baseline in weekly median seizure frequency and the proportion of patients achieving a ≥50 % reduction in seizure frequency compared with placebo. These benefits were sustained during a 55-week open-label extension study. Adjunctive topiramate XR was generally well tolerated in these studies, with the majority of treatment-emergent adverse events being mild or moderate in intensity. In conclusion, current evidence suggests once-daily topiramate XR extends the treatment options currently available for patients aged ≥2 years with epilepsy, with its dosing regimen potentially delivering tolerability and adherence advantages over AEDs that require more frequent administration.

Response Surface Analysis and Nonlinear Optimization Algorithm for Maximization of Clinical Drug Performance: Application to Extended-Release and Long-Acting Injectable Paliperidone

Model-based approach is recognized as a tool to make drug development more productive and to better support regulatory and therapeutic decisions. The objective of this study was to develop a novel model-based methodology based on the response surface analysis and a nonlinear optimizer algorithm to maximize the clinical performances of drug treatments. The treatment response was described using a drug-disease model accounting for multiple components such as the dosage regimen, the pharmacokinetic characteristics of a drug (including the mechanism and the rate of drug delivery), and the exposure-response relationship. Then, the clinical benefit of a treatment was defined as a function of the diseases and the clinical endpoints and was estimated as a function of the target pharmacodynamic endpoints used to evaluate the treatment effect. A case study is presented to illustrate how the treatment performances of paliperidone extended release (ER) and paliperidone long-acting injectable (LAI) can be improved. A convolution-based approach was used to characterize the pharmacokinetics of ER and LAI paliperidone. The drug delivery properties and the dosage regimen maximizing the clinical benefit (defined as the target level of D2 receptor occupancy) were estimated using a nonlinear optimizer. The results of the analysis indicated that a substantial improvement in clinical benefit (from 15% to 27% for the optimization of the in vivo release and from ∼30% to ∼70% for the optimization of dosage regimen) was obtained when optimal strategies were deployed either for optimizing the in vivo drug delivery properties of ER formulations or for optimizing the dosage regimen of LAI formulations.

Ghost-Pill-Buster: A Case Study of Intact Levetiracetam Extended-Release Tablets after Dissolution Testing

BACKGROUND

Orally administered medications in extended-release (ER) dosage forms continue to play a pivotal role in the treatment of various central nervous system disorders. For certain ER dosage forms, pharmaceutical scientists have been familiar with the passage of intact tablet-like objects in patients' feces after administration of ER tablets or capsules based on water-insoluble or slowly dissolving excipients. Nevertheless, because of lack of awareness of the "ghost pill" phenomenon, anxiety has ensued among some patients and clinicians, who have less understanding of how drugs are released from these tablets once ingested. It has been brought to the attention of the US Food and Drug Administration (FDA) that epilepsy patients administered with Teva's levetiracetam ER tablets have noticed intact tablets in their stools and been concerned that they were not getting the needed dose of the drug. In response to neurologists' clinical reporting, the FDA has conducted investigations to confirm a minimal risk of incomplete drug release of Teva's drug product.

OBJECTIVE

The objective of this study was to evaluate the risks of incomplete drug release associated with the passing of intact levetiracetam ER tablets, by conducting in vitro dissolution testing.

METHODS

Dissolution testing of Teva's drug product was performed in accordance with the US Pharmacopeia monograph for levetiracetam ER tablets in phosphate buffer and bio-relevant buffers at different pH values. In addition, dissolution testing was conducted with split and crushed tablets. At the end of the dissolution testing, all samples were visually inspected for any undissolved pieces.

RESULTS

Approximately 90 % of levetiracetam had been released in all dissolution media after 8 h of dissolution. The levetiracetam ER tablets after dissolution testing remained fully intact in all dissolution media. The rates of drug release were significantly faster from split and crushed tablets than that from whole tablets.

CONCLUSION

On the basis of these findings, Teva's levetiracetam ER tablets may appear intact in the stools but have released the drug successfully. The FDA has requested Teva to revise its product labeling to include remarks regarding the potential passing of intact tablets. Since patients who notice ghost pills in their stools may impetuously crush or split the tablets of subsequent doses on their own, healthcare providers should instruct patients to swallow whole tablets throughout the treatment, in accordance with the drug label.

