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Objective: This study was undertaken to describe patterns of benzodiazepine use as first‐line treatment of status epilepticus (SE) and test the association of benzodiazepine doses with response to second‐line agents in patients enrolled in the Established Status Epilepticus Treatment Trial (ESETT). Methods: Patients refractory to an adequate dose of benzodiazepines for the treatment of SE were enrolled in ESETT. Choice of benzodiazepine, doses given prior to administration of second‐line agent, route of administration, setting, and patient weight were characterized. These were compared with guideline‐recommended dosing. Logistic regression was used to determine the association of the first dose of benzodiazepine and the cumulative benzodiazepine dose with the response to second‐line agent. Results: Four hundred sixty patients were administered 1170 doses of benzodiazepines (669 lorazepam, 398 midazolam, 103 diazepam). Lorazepam was most frequently administered intravenously in the emergency department, midazolam intramuscularly or intravenously by the emergency medical services personnel, and diazepam rectally prior to ambulance arrival. The first dose of the first benzodiazepine (N = 460) was lower than guideline recommendations in 76% of midazolam administrations and 81% of lorazepam administrations. Among all administrations, >85% of midazolam and >76% of lorazepam administrations were lower than recommended. Higher first or cumulative benzodiazepine doses were not associated with better outcomes or clinical seizure cessation in response to second‐line medications in these benzodiazepine‐refractory seizures. Significance: Benzodiazepines as first‐line treatment of SE, particularly midazolam and lorazepam, are frequently underdosed throughout the United States. This broad and generalizable cohort confirms prior single site reports that underdosing is both pervasive and difficult to remediate. (ESETT ClinicalTrials.gov identifier: NCT01960075.) [ABSTRACT FROM AUTHOR]

The Established Status Epilepticus Treatment Trial was a blinded, comparative‐effectiveness study of fosphenytoin, levetiracetam, and valproic acid in benzodiazepine‐refractory status epilepticus. The primary outcome was clinical seizure cessation and increased responsiveness without additional anticonvulsant medications. Weight‐based dosing was capped at 75 kg. Hence, patients weighing >75 kg received a lower mg/kg dose. Logistic regression models were developed in 235 adults to determine the association of weight (≤ or >75 kg, ≤ or >90 kg), sex, treatment, and weight‐normalized dose with the primary outcome and solely seizure cessation. The primary outcome was achieved in 45.1% and 42.5% of those ≤75 kg and >75 kg, respectively. Using univariate analyses, the likelihood of success for those >75 kg (odds ratio [OR] = 0.9, 95% confidence interval [CI] = 0.54‐1.51) or >90 kg (OR = 0.85, 95% CI = 0.42‐1.66) was not statistically different compared with those ≤75 kg or ≤90 kg, respectively. Similarly, other predictors were not significantly associated with primary outcome or clinical seizure cessation. Our findings suggest that doses, capped at 75 kg, likely resulted in concentrations greater than those needed for outcome. Studies that include drug concentrations and heavier individuals are needed to confirm these findings. [ABSTRACT FROM AUTHOR]

Summary: A subgroup of patients with drug‐resistant epilepsy have seizure clusters, which are a part of the continuum of seizure emergencies that includes prolonged episodes and status epilepticus. When the patient or caregiver can identify the beginning of a cluster, the condition is amenable to certain treatments, an approach known as rescue therapy. Intravenous drug administration offers the fastest onset of action, but this route is usually not an option because most seizure clusters occur outside of a medical facility. Alternate routes of administration have been used or are proposed including rectal, buccal, intrapulmonary, subcutaneous, intramuscular, and intranasal. The objective of this narrative review is to describe the (1) anatomical, physiologic, and drug physicochemical properties that need to be considered when developing therapies for seizure emergencies and (2) products currently in development. New therapies must consider parameters of Fick's law such as absorptive surface area, blood flow, membrane thickness, and lipid solubility, because these factors affect both rate and extend of absorption. For example, the lung has a 50 000‐fold greater absorptive surface area than that associated with a subcutaneous injection. Lipid solubility is a physicochemical property that influences the absorption rate of small molecule drugs. Among drugs currently used or under development for rescue therapy, allopregnanolone has the greatest lipid solubility at physiologic pH, followed by propofol, midazolam, diazepam, lorazepam, alprazolam, and brivaracetam. However, greater lipid solubility correlates with lower water solubility, complicating formulation of rescue therapies. One approach to overcoming poor aqueous solubility involves the use of a water‐soluble prodrug coadministered with a converting enzyme, which is being explored for the intranasal delivery of diazepam. With advances in seizure prediction technology and the development of drug delivery systems that provide rapid onset of effect, rescue therapies may prevent the occurrence of seizures, thus greatly improving the management of epilepsy. [ABSTRACT FROM AUTHOR]

