Fosphenytoin may cause hemodynamically unstable bradydysrhythmias

Cardiac adverse effects of antiseizure medications

INTRODUCTION

Patients with severe epilepsy are at increased risk of cardiovascular disease and arrhythmias. Although antiseizure medications (ASMs) may have indirect protective effects against cardiovascular events by reducing seizure frequency and hence sudden death in epilepsy, some of them exert cardiotoxic effects.

AREAS COVERED

Patients with epilepsy, mainly those with severe forms, are at higher risk of cardiac disease because their heart can have structural alterations and electrical instability as a consequence of repeated seizures. Some ASMs have direct protective effects through anti-inflammatory, antioxidant, hypotensive, and lipid-reducing properties. Antiseizure medications can also have toxic cardiac effects including both long-term consequences, such as the increased risk of atherogenesis and subsequent cardiovascular disease due to the influence on lipid profile and pro-inflammatory milieu, and immediate effects as the increased risk of potentially fatal arrhythmias due to the influence on ion channels. Sodium channel blocking ASMs may also affect cardiac sodium channels and this effect is particularly observed in subjects with genetic mutations in cardiac ion channels. Fenfluramine cause valvulopathies in obese subjects and this effect need to be evaluated in epilepsy patients.

EXPERT OPINION

For the selection of treatment, cardiotoxic effects of ASMs should be considered; cardiac monitoring of treatment is advisable.

Treating Status Epilepticus: Phenytoin Versus Levetiracetam

For decades, phenytoin has been the drug of choice for the treatment of epilepsy but also the second-line treatment for status epilepticus (SE). However, newer antiepileptic drugs (AEDs) have emerged as safer alternatives for the suppression of seizures. Consequently, phenytoin has recently fallen under scrutiny in the research world, prompting many studies to compare its efficacy to these other drugs, most notably levetiracetam. Levetiracetam is a second-generation AED, which is gaining wide clinical use as the second-line agent in treating SE patients. This review focuses on several clinical studies that have directly compared the effectiveness of phenytoin and levetiracetam in suppressing SE seizure activity. Additionally, this review highlights several advantages of using levetiracetam over phenytoin in this clinical context.

Recommandations Formalisées d’Experts SRLF/SFMU : Prise en charge des états de mal épileptiques en préhospitalier, en structure d’urgence et en réanimation dans les 48 premières heures (A l’exclusion du nouveau-né et du nourrisson)

La Société de réanimation de langue française et la Société française de médecine d’urgence ont décidé d’élaborer de nouvelles recommandations sur la prise en charge de l’état mal épileptique (EME) avec l’ambition de répondre le plus possible aux nombreuses questions pratiques que soulèvent les EME : diagnostic, enquête étiologique, traitement non spécifique et spécifique. Vingt-cinq experts ont analysé la littérature scientifique et formulé des recommandations selon la méthodologie GRADE. Les experts se sont accordés sur 96 recommandations. Les recommandations avec le niveau de preuve le plus fort ne concernent que l’EME tonico-clonique généralisé (EMTCG) : l’usage des benzodiazépines en première ligne (clonazépam en intraveineux direct ou midazolam en intramusculaire) est recommandé, répété 5 min après la première injection (à l’exception du midazolam) en cas de persistance clinique. En cas de persistance 5 min après cette seconde injection, il est proposé d’administrer la seconde ligne thérapeutique : valproate de sodium, (fos-)phénytoïne, phénobarbital ou lévétiracétam. La persistance avérée de convulsions 30 min après le début de l’administration du traitement de deuxième ligne signe l’EMETCG réfractaire. Il est alors proposé de recourir à un coma thérapeutique au moyen d’un agent anesthésique intraveineux de type midazolam ou propofol. Des recommandations spécifiques à l’enfant et aux autres EME sont aussi énoncées.

Phenytoin versus fosphenytoin for second-line treatment of status epilepticus: propensity score matching analysis using a nationwide inpatient database

PURPOSE

For status epilepticus, the choice of antiepileptic drugs for second-line treatment after benzodiazepine remains controversial: phenytoin or fosphenytoin are recommended, however, it has been unknown which is better. Using a nationwide database, we compared the efficacy and safety of them.

METHOD

An observational study conducted with the Japanese Diagnosis Procedure Combination inpatient database identified adult patients who had been admitted for status epilepticus and who had received intravenous diazepam on the day of admission from January 1, 2011 through December 31, 2015. Propensity score matching was applied to compare outcomes of the phenytoin and fosphenytoin groups.