Use of computer simulations to test the concept of dose forgiveness in the era of extended-release (XR) drugs

"Forgiveness" - the difference between a drug's postdose duration of action and its prescribed dosing interval - estimates the margin of therapeutic effect following a missed dose. Because this margin presumably decreases as dosing becomes less frequent, QD dosing of an antiepileptic drug (AED) is expected to be less forgiving than more frequent (e.g., BID) dosing of that same AED. However, if the AED is reformulated as an extended-release (XR) preparation, drug input may be prolonged relative to its immediate-release (IR) counterpart. It therefore stands to reason that forgiveness could be increased by an XR AED that extends the period during which therapeutic plasma concentrations are maintained if a dose is missed. Computer simulation was used to estimate forgiveness for an IR formulation of a hypothetical AED and its XR counterparts reformulated for less frequent dosing. Simulations determined forgiveness when the hypothetical IR AED was dosed TID, BID, and QD and when suitably designed XR formulations were dosed BID and QD. Simulations showed that forgiveness for an XR formulation can equal or exceed that for an IR formulation dosed more frequently.

Pharmacokinetic simulations of topiramate plasma concentrations following dosing irregularities with extended-release vs. immediate-release formulations

BACKGROUND

Once-daily extended-release (XR) antiepileptic drugs (AEDs) offer potential adherence and tolerability advantages over their BID immediate-release (IR) counterparts. However, patients with epilepsy will inevitably be at least occasionally nonadherent with a prescribed dosing regimen, regardless of formulation. Although perturbations in plasma concentrations due to dosing irregularities may have clinical consequences for AEDs with concentration-response relationships, clinical studies that deliberately expose patients to specific dosing irregularities in order to assess the effect on plasma concentrations and determine appropriate corrective actions would be unethical.

METHODS

Computer simulation was used to assess the impact of irregular dosing on topiramate (TPM) concentrations in noninduced (monotherapy/neutral cotherapy) and induced (adjunctive therapy with enzyme-inducing AEDs) states using a population pharmacokinetic (PK) model developed to predict steady-state plasma concentration-time profiles produced by once-daily Trokendi XR (extended-release topiramate capsules, Supernus Pharmaceuticals) and BID TPM-IR.

RESULTS

Computer simulations predicted that, relative to adherent dosing, delaying a dose 4 to 24h in noninduced patients would decrease trough (Cmin) levels 9% to 31% in the case of TPM-IR and 6% to 27% with Trokendi XR; a single omitted dose would reduce Cmin by 21% (TPM-IR) and 27% (Trokendi XR). After dose recovery to correct for a delayed or omitted dose, simulated peak concentration (Cmax) was higher than steady-state Cmax, regardless of formulation, although the magnitude of "overshoot" was consistently lower with Trokendi XR vs. TPM-IR. Doubling of a dose would increase Cmax by 26% and 28%, respectively. Predicted changes for nonadherent vs. adherent dosing were greater in the induced vs. noninduced state but were generally comparable for the two TPM formulations. Because the long half-life of TPM has been cited as a justification for QD dosing of TPM-IR, simulations also compared steady-state PK profiles of once-daily Trokendi XR and QD TPM-IR. Predicted TPM plasma concentration-time profiles were markedly different, as demonstrated by peak-trough fluctuation (QD TPM-IR, 64%; QD Trokendi XR, 18%) and 34% lower Cmin with QD TPM-IR.

CONCLUSIONS

Based on these simulations, dosing irregularities with once-daily Trokendi XR should pose no greater risk than with BID TPM-IR. In the event of a delayed or omitted Trokendi XR dose, TPM concentrations can be restored in noninduced and induced states by administering the delayed/omitted dose at any time during the next dosing interval or by adding the missed dose to the next scheduled dose.

Modified-Release Formulations of Second-Generation Antiepileptic Drugs: Pharmacokinetic and Clinical Aspects

Modified-release or extended-release (XR) formulations are used to decrease the frequency of dosing for drugs with rapid elimination, to improve convenience and adherence. Use of a modified-release formulation can decrease the peak to trough fluctuations in serum concentrations and theoretically improve the therapeutic benefit of the drug, by decreasing adverse events associated with the higher peak concentrations. Once-daily formulations of lamotrigine (Lamictal XR(®)), levetiracetam (Keppra XR(®)), oxcarbazepine (Oxtellar XR(®), Apydan(®) extent) and topiramate (Qudexy XR™, Trokendi XR™) are approved for the treatment of focal and/or generalized onset seizures. Other seizure medications have been approved for non-epileptic symptoms. Gabapentin XR (Gralise(®)) is approved for the treatment of post-herpetic neuralgias. Gabapentin enacarbil XR (Horizant(®)) is a prodrug of gabapentin and is indicated for treatment of post-herpetic neuralgia and restless leg syndrome, a novel indication. For all but Qudexy XR™, the tablets/capsules must be swallowed whole, without cutting, crushing or chewing, in order to maintain the XR properties of the formulation. Qudexy XR™ can be swallowed intact or the capsules can be opened and sprinkled onto soft food for those with swallowing difficulties, for example, children and the elderly. The bioavailability of Gralise(®) and Horizant(®) is significantly affected by food, specifically fat content, and should be taken with a meal to maximize absorption. Overall, the primary advantage of the newly released XR formulations is the once-daily dosing to improve convenience and adherence, with very limited data suggesting improved tolerability.

