Comparison of Phenytoin and Fosphenytoin in Treatment of Active Seizures in the Emergency Department

Background and Objective

Ongoing seizure in the Emergency Department is a medical emergency and its aggressive management is essential. Prompt antiepileptic therapy with early cessation of seizure would minimize the morbidity and risk of recurrence. To compare time to seizure control with fosphenytoin to phenytoin protocol in the ED.

Materials and Methods

We conducted an observational study on patients with active seizure in the Emergency Department comparing phenytoin versus fosphenytoin protocol over one year.

Results

During the study period, we recruited 121 patients in the phenytoin group and 124 patients in the fosphenytoin group. Generalized tonic-clonic seizure (73.5% in phenytoin vs. 68.5% in fosphenytoin arm) was the most common type of seizure in both the arms. The mean time taken for cessation of seizure in the fosphenytoin arm (17.48 ± 49.24) was less than half of that in the phenytoin arm (37.20 ± 58.17) (mean difference: 19.72, P = 0.004, 95% CI: -33.27 to -6.17). There was a significant decrease in recurrence rates of seizure with phenytoin compared to the fosphenytoin arm (17.7% vs. 31.4%: OR: 0.47, P = 0.013; 95% CI: 0.26-0.86). Favorable STESS (≤2) was higher with phenytoin compared to fosphenytoin (60.3% vs. 48.4%). The overall in-hospital mortality rate in both arms was negligible (0.8%).

Conclusion

The mean time for cessation of active seizure with fosphenytoin was less than half that of phenytoin. Despite its higher cost and minor adverse effects when compared to phenytoin, benefits seem to outweigh its limitation.

Fosphenytoin dosing regimen including optimal timing for the measurement of serum phenytoin concentration in pediatric patients

INTRODUCTION

We aimed to evaluate the pediatric fosphenytoin dosing regimen, including optimal timing for the measurement of total serum phenytoin concentration (C_PHT).

METHODS

We retrospectively investigated pediatric patients with status epilepticus or seizure clusters treated with fosphenytoin between April 2013 and March 2018. Two C_PHT measurements were analyzed, one 2-4 h after the loading dose and another before the second dose. Individual pharmacokinetic parameters were estimated using the Bayesian method and were used to simulate C_PHT.

RESULTS

The present study involved 12 pediatric patients; the loading dose of fosphenytoin was 22.1 (17.2-27.2) mg/kg. The C_PHT was 13.4 (8.6-18.9) μg/mL 2-4 h after the loading dose. The C_PHT estimated from individual pharmacokinetic parameters 12 and 24 h after the loading dose was 9.5 (6.7-14.2) and 5.8 (3.7-10.0) μg/mL, respectively. If fosphenytoin was administered at a loading dose of 22.5 mg/kg and a maintenance dose of 5 or 7.5 mg/kg (administered every 12 h, starting 12 h after the loading dose), then the C_PHT on day 8 was estimated to be 5.74 (2.6-15.4) μg/mL at 5 mg/kg and 13.9 (5.7-31.0) μg/mL at 7.5 mg/kg.

CONCLUSIONS

In pediatric patients, a maintenance dose of fosphenytoin should be started 12 h after the loading dose, and a maintenance dose of 5-7.5 mg/kg/dose every 12 h may be better than every 24 h. We recommend measuring C_PHT at 2 and 12 h after the loading dose to simplify and safely adjust the dosage in clinical practice.

Treatment of Neonatal Seizures: Comparison of Treatment Pathways From 11 Neonatal Intensive Care Units

OBJECTIVE

Seizures are a common neonatal neurologic emergency. Many centers have developed pathways to optimize management. We evaluated neonatal seizure management pathways at level IV neonatal intensive care units (NICUs) in the United States to highlight areas of consensus and describe aspects of variability.

METHODS

We conducted a descriptive analysis of 11 neonatal seizure management pathways from level IV NICUs that specialize in neonatal neurocritical care including guidelines for electroencephalography (EEG) monitoring, antiseizure medication (ASM) choice, timing, and dose.

RESULTS

Study center NICUs had a median of 70 beds (interquartile range: 52-96). All sites had 24/7 conventional EEG initiation, monitoring, and review capability. Management pathways uniformly included prompt EEG confirmation of seizures. Most pathways included a provision for intravenous benzodiazepine administration if either EEG or loading of ASM was delayed. Phenobarbital 20 mg/kg IV was the first-line ASM in all pathways. Pathways included either fosphenytoin or levetiracetam as the second-line ASM with variable dosing. Third-line ASMs were most commonly fosphenytoin or levetiracetam, with alternatives including topiramate or lacosamide. All pathways provided escalation to continuous midazolam infusion with variable dosing for seizures refractory to initial medication trials. Three pathways also included lidocaine infusion. Nine pathways discussed ASM discontinuation after resolution of acute symptomatic seizures with variable timing.