RESULTS

The analysis examined data of 5265 patients: 2969 patients received phenytoin; 2296 received fosphenytoin, on the day of admission. One-to-one propensity score matching created 1871 matched pairs. No significant difference was found for vasopressor use on the day of admission (4.2 % vs. 4.4 %; odds ratio 1.07; 95 % confidence intervals 0.77-1.48; p = 0.69), or for mechanical ventilation on the day of admission, in-hospital mortality, length of hospital stay, or total hospitalization cost. Higher age, comorbidity of cardiac diseases and lower body mass index were associated significantly with increased vasopressor use, whereas the dose of phenytoin equivalents and the choice of fosphenytoin were not.

CONCLUSIONS

This nationwide observational study found no evidence that fosphenytoin provides higher efficacy or safety than phenytoin for treatment of status epilepticus in adults after diazepam. Age, cardiac disease and low body mass index were identified as independent risk factors for vasopressor use in both phenytoin and fosphenytoin.

Antiepileptic Overdose

Antiepileptics include various groups of drugs that have different mechanisms of actions and adverse effects. They are often also used to treat other disorders such as psychosis, chronic pain, and migraine. The most common drugs implicated in overdose include phenytoin, sodium valproate, carbamazepine, and phenobarbital. Common signs of toxicity of these drugs are central nervous system manifestations such as altered sensorium, lethargy, ataxia, and nystagmus. Some ingestions can paradoxically precipitate seizures and even status epilepticus. Sodium valproate can cause hyperammonemic encephalopathy and cerebral edema. Carbamazepine is implicated in cardiac arrhythmias and hyponatremia. Phenobarbital causes sedation, respiratory depression, and hypotension. In suspected overdose, apart from the routine laboratory tests, serum levels of the drug should be sent. Serial levels should be measured, as drug toxicity can be prolonged. Treatment of all these overdoses begins with stabilization of airway, breathing, and circulation, and endotracheal intubation being performed to protect the airway in patients with altered mental status. For decontamination, a single dose of activated charcoal should be given. Multidose of activated charcoal may be useful in phenytoin, carbamazepine, and phenobarbital overdose. Naloxone and carnitine are indicated in valproate overdose. Carbamazepine overdose can cause a widened QRS complex and arrhythmias, which can be treated with sodium bicarbonate. Forced alkaline diuresis is no longer advocated for phenobarbital poisoning. The Extracorporeal Treatments in Poisoning (EXTRIP) workgroup have formulated guidelines for extracorporeal removal of all these drugs. In most cases, hemodialysis is preferred. Other modalities include charcoal hemoperfusion (especially for carbamazepine) or continuous venovenous hemodialysis. Patients who ingest long-acting preparations should be monitored for longer periods.

Cardiac Collapse Secondary to Phenytoin Toxicity in a Neonate Treated with Extracorporeal Membrane Oxygenation Support (ECMO)

INTRODUCTION

Although medication toxicity is uncommon in neonates, there are several medications used in this population that pose a risk. Phenytoin has an increased risk of toxicity given its narrow therapeutic window and variations in drug elimination.

CASE REPORT

We describe the case of a 3-day-old male infant who developed cardiovascular collapse secondary to severe phenytoin toxicity (max phenytoin level 86 μg/mL) and was placed on extracorporeal membrane oxygenation support (ECMO). Several ancillary treatments were utilized in an attempt to decrease serum phenytoin concentrations and limit toxicity including albumin boluses, phenobarbital administration, intravenous lipid infusion, and folic acid supplementation.

DISCUSSION

Although uncommon, drug toxicity should be considered in patients with acute changes who are exposed to medications with potential toxicity. With elevated levels of phenytoin, the half-life can be prolonged resulting in longer exposure to elevated levels of the drug as seen in our patient. This case report highlights the importance of ECMO utilization for cardiac support in neonates with medication toxicity and other potential ancillary treatments to decrease serum phenytoin concentrations.

A new method for simultaneous quantification of fosphenytoin, phenytoin and its primary metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin in whole blood by ultra-performance liquid chromatography-tandem mass spectrometry