USL255 extended-release topiramate for the treatment of epilepsy

USL255 is a once-daily, extended-release formulation of the well-established antiepileptic drug topiramate that was recently approved by the US FDA. As a capsule formulation, USL255 can be swallowed intact or opened and sprinkled onto soft food for patients with swallowing difficulties, including children (≥2 years old) and older patients. USL255 has been evaluated in seven key Phase I and III studies. Compared with immediate-release topiramate taken twice daily, once-daily USL255 provides equivalent topiramate exposure with a 26% reduction in plasma fluctuations. A multinational, Phase III, randomized, double-blind, placebo-controlled clinical trial in patients with refractory partial-onset seizures (PREVAIL) demonstrated that USL255 (200 mg/day) significantly improved seizure control and clinical outcomes versus placebo. USL255 is generally safe and well-tolerated, with a low incidence of neuropsychiatric and neurocognitive adverse events. These data suggest that USL255 may provide a useful treatment option for seizure control with convenient once-daily dosing.

Conversion from immediate-release to extended-release lamotrigine improves seizure control

BACKGROUND

Immediate release lamotrigine (LTG-IR) dosing can be limited by peak toxicity. It is thought that peak levels are responsible for some adverse effects such as dizziness, blurred vision, double vision and unsteadiness. At the same time, trough levels may be associated with reduced seizure threshold. The use of extended release lamotrigine (LTG-XR) to replace LTG-IR will be associated with less fluctuation in drug levels-lower peak levels may reduce adverse effects and higher trough levels may improve seizure control. This hypothesis was tested by analyzing seizure control and adverse effects before and after conversion from LTG-IR to LTG-XR in patients who underwent such conversion in 2009-2011.

METHODS

We searched our patient database to identify patients converted from LTG-IR to LTG-XR for persistent seizures or adverse effects from August 2009 until December 31, 2011. We included only patients who took LTG-IR and LTG-XR for at least 6 months each. We excluded patients with nonepileptic seizures, progressive cause of epilepsy, or not keeping a seizure record. We collected the following parameters: age at conversion, LTG-IR dose and dosing schedule, duration on that dose, LTG-XR dose and dosing schedule, LTG serum level before and after conversion, duration of LTG-XR treatment, seizure frequency before and after conversion, and change in adverse experience profile. We also recorded baseline AEDs and any AED change during the course of the analysis.

RESULTS

Fifty five patients (26 female) satisfied the inclusion/exclusion criteria. Their mean age was 45 years (range 23 to 86). Ten were on LTG-IR monotherapy, 24 took LTG-IR plus one other AED, most commonly levetiracetam, and the remaining 21 took LTG-IR plus at least 2 other AEDs. The mean LTG-IR dose was 544 mg/day (range 150-1100 mg/day). The mean LTG-IR serum level was 11.6 (available in 53 patients-range 4.6-21 mcg/ml). Twenty six patients were converted to the same dose and one patient took a mixture of LTG-XR and LTG-IR at the same total daily dose, while 21 had their dose slightly increased and 7 had their dose slightly decreased due to adverse effects. The mean serum level after conversion was 11.8 (available in 49 patients-range 2.6-21.2 mcg/ml). As a result of the conversion, 26 patients (47%) experienced >50% reduction in seizure frequency. There was a 46% median reduction in seizure frequency overall. Seven patients reported improvement in adverse effects.

CONCLUSION

A conversion from LTG-IR to LTG-XR can help improve seizure control in some individuals with drug-resistant epilepsy, in addition to improving tolerability. While it is indicated in individuals experiencing peak adverse effects, it should also be considered in patients who have received incomplete seizure control from LTG-IR.

USL255 extended-release topiramate: dose-proportional pharmacokinetics and tolerability in healthy volunteers

Objective

Evaluate the pharmacokinetics (PK), safety, and tolerability of single doses of once-daily USL255, Qudexy XR (topiramate) extended-release capsules, over a wide dosing range.

Methods

Two single-dose, phase I studies in healthy adults were used to evaluate the PK profile and maximum tolerated dose (MTD) of USL255 from 25–1,400 mg. Standard PK parameters assessed included area under the plasma concentration-time curve (AUC) and maximum plasma concentration (C_max). Dose proportionality, linearity, and intersubject and intrasubject variability (coefficient of variation [%CV]) of AUC and C_max were evaluated. Investigator-reported adverse events (AEs) were obtained throughout the studies.