CONCLUSIONS

Despite a paucity of data from controlled trials regarding optimal neonatal seizure management, there are areas of broad agreement among institutional pathways. Areas of substantial heterogeneity that require further research include optimal second-line ASM, dosage, and timing of ASM discontinuation.

Fosphenytoin alleviates herpes simplex virus infection-induced provoked and spontaneous pain-like behaviors in mice

In this study, we investigated the effects of fosphenytoin (fPHT) a water-soluble prodrug of phenytoin, on the pain responses of a mouse herpes zoster (HZ) pain model. Transdermal herpes simplex virus type 1 (HSV-1) inoculation induced mechanical allodynia and hyperalgesia of the hind paw and spontaneous pain-like behaviors, such as licking the affected skin. Intravenous injection of fPHT (15 and 30 mg/kg) alleviated HSV-1-induced provoked pain (allodynia and hyperalgesia). The suppressive effects of fPHT on provoked pain were weaker than those of diclofenac and pregabalin which were used as positive controls. fPHT, diclofenac, and pregabalin significantly suppressed HSV-1-induced spontaneous pain-like behaviors. Among them, high-dose fPHT (30 mg/kg) showed the strongest suppression. Intravenous fPHT may become a viable option for an acute HZ pain, especially for spontaneous pain.

Intravenous fosphenytoin therapy for rescue of acute trigeminal neuralgia crisis in patients awaiting neurosurgical procedures: A cross-sectional study

Few treatments exist for acute attacks of trigeminal neuralgia. Therefore, this study aimed to investigate the efficacy and safety of an intravenous fosphenytoin therapy protocol in a trigeminal neuralgia crisis. We conducted a single-center, retrospective, observational study of the records of 20 patients with trigeminal neuralgia who received intravenous fosphenytoin therapy (15 mg/mL in normal saline at 50 mg/min for 15 min, total 750 mg) during hospitalization between September 2015 and August 2020. Serum phenytoin concentration was measured 30 min post-infusion. Pain severity was evaluated using a numerical rating scale and was analyzed for statistical significance. The mean age of the patients was 67.5 years (female, 50.0%). The median numerical rating scale score (interquartile range) of pain severity was 2.35 (0-10), 0.65 (0-5), 0.15 (0-1), 2.00 (0-8), and 4.30 (0-10) at 15, 30, and 60 min, and 12 and 24 h, respectively (p < .001); the numerical rating scale score was 10 before treatment. Reduction in pain 24 h following treatment was significant. The mean phenytoin concentration was 12.8 μg/mL 30 min post-treatment. While mild dizziness occurred in four patients, all could walk independently within 60 min. The mean age and weight of patients with mild dizziness were significantly higher and lower, respectively (p < .001), than those of other patients. These results may provide physicians with new insights into the innovative therapeutic option of intravenous fosphenytoin and contribute to advancements in treating acute trigeminal neuralgia crisis.

Efficacy and safety of levetiracetam versus (fos)phenytoin for second-line treatment of epilepticus: a meta-analysis of latest randomized controlled trials

OBJECTIVES

To assess the efficiency and safety profiles of levetiracetam and (fos)phenytoin (phenytoin or fosphenytoin) for second-line treatment of seizures by performing a meta-analysis of RCTs.

METHODS

We systematically searched PubMed, Embase, Cochrane, FDA.gov, and ClinicalTrials.gov for RCTs (published before July 31, 2020; no language restrictions). Two independent reviewers screened abstracts and titles against inclusion and exclusion criteria published previously in the PROSPERO: CRD42020202736. Eleven studies fulfilled the established criteria. We assessed pooled data by using a random-effects model. Quality analysis was performed by using version 2 of the Cochrane risk-of-bias tool (RoB 2). RevMan v.5.3 was used to perform statistical analyses, and publication bias (egger's test) was assessed with Stata MP v.14.0.

RESULTS

Levetiracetam was similar to (fos)phenytoin in seizure termination rate (risk ratio [RR] 0.94; 95% CI 0.87 to 1.01), time of seizure termination (mean difference [MD] 0.44; -0.60 to 1.49), and drug resistance ([RR] 1.12, 0.86 to 1.45). The safety outcome showed a significant statistical difference between fosphenytoin group and levetiracetam group ([RR] 1.44, 1.14 to 1.81), while there was no significant difference observed between phenytoin treatment and levetiracetam treatment ([RR] 1.26, 0.99 to 1.60).