A method for simultaneous quantification of fosphenytoin (F-PHT), phenytoin (PHT) and its main metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) in whole blood was developed and validated using ultra-performance liquid chromatography-tandem mass spectrometry. Whole blood samples were pretreated by liquid-liquid extraction with acetonitrile and methanol. Chromatographic separation was performed using a CORTECS™ UPLC® C18 (2.1 × 50 mm i.d., particle size 1.6 μm) analytical column, and water containing 10 mM ammonium formate and acetonitrile as the mobile phase. Quantification of the analytes was carried out using mass chromatography with each product ion referenced against phenytoin-d₁₀ as an internal standard. Calibration curves exhibited good linear relationships in a range from 0.005 to 50 μg/ml with correlation coefficients exceeding 0.995. The limits of detection were estimated to be 0.002-0.01 μg/ml. The accuracies and precisions were 96.2-104.3% and 0.7-10.7%, respectively. The recovery efficiencies were in the range of 42.4-59.2%. Matrix effects were observed for PHT and HPPH, with signal suppression ranging from -6.6 to -32.2%. Matrix effect for F-PHT (-5.0 to 8.9%) was less than those for PHT and HPPH. All analytes were stable under different storage conditions. This method was successfully applied for the quantification of F-PHT, PHT and HPPH in rat whole blood samples taken after bolus intravenous administration of F-PHT.

Systemic Complications Following Status Epilepticus

PURPOSE OF REVIEW

Status epilepticus (SE) is a multisystem disorder. Initially, complications of a massive catecholamine release followed by the side effects of medical therapies, impact patients' outcomes. The aim of this article is to provide an updated summary of the systemic complications following SE.

RECENT FINDINGS

In recent years, the importance of the multifaceted nature of SE and its relationship with clinical outcomes has been increasingly recognized. The cumulative systemic effects of prolonged seizures and their treatment contribute to morbidity and mortality in this condition. Most systemic complications after SE are predictable. Anticipating their occurrence and respecting a number of simple guidelines may improve the prognosis of these patients.

Status Epilepticus in Adults: A Review of Diagnosis and Treatment

Status epilepticus is a medical emergency that requires rapid diagnosis and treatment. Nonconvulsive status epilepticus is frequently underdiagnosed and therefore undertreated, which can lead to permanent neuronal damage resulting in disability or death. Despite the frequent occurrence and morbidity associated with status epilepticus, this topic has received little attention within the literature. A systematic approach to treatment should start with management of airway, breathing, and circulation, followed by administration of benzodiazepines and intravenous antiepileptic drugs, and rapid escalation of therapy to prevent morbidity and mortality. Armed with the information in this article, nurses will have a higher-level understanding of what to do when encountering a patient in status epilepticus.

A Literature Review Revisiting Phenytoin-Induced Sinus Arrest

Classically, phenytoin (PTN) infusion for the treatment of status epilepticus has been proven to be associated with cardiovascular toxicity, including dysrhythmias, hypotension, and cardiovascular collapse. Subsequently, fosphenytoin (FOS) was introduced on the market in 1997 with claims of having less cardiac toxicity. However, since then, many accounts of cardiac events have been reported undermining these claims. FOS gained popularity due to its water solubility, which allows 3 times faster infusion in comparison with PTN with less venous irritation and local toxicity. FOS is the phosphate ester prodrug of PTN and is rapidly converted to PTN independent of the dose and rate of administration. Intravenous FOS and PTN are bioequivalent. Adverse cardiac effects of both intravenous FOS and PTN have been correlated to the rate of infusion, concentration of the agent, known risk factors, or pre-existing hypersensitivity, and most cases have been identified after infusing a loading dose of these medications. This case report is unique, in that, the patient developed sinus arrest while concurrently receiving oral PTN and intravenous FOS. Clinicians should be more cognizant of the association of FOS and PTN with adverse cardiac events. Baseline electrocardiogram should be obtained on all patients prescribed FOS or PTN to identify underlying cardiac problems that may place the patient in a higher risk category. Telemetry should be performed on all patients receiving PTN in an inpatient setting.

Extracorporeal Treatment in Phenytoin Poisoning: Systematic Review and Recommendations from the EXTRIP (Extracorporeal Treatments in Poisoning) Workgroup

The Extracorporeal Treatments in Poisoning (EXTRIP) Workgroup conducted a systematic literature review using a standardized process to develop evidence-based recommendations on the use of extracorporeal treatment (ECTR) in patients with phenytoin poisoning. The authors reviewed all articles, extracted data, summarized findings, and proposed structured voting statements following a predetermined format. A 2-round modified Delphi method was used to reach a consensus on voting statements, and the RAND/UCLA Appropriateness Method was used to quantify disagreement. 51 articles met the inclusion criteria. Only case reports, case series, and pharmacokinetic studies were identified, yielding a very low quality of evidence. Clinical data from 31 patients and toxicokinetic grading from 46 patients were abstracted. The workgroup concluded that phenytoin is moderately dialyzable (level of evidence = C) despite its high protein binding and made the following recommendations. ECTR would be reasonable in select cases of severe phenytoin poisoning (neutral recommendation, 3D). ECTR is suggested if prolonged coma is present or expected (graded 2D) and it would be reasonable if prolonged incapacitating ataxia is present or expected (graded 3D). If ECTR is used, it should be discontinued when clinical improvement is apparent (graded 1D). The preferred ECTR modality in phenytoin poisoning is intermittent hemodialysis (graded 1D), but hemoperfusion is an acceptable alternative if hemodialysis is not available (graded 1D). In summary, phenytoin appears to be amenable to extracorporeal removal. However, because of the low incidence of irreversible tissue injury or death related to phenytoin poisoning and the relatively limited effect of ECTR on phenytoin removal, the workgroup proposed the use of ECTR only in very select patients with severe phenytoin poisoning.