Results

After the initial increase in plasma concentration levels immediately following administration of USL255 25–1,400 mg, plasma topiramate concentration-time profiles were flat up to 24 h after dosing. AUC was dose proportional from 25–1,400 mg, and C_max was dose proportional from 50–1,400 mg; both AUC and C_max were linear across the entire dose range. Low intersubject and intrasubject %CV values were observed for AUC_0−t, AUC_0−∞, and C_max (intersubject %CV: 20.2, 19.6, and 22.4%, respectively; intrasubject %CV of dose-normalized mean values: 10.8, 8.2, and 13.2%, respectively). USL255 was generally safe and well tolerated with MTD established at 1,200 mg.

Significance

These results demonstrate that USL255 provides consistent plasma topiramate exposure across an extended-dosing interval and predictable plasma topiramate concentrations over a wide dosing range. Overall, the favorable safety profile and consistency of exposure suggest once-daily USL255 can be a useful treatment option for patients with epilepsy.

Oxcarbazepine extended-release formulation in epilepsy

Oxcarbazepine (OXC) is a 10-keto-analogue of carbamazepine, which was developed and labeled as a follow-up antiepileptic drug, that was intended to overcome some of the pharmacological drawbacks of carbamazepine with similar efficacy. The main advantage is the nonoxidative metabolic pathway that allows a lower enzyme-induction profile and fewer drug interactions. OXC is rapidly and extensively reduced by cytosolic hepatic enzymes to its monohydroxylated derivative (MHD), thus OXC may be regarded as a prodrug with MHD representing the active antiepileptic agent. The immediate-release (IR) formulation of OXC (Trileptal(®), Timox(®)) has an almost complete bioavailibilty. It is rapidly absorbed and reaches peak concentrations after 1-3 h. MHD peak concentrations are measured within 4-12 h. Elimination half-life in healthy subjects is 1-5 h for OXC and 7-20 h for MHD. The OXC plasma concentration peak may have been responsible for side effects, such as dizziness, vertigo, coordination problems or blurred vision, which appeared more often with this formulation in individual cases than with the formulation available prior to 2000, or with another formulation that has been distributed in Scandinavian countries. Both possibilities offer a profile approaching the characteristics of an extended-release (ER) formulation. ER OXC was labeled in Germany in 2008 (Apydan(®) extent, Desitin Arzneimittel GmbH, Hamburg, Germany). Under steady-state conditions, Phase I studies show bioequivalence between IR and ER OXC. With ER OXC, OXC plasma peak concentrations and both OXC and MHD peak-trough fluctuations are markedly reduced. In clinical trials, comparisons between IR OXC twice daily versus ER OXC once daily failed to show significant differences; efficacy tended to be better with IR OXC, whereas OXC ER showed insignificant tolerability advantages. Another study is currently ongoing to compare the tolerability of both formulations under twice-daily administration conditions in patients with difficult-to-treat epilepsies who require a dosage increase of OXC and who are randomized to IR or ER OXC.

Generic products of antiepileptic drugs: a perspective on bioequivalence, bioavailability, and formulation switches using Monte Carlo simulations

INTRODUCTION

Generic products of antiepileptic drugs (AEDs) are currently a controversial topic as neurologists and patients are reluctant to switch from brand products to generics and to switch between generics.

OBJECTIVE

The aim of this study was to provide enlightenment on issues of bioequivalence (BE) and interchangeability of AED products.

METHODS

Monte Carlo simulations of the classic 2 × 2 BE studies were performed to study the effect of sample size, within-subject variability, and the true difference in pharmacokinetic values of the products under comparison on BE acceptance of generic AED products. Simulations were extended to study the comparative performance of two generic AED products against the same innovative product. The simulated results are compared with literature data on AEDs.

RESULTS

The question with regard to bioavailability (BA) is whether two formulations are different, while for BE the question is whether two formulations are sufficiently similar in terms of extent and rate of absorption. Therefore, the criteria for BA and BE and the statistical analysis involved in their analysis are different. Two generic formulations that meet regulatory approval requirements for generics by being bioequivalent to the same innovative AED may not be bioequivalent to one another and therefore should not be regarded as equal or as therapeutically equivalent products. A switch from a standard or an immediate-release formulation to a modified-release product, which comprises extended-release or delayed-release formulations, should not be regarded as a switch between generics, but rather as a switch between different formulation types.

DISCUSSION

Switches between bioequivalent generic AED products could potentially lead to larger changes in plasma levels and exposure than the brand-to-generic switch. The simulation work verified the clinical findings that not all generic AED products bioequivalent to the same innovative product are bioequivalent to one another.

CONCLUSIONS

Two generic formulations that meet regulatory approval requirements for generics, by being bioequivalent to the innovative AED, may not be bioequivalent to one another. Additional BE criteria are needed for a formulation switch, particularly in epilepsy, where a breakthrough seizure may change a patient's status from seizure-free to refractory.