CONCLUSION

Levetiracetam was similar to (fos)phenytoin in cessation rate convulsive status epilepticus, and drug resistance, while it was superior (fos)phenytoin in pooled safety outcome. Further exploration is still needed as to whether it is the first choice for second-line drugs.

Levetiracetam versus fosphenytoin as a second-line treatment after diazepam for status epilepticus: study protocol for a multicenter non-inferiority designed randomized control trial

BACKGROUND

Status epilepticus (SE) is an emergency condition for which rapid and secured cessation is important. Phenytoin and fosphenytoin, the prodrug of phenytoin with less severe adverse effects, have been recommended as second-line treatments. However, fosphenytoin causes severe adverse events, such as hypotension and arrhythmia. Levetiracetam reportedly has similar efficacy and higher safety for SE; however, evidence to support its use for adult SE is lacking. In the present study, a non-inferiority designed multicenter randomized controlled trial (RCT) is being conducted to compare levetiracetam with fosphenytoin after diazepam as a second-line treatment for SE.

METHODS

This multicenter, prospective, and open-label RCT is conducted in emergency departments. Between December 23, 2019, and March 31, 2023, 176 patients with convulsive SE transported to an emergency room will be randomized into a fosphenytoin group and levetiracetam group at a ratio of 1:1. The definition of SE is "continuous seizures longer than 5 min or discrete seizures longer than 2 min with intervening consciousness disturbance." In both groups, diazepam is initially administered at 1-20 mg, followed by intravenous fosphenytoin at 22.5 mg/kg or intravenous levetiracetam at 1000-3000 mg. The primary outcome is the seizure cessation rate within 30 min. Seizure recurrence within 24 h, severe adverse events, and intubation rate within 24 h are secondary outcomes.

DISCUSSION

The present study was approved and conducted as an initiative study of the Japanese Association for Acute Medicine. If non-inferiority is identified, the society will pursue an application for the national health insurance coverage of levetiracetam for SE via a public knowledge-based application.

TRIAL REGISTRATION

Japan Registry of Clinical Trials jRCTs031190160 . Registered on December 13, 2019.

Intranasal fosphenytoin: The promise of phosphate esters in nose-to-brain delivery of poorly soluble drugs

Intranasal administration could increase both safety and efficacy of drugs acting on the central nervous system, but low solubility severely limits administration through this route. Phenytoin's prodrug, fosphenytoin, is hydrophilic and freely soluble in water, but less permeable since it is dianionic. We aimed to assess whether this phosphoester prodrug could be a suitable alternative to phenytoin in intranasal delivery. Secondly, we aimed to compare simple formulation strategies in fosphenytoin delivery. Fosphenytoin formulations containing thermosensitive and/or mucoadhesive (hydroxypropyl methylcellulose, HPMC) polymers were developed, guided by viscosity, gelling temperatures, osmolality, and in vitro drug release tests. Then, a pharmacokinetic study was performed, comparing an intravenous fosphenytoin solution, an intranasal fosphenytoin solution, and intranasal fosphenytoin mucoadhesive formulations with or without albumin. Formulations containing HPMC allowed high drug strengths, and had a relatively fast release profile, which was not changed by albumin. Intranasal administration of a formulation with HPMC and albumin prolonged drug concentration over time and led to complete or even increased absolute bioavailability. Moreover, phenytoin's blood levels did not reach the high peak obtained with intravenous administration. In conclusion, the use of phosphate ester prodrugs could be an efficient and safe strategy to increase the intranasal bioavailability of poorly soluble drugs.

Clinical Effectiveness of Levetiracetam Compared to Fosphenytoin in the Treatment of Benzodiazepine Refractory Convulsive Status Epilepticus

OBJECTIVES

To determine whether levetiracetam is an alternative to fosphenytoin to control Benzodiazepine Refractory Status Epilepticus (BRSE) in pediatric population and also to compare the acute drug related side-effects and ventilation requirement among the both arms of anti-epileptic drug therapy.

METHODS

All consecutive children admitted with BRSE were randomized to group A, who received fosphenytoin at 20 mg/kg phenytoin equivalents (PE) dose and group B who received levetiracetam at 40 mg/kg over 10 min. Time to terminate seizure (response latency) was measured. If seizure remained refractory after 20 min of test drug administration, appropriate drug escalation was made according to pediatrician's discretion. All primary and secondary outcome measures were compared between the two therapeutic groups.