Systemic complications of status epilepticus--An update

Systemic complications occur at every stage of status epilepticus, involve every organ system, and may worsen outcome. Initially, there is a massive catecholamine release and hyperadrenergic state that may result in neurocardiogenic, pulmonary, and, sometimes, musculoskeletal or renal injury. Further medical complications accompany the various treatments used to abort the seizures including the use of nonanesthetic antiseizure drugs and high-dose anesthetic infusions. Later, sequelae of prolonged immobility and critical illness occur and add to the cumulative morbidity of these patients. Clinicians should follow a protocol to guide screening for early markers of systemic injury, complications of specific pharmacologic and adjunctive treatments, and periodic surveillance for complications related to prolonged immobility. This article is part of a Special Issue entitled "Status Epilepticus".

Pediatric status epilepticus management

PURPOSE OF REVIEW

This review discusses the management of status epilepticus in children, including both anticonvulsant medications and overall management approaches.

RECENT FINDINGS

Rapid management of status epilepticus is associated with a greater likelihood of seizure termination and better outcomes, yet data indicate that there are often management delays. This review discusses an overall management approach aiming to simultaneously identify and manage underlying precipitant causes, administer anticonvulsants in rapid succession until seizures have terminated, and identify and manage systemic complications. An example management pathway is provided.

SUMMARY

Status epilepticus is a common neurologic emergency in children and requires rapid intervention. Having a predetermined status epilepticus management pathway can expedite management.

Therapeutic hypothermia decreases phenytoin elimination in children with traumatic brain injury

OBJECTIVE

Preclinical and clinical studies have suggested that therapeutic hypothermia, while decreasing neurologic injury, may also lead to drug toxicity that may limit its benefit. Cooling decreases cytochrome P450 (CYP)-mediated drug metabolism, and limited clinical data suggest that drug levels are elevated. Fosphenytoin is metabolized by cytochrome P450 2C, has a narrow therapeutic range, and is a commonly used antiepileptic medication. The objective of this study was to evaluate the impact of therapeutic hypothermia on phenytoin levels and pharmacokinetics in children with severe traumatic brain injury.

DESIGN

Pharmacokinetic analysis of subjects participating in a multicenter randomized phase III study of therapeutic hypothermia for severe traumatic brain injury.

SETTING

ICU at the Children's Hospital of Pittsburgh.

PATIENTS

Nineteen children with severe traumatic brain injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A sum of 121 total and 114 free phenytoin levels were evaluated retrospectively in 10 hypothermia-treated and nine normothermia-treated children who were randomized to 48 hours of cooling to 32-33°C followed by slow rewarming or controlled normothermia. Drug dosing, body temperatures, and demographics were collected during cooling, rewarming, and posttreatment periods (8 d). A trend toward elevated free phenytoin levels in the hypothermia group (p=0.051) to a median of 2.2 mg/L during rewarming was observed and was not explained by dosing differences. Nonlinear mixed-effects modeling incorporating both free and total levels demonstrated that therapeutic hypothermia specifically decreased the time-variant component of the maximum velocity of phenytoin metabolism (Vmax) 4.6-fold (11.6-2.53 mg/hr) and reduced the overall Vmax by ~50%. Simulations showed that the increased risk for drug toxicity extends many days beyond the end of the cooling period.

CONCLUSIONS

Therapeutic hypothermia significantly reduces phenytoin elimination in children with severe traumatic brain injury leading to increased drug levels for an extended period of time after cooling. Pharmacokinetic interactions between hypothermia and medications should be considered when caring for children receiving this therapy.

Medical treatment of pediatric status epilepticus

Status epilepticus (SE) is a common pediatric neurologic emergency that refers to a prolonged seizure or recurrent seizures without a return to baseline mental status between seizures. Appropriate treatment strategies are necessary to prevent prolonged SE and its associated morbidity and mortality. This review discusses the importance of a rapid and organized management approach, reviews data related to commonly utilized medications including benzodiazepines, phenytoin, phenobarbital, valproate sodium, and levetiracetam, and then provides a sample SE management algorithm.