Comparative steady-state pharmacokinetic evaluation of immediate-release topiramate and USL255, a once-daily extended-release topiramate formulation

PURPOSE

Compare the pharmacokinetic (PK) profiles of immediate- and extended-release formulations of topiramate (TPM) in healthy subjects following multiple dosing, and evaluate maintenance of topiramate exposures after switching formulations.

METHODS

A randomized, open-label, single-center, two-way crossover, multiple-dose study comparing the steady-state PK profile of once-daily extended-release topiramate (USL255) to immediate-release topiramate (TPM-IR) administered twice-daily. The TPM PK profile was evaluated using standard PK parameters (e.g., AUC0-24 , Cmax , Cmin ) as well as less common PK criteria such as fluctuation index (FI), peak occupancy time (POT), and percent coefficient of variation (%CV). In addition, partial AUC (AUCp ) analyses provided comparisons of the AUC profiles over predetermined time intervals between TPM-IR and USL255. Pharmacokinetic equivalence between formulations was defined as containment of the 90% confidence intervals (CIs) of the USL255/TPM-IR geometric least-squares mean (GLSM) ratio within the equivalence limits of 80-125%. The effect of switching between treatments was assessed by evaluating equivalence of PK parameters between the day prior to formulation switch and the day immediately following formulation switch. Maintenance of steady state after switching formulations was also evaluated by comparing the slope between Cmin values at formulation switch and 24 h postswitch. Tolerability was evaluated through adverse event monitoring, vital sign measurements, and clinical laboratory evaluations.

KEY FINDINGS

USL255 was well tolerated and provided TPM plasma exposure equivalent to TPM-IR at various time intervals. USL255 also demonstrated a significantly lower Cmax (p < 0.001) and higher Cmin (p < 0.001), longer tmax , lower %CV, and 26% decreased FI, as compared with TPM-IR. Further, switching between TPM-IR and USL255 did not affect TPM concentrations, including Cmin , immediately after transitioning and at steady state.

SIGNIFICANCE

As compared with TPM-IR, USL255 provided equivalent plasma exposure with an extended absorption profile. Therefore, USL255 offers a once-daily alternative to twice-daily TPM-IR, with reduced TPM fluctuations.

Design and optimization of sustained-release divalproex sodium tablets with response surface methodology

Response surface methodology is defined as a collection of mathematical and statistical methods that are used to develop, improve, or optimize a product or process. In the present study, a statistical design (Mixture Design) was employed for formulation and optimization of a sustained-release hydrophilic divalproex sodium matrix tablet. Different excipients were used to improve the drug's poor flowability. The hardness of the prepared tablets and also their release pattern were tested. The formulation design was carried out employing mixture design using four excipients in three levels. The Carr's index of formulations and tensile strength were determined and analyzed using Minitab software. The suitable formulations regarding flowability and tablet tensile strength were selected by this software for subsequent drug release studies. The dissolution tests were carried out in acidic and basic phases which were previously proved to be biomimetic. Samples were analyzed using HPLC, and release data were compared to Depakine® (sustained-release divalproex from Sanofi). Release kinetics was also determined for selected formulations. Selected formulations were subjected to dissolution test and showed similar dissolution profiles with Depakine® based on difference and similarity factor calculations. The software selected an optimized formulation which had a slightly different release pattern in vitro compared to innovator but of nearly zero-order kinetics. It can be concluded that application of Mixture Design is a shortcut method to design suitable formulations of sustained-release divalproex sodium containing hydrophilic matrix tablets by direct compression method.

Extended-release antiepileptic drugs: a comparison of pharmacokinetic parameters relative to original immediate-release formulations

Many antiepileptic drugs (AEDs) have short half-lives with large fluctuations in peak-to-trough plasma concentrations. Consequences of these pharmacokinetic (PK) properties may include adverse events (AEs) and breakthrough seizures, potentially leading to poor adherence. To address these challenges, newer formulations of these AEDs have been developed using unique extended-release (ER) technologies. These technologies extend the dosing interval such that dosing frequency can be minimized, which may improve patient adherence. Available ER formulations have the potential to minimize the spikes in maximum plasma concentrations (C(max) ) at steady-state that often contribute to AEs during treatment with immediate-release (IR) products. In so doing, tolerability advantages may lead to increased AED effectiveness by improving adherence and allowing higher doses if clinically indicated. Direct PK comparison studies of IR and ER formulations (e.g., carbamazepine, divalproate sodium, lamotrigine, oxcarbazepine, levetiracetam, and phenytoin) have found that dose-normalized ER formulations may or may not be bioequivalent to their IR counterparts, but most ER formulations have a lower fluctuation index ([C(max) -C(min) ]/C(avg) ) compared with the IR versions. This results in flatter concentration-time plots. Not all ER preparations improve the various PK parameters to the same extent, and PK nuances may impact the effectiveness, tolerability, and adherence rates of various ER formulations.