Objective Canine status epilepticus ( CSE) has potential as a translational platform to evaluate the safety and efficacy of novel compounds and inform human status epilepticus trials. The aim of this study was to determine the intravenous dose of fosphenytoin ( FOS) needed for dogs in a CSE clinical trial to attain phenytoin ( PHT) concentrations similar to those used for human status epilepticus and monitor PHT concentrations. Methods Four healthy dogs were used to characterize PHT pharmacokinetics. Each received either 15 mg/kg or 25 mg/kg of PHT equivalent intravenously. Blood samples were collected and FOS (total) and derived PHT (total and unbound) plasma concentrations were measured using high-performance liquid chromatography-mass spectrometry (HPLC-MS). Noncompartmental pharmacokinetics ( PK) parameter values were determined and compartmental PK modeling and simulations were used to select the dose for the clinical trial with a target goal of 1-2 μg/ml unbound PHT at 30-60 min postinfusion. Predicted total and unbound PHT concentrations were compared with concentrations in blood collected from dogs treated for CSE in the clinical trial. Results Initial estimates suggested that a loading dose of 25 mg/kg would attain unbound concentrations of 1-2 μg/ml; however, this dose produced concentrations above 3-6 μg/ml, which resulted in clinically significant toxicity. A two-compartment model best fit the PHT concentration data with alpha-phase half-life of 2-5 min and elimination half-life of ~5 h. Based on the simulations, a dose of 15 mg/kg was selected and used in the clinical trial and 15 of 16 dogs randomized to the treatment arm had PHT plasma concentrations within the goal range. Significance This study demonstrates that characterization of pharmacokinetics in a small number of dogs is useful in determining dosage regimens designed to attain targeted concentrations in clinical trials. Using this approach, we were able to determine a safe and effective dose of FOS for a clinical trial of CSE. [ABSTRACT FROM AUTHOR]

Objectives There are a limited number of marketed intravenous antiepileptic drugs (AEDs) available to treat status epilepticus (SE). All were first developed for chronic therapy of epilepsy, not specifically for SE. Epilepsy and canine SE (CSE) occur naturally in dogs, with prevalence, presentation, and percentage of refractory cases similar to human epilepsy. The objective of this study was to determine if CSE treated with fosphenytoin (FOS) results in a similar responder rate as for people. Methods A randomized clinical trial was performed for dogs with CSE. Dogs who presented during a seizure or who had additional seizures after enrolling received intravenous (i.v.) benzodiazepine (BZD) followed immediately by intravenous infusion of 15 mg/kg phenytoin equivalent (PE) of fosphenytoin (FOS) or saline placebo (PBO). If seizures continued, additional AEDs were administered per the standard of care for veterinary patients. Total and unbound plasma phenytoin (PHT) concentrations were measured. Results Consent was obtained for 50 dogs with CSE. Thirty-one had additional motor seizures and were randomized to the study intervention (22 FOS and 9 PBO). There was a statistically significant difference in the 12 h responder rate, with 63% in the FOS group versus 22% in the placebo group (p = 0.043) having no further seizures. The unbound PHT concentrations at 30 and 60 min were within the therapeutic concentrations for people (1-2 μg/ml) with the exception of one dog. There was mild vomiting in 36% of the FOS group (7/22) within 20 min of FOS administration and none of the placebo group (0/9) (p = 0.064). Significance This proof of concept study provides the first evidence that FOS is tolerated and effective in canine SE at PHT concentrations clinically relevant for human SE. Furthermore, naturally occurring CSE can be utilized as a translational platform for future studies of novel SE compounds. [ABSTRACT FROM AUTHOR]

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 (Cmax). Dose proportionality, linearity, and intersubject and intrasubject variability (coefficient of variation [% CV]) of AUC and Cmax 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 Cmax was dose proportional from 50-1,400 mg; both AUC and Cmax were linear across the entire dose range. Low intersubject and intrasubject % CV values were observed for AUC0−t, AUC0−∞, and Cmax (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. A PowerPoint slide summarizing this article is available for download in the Supporting Information section . [ABSTRACT FROM AUTHOR]