Treatment of early and late kainic acid-induced status epilepticus with the noncompetitive AMPA receptor antagonist GYKI 52466

PURPOSE

Benzodiazepines such as diazepam may fail to effectively treat status epilepticus because benzodiazepine-sensitive GABA(A) receptors are progressively internalized with continued seizure activity. Ionotropic glutamate receptors, including AMPA receptors, are externalized, so that AMPA receptor antagonists, which are broad-spectrum anticonvulsants, could be more effective treatments for status epilepticus. We assessed the ability of the noncompetitive AMPA receptor antagonist GYKI 52466 to protect against kainic acid-induced status epilepticus in mice.

METHODS

Groups of animals treated with kainic acid received GYKI 52466 (50 mg/kg followed in 15 min by 50 mg/kg) or diazepam (25 mg/kg followed in 20 min by 12.5 mg/kg) beginning at 5 min of continuous seizure activity or 25 min later. The duration of seizure activity was determined by EEG recording from epidural cortical electrodes.

RESULTS

Both GYKI 52466 and diazepam rapidly terminated electrographic and behavioral seizures when administered early. However, diazepam-treated animals exhibited more seizure recurrences. With late administration, GYKI 52466 also rapidly terminated seizures and they seldom recurred, whereas diazepam was slow to produce seizure control and recurrences were common. Although both treatments caused sedation, GYKI 52466-treated animals retained neurological responsiveness whereas diazepam-treated animals did not. GYKI 52466 did not affect blood pressure whereas diazepam caused a sustained drop in mean arterial pressure.

DISCUSSION

Noncompetitive AMPA receptor antagonists represent a promising approach for early treatment of status epilepticus; they may also be effective at later times when there is refractoriness to benzodiazepines.

Blood pressure changes after intravenous fosphenytoin and levetiracetam in patients with acute cerebral symptoms

PURPOSE

To study the incidence and extent of the occasionally noted hypotension after intravenous (IV) infusions of fosphenytoin (FOS) and levetiracetam (LEV) in patients presenting with acute cerebral symptoms.

METHODS

Retrospective data collection of consecutive patients with acute cerebral symptoms who received IV infusions of a single dose of 750 mg or more of either fosphenytoin or levetiracetam and had documented blood pressure values in the 2h prior and the 2h after their IV infusion.

RESULTS

More than 10 mmHg drop in the systolic, diastolic and MBP was observed in the FOS group following the IV infusion (-16.82 mmHg, -11.60 mmHg, and 13.34 mmHg, respectively). However, there was not a significant change in the MBP after LEV infusion (1.54 mmHg, 1.84 mmHg, and 1.74 mmHg for systolic, diastolic and MBP change, respectively). The difference in the systolic, diastolic and MBP changes between the two groups was statistical significant (all p values are <0.0001) after adjusting for age, clinical presentations of the patients and if they were on any antihypertensive medication in the hospital. Sixty two percent of patients who received FOS had >10 mmHg decrease in their MBP. In the LEV group, only 2 of the 50 patients (4%) had >10 mmHg decrease in their MBP. The difference in proportion of the patients with >10 mmHg drop in MBP between the two study groups is also statistically significant (p<0.001) for age, clinical presentations of the patients and if they were on any antihypertensive medication in the hospital.

CONCLUSIONS

IV infusion of FOS in subjects presenting with acute cerebral symptoms may cause significant decreases in their blood pressure. This was not seen in patients receiving IV LEV infusions. Since maintaining adequate cerebral perfusion pressure is a key point in the management of patients with acute cerebral symptoms, the results of this study may carry a clinical impact on the management of this subgroup of patients.

Anticonvulsant medications in the pediatric emergency room and intensive care unit

Seizures are common in pediatric emergency care units, either as the main medical issue or in association with an additional neurological problem. Rapid treatment prolonged and repetitive seizures or status epilepticus is important. Multiple anti-convulsant medications are useful in this setting, and each has various indications and potential adverse effects that must be considered in regard to individual patients. This review discusses new data regarding anticonvulsants that are useful in these settings, including fosphenytoin, valproic acid, levetiracetam, and topiramate. A status epilepticus treatment algorithm is suggested, incorporating changes from traditional algorithms based on these new data. Treatment issues specific to complex medical patients, including patients with brain tumors, renal dysfunction, hepatic dysfunction, transplant, congenital heart disease, and anticoagulation, are also discussed.