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.

Effects of antiepileptic drug characteristics on medication adherence

PURPOSE

To determine whether antiepileptic drug (AED) characteristics are associated with medication adherence.

METHODS

We reviewed pharmacy and clinical records of 108 patients with epilepsy from the indigent care program at Shands-Jacksonville. We calculated the mean medication possession ratio (MMPR) for each AED. Using univariate analysis, we determined whether differences exist in the MMPR of various AEDs. We also determined whether the MMPR differs accordingly to the use of mono- or combination therapy, dosing frequency, release-type, or brand-name formulation. We employed multivariable analysis to determine if these differences persisted in the context of other demographic and clinical variables.

RESULTS

Mean medication possession ratio was higher (better) when using older AEDs, in monotherapy, and with more frequent dosing intervals. These variables remained significant on multivariable analysis.

CONCLUSION

Our findings contradict some commonly held beliefs on medication adherence and suggest that specific AED characteristics may be superseded by factors such as overall patient satisfaction with the drug regimen.

Comparative pharmacokinetic analysis of USL255, a new once-daily extended-release formulation of topiramate

PURPOSE

To compare the pharmacokinetics of USL255, a once-daily extended-release (ER) formulation of topiramate (TPM), with Topamax (immediate-release TPM) in healthy subjects after oral dosing and evaluate the effect of food on USL255 bioavailability and pharmacokinetics.

METHODS

This randomized, single-center, open-label, cross-over design study had three dosing periods separated by 21 days of washout between treatments. Thirty-six volunteers received single doses of USL255 (200 mg) in fasted and fed conditions and two doses of Topamax (100 mg) administered 12 h apart. TPM plasma samples were analyzed by liquid chromatography-mass spectroscopy. Pharmacokinetic parameters were calculated by noncompartmental methods.

KEY FINDINGS

USL255 fasted pharmacokinetic parameters [point estimate (90% confidence interval, CI) compared to Topamax] were: relative bioavailability (F) 91.2% (84-99%), peak plasma concentration (C(max)) USL255/Topamax-ratio 59% (53-65%), time to reach C(max) (t(max)) 19.5 ± 7.2 h, accumulation ratio (R(ac)) 3.9 ± 1.2, effective half-life (t(1/2,eff)) 55.7 ± 19.9 h, terminal half-life (t(1/2,z)) 80.2 ± 14.2 h, and peak-occupancy-time (POT) 12.1 ± 4.0 h. Although the F and C(max) were unaffected by food, R(ac) and t(1/2,eff) increased to 4.9 ± 0.9, and 72.5 ± 15.4 h, respectively. In contrast to t(1/2,z,) t(1/2,eff) reflects absorption rate; therefore, USL255's t(1/2,eff) was significantly longer than Topamax's t(1/2,eff) (37.1 ± 6.5 h).

SIGNIFICANCE

Although bioequivalent to Topamax in extent of absorption, USL255 had a slower absorption rate as reflected in its lower C(max) and longer t(max), larger POT and longer t(1/2,eff), and similar R(ac) values to that of Topamax (q12 h). This relative flat plasma profile allows for once-daily dosing with diminished fluctuations in TPM plasma levels. In addition, neither USL255's peak nor extent of plasma exposure of TPM was affected by food.

Pharmacotherapeutics of epilepsy: use of lamotrigine and expectations for lamotrigine extended release

The goal in managing patients with epilepsy is complete seizure freedom. Pharmacotherapeutic management of epilepsy is complicated by multiple syndromes, inter-individual differences in drug sensitivities, inter-individual differences in drug disposition, and drug interactions. Most anti-epileptic drugs (AEDs) have a therapeutic window with only a 2- to 3-fold concentration range. Extended release formulations offer advantages over their immediate release counter parts with less fluctuation in the serum concentration vs time curve and improved compliance. However, missed doses are more likely to result in prolonged “sub-therapeutic serum concentrations”. Best clinical outcome may sometimes require twice daily dosing of extended release formulations even though approved for once daily dosing, as this optimally balances pharmacokinetics against compliance. Lamotrigine (LTG) is a broad spectrum AED with efficacy in partial and generalized epilepsy syndromes and good tolerability. Its metabolism is affected by co-medications which may be inducing, neutral or inhibiting of hepatic glucuronidation. Furthermore, though the average half-life in monotherapy is about 24 hours, there is a large inter-individual variation that may, including the extremes, approach a range of 10-fold. LTG-XR is expected to decrease fluctuation of serum concentration in the presence of hepatic inducing or neutral drugs. However, optimal clinical benefit in some patients may require twice daily dosing when metabolism is rapid.

