Intramuscular and intravenous levetiracetam in humans: safety and pharmacokinetics

Bioequivalence and Safety of Levetiracetam Granules and Oral Solution: A Randomized, Single-Dose, 2-Period Crossover Study in Healthy Chinese Volunteers Under a Fasting Condition

The bioequivalence and safety of levetiracetam granules (test formulation) and oral solution (reference formulation) were evaluated in Chinese healthy volunteers under a fasting condition. A total of 24 subjects randomly received the test or reference formulation at the rate of 1:1. The alternative formulation was administered after a 7-day washout period. The blood samples were collected at designated time points. Liquid chromatography-tandem mass spectrometry was applied to determine the plasma concentrations of levetiracetam. Adverse events were monitored and recorded. The 90% CIs for the geometric mean ratios of maximum plasma concentration, area under the plasma concentration-time curve from time 0 to the last quantifiable concentration, and area under the plasma concentration-time curve from time 0 to infinity between test preparation and reference preparation were 95.5% to 110.7%, 100.2% to 105.3%, and 100.3% to 105.7%, respectively, all within an acceptable bioequivalence range of 80.00% 125.00%. Both test and reference preparations were well tolerated. The trial confirmed that a single dose of 500-mg levetiracetam granules was bioequivalent to oral solution under a fasting condition, and may serve as a new dosage form of levetiracetam for clinical practice.

A critical review of fosphenytoin sodium injection for the treatment of status epilepticus in adults and children

INTRODUCTION

Status epilepticus (SE) is a neurological emergency that can occur in patients with or without epilepsy. Rapid treatment is paramount to mitigate risks of neuronal injury, morbidity/mortality, and healthcare-cost burdens associated with SE. Fosphenytoin is the prodrug of phenytoin designed to enable faster administration and improved tolerability as compared to intravenous (IV) phenytoin in the treatment of SE.

AREAS COVERED

This review evaluates the chemistry, pharmacokinetics, pharmacodynamics, safety, and tolerability of fosphenytoin. Efficacy data for fosphenytoin in the treatment of SE in adults and children are analyzed from initial phase I trials in 1988 through current phase III trials, including the Established Status Epilepticus Treatment Trial (ESETT).

EXPERT OPINION

IV phenytoin is an established treatment of SE, but its alkaline aqueous vehicle is associated with dermatologic irritation and systemic complications when rapidly infused. The water-soluble nature of its prodrug, fosphenytoin, allows for rapid infusion, and it is rapidly converted to phenytoin when administered intravenously or intramuscularly. In the ESETT, IV fosphenytoin demonstrated similar efficacy in treatment of established SE when compared to IV levetiracetam and IV valproate in adults and children, making it a reasonable choice in the treatment of SE that is unresponsive to benzodiazepines.

An update in the initial management of paediatric status epilepticus

PURPOSE OF REVIEW

Over the last 2 years, algorithms for the optimal management of status epilepticus have changed, as the medical community has recognized the need to terminate seizures in status in a timely manner. Recent research has evaluated the different choices of benzodiazepine and has given consideration to second-line treatment options.

RECENT FINDINGS

There has been a move to examine alternatives to phenytoin (such as levetiracetam and lacosamide) as second-line agents. Valproate should be used cautiously in view of the potential side effects. Three ongoing trials [Established Staus Epilepticus Treatment Trial (ESETT), Convulsive Status Epilepticus Paediatric Trial (ConSEPT), and emergency treatment with levetiracetam or phenytoin in status epilepticus in children (EcLiPSE)] are comparing the efficacy of levetiracetam and phenytoin.

SUMMARY

Benzodiazepines remain the first-line agent of choice, although there is ongoing discussion about the mode of administration and the best drug to choose. The results of ESETT, ConSEPT, and EcLiPSE will affect our future management of status, as we give consideration to levetiracetam as an alternative to phenytoin. Other medications such as lacosamide may emerge in future algorithms too.

Intravenous and Intramuscular Formulations of Antiseizure Drugs in the Treatment of Epilepsy