Purpose Although oral topiramate ( TPM) products are widely prescribed for migraines and epilepsy, injectable TPM is not available for human use. We have developed a solubilized TPM formulation using a cyclodextrin matrix, Captisol with the long-term goal of evaluating its safety and efficacy in neonatal seizures. This study in healthy adult volunteers was performed as required by the U.S. Food and Drug Administration ( FDA) to demonstrate the pharmacokinetics and safety prior to initiation of studies involving children. This study allowed investigation of absolute bioavailability, absolute clearance, and distribution volume of TPM, information that could not be obtained without using an intravenous TPM formulation. Methods This study was an open-label, two-way crossover of oral and intravenous TPM in 12 healthy adult volunteers. Initially two subjects received 50 mg, intravenously and orally. Following evidence of safety in the first two subjects, 10 individuals received 100 mg doses of intravenous and oral TPM randomly sequenced 2 weeks apart. Blood samples were taken just prior to drug administration and at intervals up to 120 h afterwards. TPM was measured using a validated liquid chromatography-mass spectrometry method. Concentration-time data were analyzed using a noncompartmental approach with Win Nonlin 5.2. Key Findings All subjects completed the study. The mean (±standard deviation) absolute oral bioavailability was 109% (±10.8%). For intravenous and oral TPM the mean distribution volumes were 1.06 L/kg (±0.29) and 0.94 L/kg (±0.24). Clearances were 1.33 L/h (±0.26) and 1.22 L/h (±0.26). The half-life values were 42.3 h (±6.2) and 41.2 h (±7.5). No changes in heart rate, blood pressure, electrocardiography, or infusion site reactions were observed. Mild central nervous system cognitive adverse events and ataxia occurred between dosing and 2 h post dose with both intravenous and oral administration. With intravenous TPM, these adverse effects occurred as early as during the 15-min intravenous infusion. Significance In healthy adults, oral TPM is bioequivalent to intravenous TPM, and infusion of 50-100 mg over 15 min is safe. Neurologic effects occurred during the infusion, demonstrating that TPM rapidly diffuses into the brain, which supports its evaluation for neonatal seizures. Results from this pilot study will inform the design of subsequent studies in children and newborns, including controlled clinical trials intended to assess the efficacy and safety of intravenous TPM for neonatal seizures. In addition, our results provide support for the further development of intravenous TPM as bridge therapy for older children and adults in whom oral TPM therapy is interrupted. [ABSTRACT FROM AUTHOR]

Purpose Although topiramate is widely prescribed for epilepsy and migraine, there is no intravenous product. We have developed an injectable topiramate formulation in which the drug is solubilized in a cyclodextrin matrix, Captisol® (Ligand Pharmaceuticals, Inc., La Jolla, CA). Our long-term goal is to evaluate intravenous topiramate for the treatment of neonatal seizures. Prior to studies in newborns, we carried out an investigation of injectable topiramate's safety and pharmacokinetics in adult patients. Methods Twenty adult volunteers with epilepsy or migraine on stable, on maintenance topiramate therapy were given 25 mg of a stable-labeled intravenous topiramate over 10 min, followed by their usual oral doses. Vital signs were taken, electrocardiography studies ( ECGs) were recorded, and the infusion sites were periodically examined prior to and up to 24 h after dosing. Blood samples were collected prior to administration and serially for 96 h thereafter. Plasma concentrations of both stable-labeled and regular topiramate were measured using liquid chromatography-mass spectrometry (LC-MS). Concentration-time data were analyzed using a noncompartmental approach with WinNonlin 5.2 (Pharsight Corporation, Mountain View, CA, U.S.A.). Key Findings Seven patients experienced one or more of the following minor adverse events including nausea and vomiting (1), tingling around the lips (1), paresthesia in the arms and legs (1), and a mild vasovagal response with intravenous catheter placement (1). Included in the adverse events were four patients with epilepsy who had seizures consistent with their histories. There were no changes in heart rate, blood pressure, or ECG results, and there were no infusion site reactions. Pharmacokinetic parameters (mean ± standard deviation [ SD]) determined following the intravenous dose included absolute bioavailability: 110 ± 16%, distribution volume: 0.79 ± 0.22 L/kg, clearance: 2.03 ± 1.07 L/h, and elimination half-life: 27.6 ± 9.7 h. Distribution volume, half-life, and clearance were significantly altered by enzyme-inducing drugs. Significance A single 25-mg dose of intravenous topiramate caused minimal infusion site or systemic adverse effects in patients taking oral topiramate. Pharmacokinetic results show that oral topiramate is completely absorbed and that its steady-state elimination half-life is longer than previously assumed, which permits once or twice daily dosing even in the presence of enzyme-inducing drugs. The information from this study can inform the design of subsequent studies in adults, older children, and newborns, including controlled clinical trials intended to determine the efficacy and safety of intravenous topiramate for neonatal seizures. [ABSTRACT FROM AUTHOR]

Summary Current treatment of human status epilepticus (SE) relies on drugs developed for chronic treatment of epilepsy. Many potent compounds have been discovered in animal models of SE. But they may never be useful for chronic treatment of epilepsy and thus not available for human use. Naturally occurring canine SE may become a translational platform for evaluating these compounds for eventual use in human trials. A pilot study of levetiracetam in canine SE demonstrated a 56% response rate compared to 10% for placebo. Based on these results we have obtained an NIH R-21 to further evaluate canine SE as a translational platform for developing new approaches for treating human SE. [ABSTRACT FROM AUTHOR]

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

The article focuses on various principle studies carried on canine status epilepticus (SE). It reports the availability and development of several antiepileptic drugs including levetiracetam, lacosamide, carbamazepine and topiramate which have advantages over conventional therapies to cure SE. It lists several advantages of these drugs when tested on dogs. It further reports the development of the Neurological Emergencies Treatment Trial Network in the U.S. to facilitate the studies for SE.