Levetiracetam Extended Release as Adjuvant Therapy for the Control of Partial-onset Seizures

Extended release (XR) formulation of levetiracetam (LEV) is approved by the Food and Drug Administration as an add-on to other antiepileptic drugs (AEDs) for adults with partial onset seizures. This is based on class-I evidence demonstrating significant seizure reduction in once daily dosing. Keppra-XR is marketed with the brand name of Keppra XR since 2008 (UCB Pharma). Its original immediate release (IR) formulation has been in the market since 2000. LEV has a unique molecular structure which is chemically unrelated to existing AEDs. The precise mechanism of action is unknown. Animal studies showed binding to synaptic vesicle protein SV2A, thought to be involved in modulating synaptic neurotransmitter release. LEV-IR is proven effective as adjunctive therapy for partial-onset seizures, primary generalized tonic-clonic seizures and myoclonic seizures. It was shown to be equivalent to carbamazepine as first-line treatment for partial-onset seizures. The extended release formulation added advantages such as better tolerance and increased compliance.

Extended-release formulations of antiepileptic drugs: rationale and comparative value

Extended-release products are designed to prolong the absorption of drugs with short half-lives, thereby allowing longer dosing intervals while minimizing fluctuations in serum drug levels. The relationship between serum drug concentration and clinical effects of antiepileptic drugs (AEDs) can be complex and reducing fluctuations in serum drug levels is not equally advantageous for all AEDs. Extended-release formulations have been shown to be particularly valuable for carbamazepine, whereas for other AEDs advantages, other than prolongation of the dosing interval, have not been clearly demonstrated. Differences in bioavailability may exist between extended-release and immediate-release formulations and among different brands of extended-release products. Therefore, when switching from one formulation to another, careful monitoring of clinical response and attention to the need for dose adjustment are warranted.

Efficacy, safety, and potential of extended-release lamotrigine in the treatment of epileptic patients

Epilepsy is a frequent, chronic disease demanding long-term medication with antiepileptic drugs (AEDs). When slow release formulations of AEDs are used the chance of compliance and control of seizures is increased. Lamotrigine (LTG) is a broad spectrum antiepileptic drug (AED), effective against both generalized and partial seizures. Its immediate-release formulation (LTG-IR) requires twice-daily dosing. In contrast, an extended-release formulation (LTG-XR) may be given once daily, providing a flatter dose-concentration curve with apparently lower maximum serum levels. Simplified dosing positively affects compliance and LTG-XR has a similar profile of efficacy and tolerability to LTG-IR. Rashes, including Stevens-Johnson syndrome, are the most serious adverse effect impacting 0.8% of pediatric patients. Thus, LTG-XR should be discontinued upon the appearance of rash.

Levetiracetam extended release and levetiracetam immediate release as adjunctive treatment for partial-onset seizures: an indirect comparison of treatment-emergent adverse events using meta-analytic techniques

The safety profiles of once-daily adjunctive levetiracetam (LEV) extended release (XR) (1000mg/day) and adjunctive LEV immediate release (IR) (500mg twice daily) were compared using data from three randomized, placebo (PBO)-controlled phase III clinical trials in patients with partial-onset seizures. MedDRA 9.0 treatment-emergent adverse events (TEAEs) were indirectly compared using meta-analytic techniques, including calculation of risk difference (RD) and mixed-effects analysis. Statistical significance was set at 10% alpha risk, the normative value for these analyses. Data from 555 patients older than 16 (204 LEV IR, 70 LEV XR, 281 PBO) were analyzed. Following adjustment for incidence of placebo TEAEs, LEV XR showed statistically significantly lower rates of TEAEs than LEV IR across nervous system disorders (RD=-18%, P=0.03), psychiatric disorders (RD=-11%, P=0.08), and metabolism and nutrition disorders (RD=-3%, P=0.08). Among nervous system disorders, the RD for headache favored LEV XR (RD=-11%, P=0.08). These results suggest that adjunctive LEV XR may be associated with a lower incidence of nervous system, psychiatric, and nutritional and metabolic TEAEs as compared with LEV IR. However, this difference was observed at a broad scale and not at a specific TEAE level except for headache.