Intravenous and intramuscular antiseizure drugs (ASDs) are essential in the treatment of clinical seizure emergencies as well as in replacement therapy when oral administration is not possible. The parenteral formulations provide rapid delivery and complete (intravenous) or nearly complete (intramuscular) bioavailability. Controlled administration of the ASD is feasible with intravenous but not intramuscular formulations. This article reviews the literature and discusses the chemistry, pharmacology, pharmacokinetics, and clinical use of currently available intravenous and intramuscular ASD formulations as well as the development of new formulations and agents. Intravenous or intramuscular formulations of lorazepam, diazepam, midazolam, and clonazepam are typically used as the initial treatment agents in seizure emergencies. Recent studies also support the use of intramuscular midazolam as easier than the intravenous delivery of lorazepam in the pre-hospital setting. However, benzodiazepines may be associated with hypotension and respiratory depression. Although loading with intravenous phenytoin was an early approach to treatment, it is associated with cardiac arrhythmias, hypotension, and tissue injury at the injection site. This has made it less favored than fosphenytoin, a water-soluble, phosphorylated phenytoin molecule. Other drugs being used for acute seizure emergencies are intravenous formulations of valproic acid, levetiracetam, and lacosamide. However, the comparative effectiveness of these for status epilepticus (SE) has not been evaluated adequately. Consequently, guidelines for the medical management of SE continue to recommend lorazepam followed by fosphenytoin, or phenytoin if fosphenytoin is not available. Intravenous solutions for carbamazepine, lamotrigine, and topiramate have been developed but remain investigational. The current ASDs were not developed for use in emergency situations, but were adapted from ASDs approved for chronic oral use. New approaches for bringing drugs from experimental models to treatment of human SE are needed.

Intramuscular and rectal therapies of acute seizures

The intramuscular (IM) and rectal routes are alternative routes of delivery for antiepileptic drugs (AEDs) when the intravenous route is not practical or possible. For treatment of acute seizures, the AED used should have a short time to maximum concentration (Tmax). Some AEDs have preparations that may be given intramuscularly. These include the benzodiazepines (diazepam, lorazepam, and midazolam) and others (fosphenytoin, levetiracetam). Although phenytoin and valproate have parenteral preparations, these should not be given intramuscularly. A recent study of prehospital treatment of status epilepticus evaluated a midazolam (MDZ) autoinjector delivering IM drug compared to IV lorazepam (LZP). Seizures were absent on arrival to the emergency department in 73.4% of the IM MDZ compared to a 63.4% response in LZP-treated subjects (p < 0.001 for superiority). Almost all AEDs have been evaluated for rectal administration as solutions, gels, and suppositories. In a placebo-controlled study, diazepam (DZP) was administered at home by caregivers in doses that ranged from 0.2 to 0.5 mg/kg. Diazepam was superior to placebo in reduced seizure frequency in children (p < 0.001) and in adults (p = 0.02) and time to recurrent seizures after an initial treatment (p < 0.001). Thus, at this time, only MZD given intramuscularly and DZP given rectally appear to have the properties required for rapid enough absorption to be useful when intravenous routes are not possible. Some drugs cannot be administered rectally owing to factors such as poor absorption or poor solubility in aqueous solutions. The relative rectal bioavailability of gabapentin, oxcarbazepine, and phenytoin is so low that the current formulations are not considered to be suitable for administration by this route. When administered as a solution, diazepam is rapidly absorbed rectally, reaching the Tmax within 5-20 min in children. By contrast, rectal administration of lorazepam is relatively slow, with a Tmax of 1-2h. The dependence of gabapentin on an active transport system, and the much-reduced surface area of the rectum compared with the small intestine, may be responsible for its lack of absorption from the rectum. This article is part of a Special Issue entitled "Status Epilepticus".

Clinical pharmacology and pharmacokinetics of levetiracetam

Status epilepticus and acute repetitive seizures still pose a management challenge despite the recent advances in the field of epilepsy. Parenteral formulations of old anticonvulsants are still a cornerstone in acute seizure management and are approved by the FDA. Intravenous levetiracetam (IV LEV), a second generation anticonvulsant, is approved by the FDA as an adjunctive treatment in patients 16 years or older when oral administration is not available. Data have shown that it has a unique mechanism of action, linear pharmacokinetics and no known drug interactions with other anticonvulsants. In this paper, we will review the current literature about the pharmacology and pharmacokinetics of IV LEV and the safety profile of this new anticonvulsant in acute seizure management of both adults and children.

Current oral and non-oral routes of antiepileptic drug delivery

Antiepileptic drugs are commonly given orally for chronic treatment of epilepsy. The treatment of epilepsy requires administration of medications for both acute and chronic treatment using multiple types of formulations. Parenteral routes are used when the oral route is unavailable or a rapid clinical response is required. Lorazepam and midazolam can be administered by the buccal, sublingual or intranasal routes. Consensus documents recommend rectal diazepam, buccal midazolam or intranasal midazolam for the out-of-hospital treatment of early status epilepticus. In the United States, diazepam is the only FDA approved rectal formulation. With the lack of parenteral, buccal or intranasal formulations for many of the antiepileptic drugs, the use of the rectal route of delivery to treat acute seizures or to maintain therapeutic concentrations is suitable for many, but not all antiepileptic medications. There is a significant need for new non-oral formulations of the antiepileptic drugs when oral administration is not possible.