Antiepileptic drug-induced cognitive adverse effects: potential mechanisms and contributing factors

Cognitive dysfunction is frequently observed in patients with epilepsy and represents an important challenge in the management of patients with this disorder. In this respect, the relative contribution of antiepileptic drugs (AEDs) is of relevance. The fact that a considerable number of patients require AED therapy for many years, or perhaps even a lifetime, emphasizes the need to focus on the long-term adverse effects of these drugs on cognition. The most prevalent of the CNS adverse effects observed during AED therapy are sedation, somnolence, distractibility, insomnia and dizziness. Sedation, in particular, is associated with most of the commonly used AED therapies. Nevertheless, cognitive function in individuals with epilepsy may also be influenced by several factors, of which AEDs constitute only one of many putative causes. In general terms, most studies agree that some differences exist among the older AEDs with regard to the effects on cognition, and some newer generation molecules may have a better cognitive profile than older AEDs. The mechanisms of action are an obvious determinant; however, there is still a lack of evidence for differentiation between available drugs with regard to cognitive effects. Some authors have suggested that there may be different cognitive effects associated with individual drugs; however, the question as to whether there are more specific deficits related to the action of individual drugs remains unsolved. There seems to be agreement that polytherapy and high-dose treatment can produce cognitive adverse effects and when high dosages or adjunctive polytherapy is needed, the balance between benefits and disadvantages may be negatively biased against drug treatment. Thus, drug treatment requires careful balancing in the attempt to reach maximal seizure control while avoiding neurotoxic adverse effects. Finally, the mood status of the patient and clinical relevance of the information obtained by neuropsychological testing represent important variables that need to be taken into account when discussing cognitive adverse effects of AEDs.

Once-daily extended-release levetiracetam as adjunctive treatment of partial-onset seizures in patients with epilepsy: a double-blind, randomized, placebo-controlled trial

PURPOSE

Double-blind randomized trial to assess efficacy and tolerability of once-daily extended-release levetiracetam (LEV XR) tablets (2 x 500 mg) as add-on therapy in patients (12-70 years old) with partial-onset seizures (POS) refractory to one to three antiepileptic drugs.

METHODS

After an 8-week prospective baseline-period, eligible patients were randomized (1:1) to once-daily LEV XR 1,000 mg/day or placebo for 12 weeks. Evaluations included changes from baseline in POS-frequency/week, responders (>or=50% reduction in POS-frequency/week), seizure-freedom, adverse events, laboratory tests, physical and neurologic examinations, vital signs, body-weight, and 12-lead electrocardiogram.

RESULTS

Of 188 patients screened, 158 were randomized (intention-to-treat population): LEV XR (n = 79) or placebo (n = 79). Seventy-one (89.9%) LEV XR and 72 (91.1%) placebo patients completed the trial. Median POS-frequency/week reduction was 46.1% on LEV XR and 33.4% on placebo. Estimated reduction with LEV XR over placebo was 14.4% (p = 0.038). Thirty-four (43%) LEV XR and 23 (29.1%) placebo patients experienced >or=50% reduction in POS-frequency/week. Eight (10.1%) patients receiving LEV XR and one (1.3%) receiving placebo were free of POS during the 12-week treatment period. Forty-one (53.2%) LEV XR and 43 (54.4%) placebo patients reported >or=1 adverse event. Adverse events reported with an incidence >5% and seen more often with LEV XR than with placebo were somnolence, influenza, irritability, nasopharyngitis, dizziness, and nausea.

DISCUSSION

Once-daily LEV XR 1,000 mg was effective and well-tolerated as adjunct therapy in patients with POS. Ten percent of patients randomized to LEV XR experienced freedom from POS. These results support the clinical value of this new LEV XR formulation.

Pharmacokinetics of levetiracetam XR 500mg tablets

PURPOSE

To compare the relative bioavailability of levetiracetam extended-release tablets (XR) with immediate release tablets (IR) following single and multiple dosing; to assess the food effect and the dose-proportionality of XR from 1000 to 3000mg.

METHODS

Two panels of 24 healthy subjects were enrolled. Study N01160 was a three-way crossover between IR fasted (single and repeated 500mg b.i.d.), XR fasted (single and repeated 1000mg o.d.) and XR with food (1000mg single dose). Study N01260 was a three-way crossover single dose-proportionality between XR 1000, 2000 and 3000mg.

RESULTS

After single dose, levetiracetam XR and IR were bioequivalent with respect to AUC((0-t)), AUC(infinity) and C(max). The median t(max) was delayed from 0.9 to 4h. For the fed/fasted comparison, the confidence intervals around the C(max) and AUC ratios were within the 80-125% limits. At steady-state, the AUC(24h) were also bioequivalent. In the dose-proportionality trial, the AUC and C(max) increased linearly with the dose. Levetiracetam XR was well tolerated.

CONCLUSIONS

Levetiracetam XR 1000mg o.d. is bioequivalent to levetiracetam IR 500mg b.i.d. There is no food effect, and the absorption of XR is dose-proportional from 1000 to 3000mg.