RESULTS

Of 61 children enrolled over 18 mo period, 29 (47.5%) were randomized to group A and 32 (52.5%) were randomized to Group B. Baseline characteristics were comparable between the two groups. Among 61 children, 58(98%) required Pediatric Intensive Care Unit (PICU) admission and among those 5(8.2%) children required mechanical ventilation. Duration of PICU stay, hospital stay, the response latency and seizure recurrence were compared between both groups. Significant number of children received additional anti-epileptic drugs (AEDs) in fosphenytoin group [9/29(31%)] compared to levetiracetam group [2/32(7%)] to control seizure.

CONCLUSIONS

Levetiracetam may be an effective alternative to fosphenytoin in management of BRSE in children but multicentric trials with large sample size are needed to substantiate this observation.

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.

Nanoemulsions and thermosensitive nanoemulgels of phenytoin and fosphenytoin for intranasal administration: Formulation development and in vitro characterization

Phenytoin is a low solubility anticonvulsant drug. It has, nonetheless, other possible therapeutic indications, such as neuropathic pain, including trigeminal neuralgia, or wound healing. Its use has decreased due to side effects, but nasal/intranasal administration could significantly increase drug safety and efficacy. The aim of this work was to develop and study nanoemulsions and thermosensitive nanoemulgels of phenytoin and fosphenytoin, in combination, for intranasal administration, with immediate and sustained release profiles. Nanoemulsions were prepared by adding the aqueous phase, containing gelling polymers in the case of nanoemulgels, to emulsion preconcentrates, followed, in the optimized procedure, by premix membrane emulsification. Formulation design and optimization was guided by drug strength, rheological behavior, osmolality, mean droplet size and polydispersity. Fosphenytoin interfered significantly with Carbopol but not with Pluronic's gelation, and allowed to achieve drug strengths equivalent to 22 or 27 mg/g of phenytoin in lead nanoemulsions, and 16.7 mg/g of phenytoin in the lead nanoemulgel. The final selected low viscosity nanoemulsions had an immediate or prolonged fosphenytoin release profile, depending of anhydrous phase proportion (10% or 40%, respectively). The thermosensitive nanoemulgel, with 10% anhydrous phase, showed prolonged drug release. Future studies will establish whether they are more suited for topical effects or therapeutic brain delivery.

continuous midazolam for pediatric febrile status epilepticus

BACKGROUND

Fosphenytoin (fPHT) and continuous intravenous midazolam (cMDL) had commonly been used as second-line treatments for pediatric status epilepticus (SE) in Japan. However, there is no comparative study of these two treatments.

METHODS

We included consecutive children who 1) were admitted to Kobe Children's Hospital because of convulsion with fever and 2) were treated with either fPHT or cMDL as second-line treatment for convulsive SE lasting for longer than 30 min. We compared, between the fPHT and cMDL groups, the proportion of barbiturate coma therapy (BCT), incomplete recovery of consciousness, mechanical ventilation, and inotropic agents.

RESULTS

The proportion of BCT was not significantly different between the two groups (48.7% [20/41] in fPHT and 35.3% [29/82] in cMDL, p = 0.17). The prevalence of incomplete recovery of consciousness, mechanical ventilation, and inotropic agents was not different between the two groups. After excluding 49 patients treated with BCT, incomplete recovery of consciousness 6 h and 12 h after onset was more frequent in the cMDL group than in the fPHT group (71.7% vs. 33.3%, p < 0.01; 56.6% vs. 14.2%, p < 0.01; respectively). Mechanical ventilation was more frequent in the cMDL group than in the fPHT group (32.0% vs. 4.7%, p = 0.01).

CONCLUSIONS

Our results suggest that 1) the efficacy of fPHT and cMDL is similar, although cMDL may prevent the need for BCT compared with fPHT, and 2) fPHT is relatively safe as a second-line treatment for pediatric SE in patients who do not require BCT.

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.

Evaluation of phenytoin serum levels following a loading dose in the acute hospital setting

PURPOSE

Due to the complex pharmacokinetic profiles of phenytoin (PHT) and fosphenytoin (FOS), achieving sustained, targeted serum PHT levels in the first day of use is challenging.

METHODS

A population based approach was used to analyze total serum PHT (tPHT) level within 2-24h of PHT/FOS loading with or without supplementary maintenance or additional loading doses among PHT-naïve patients in the acute hospital setting. Adequate tPHT serum level was defined as ≥20μg/mL.

RESULTS

Among 494 patients with 545 tPHT serum levels obtained in the first 2-24h after the loading dose (LD), tPHT serum levels of either

CONCLUSION

Close laboratory surveillance and PHT/FOS dose adjustments are recommended to ensure adequate and sustained tPHT serum levels early in treatment. Free serum PHT level is the preferred method of drug monitoring.

Collapse

Key Words

• Fosphenytoin
• Serum phenytoin level
• Status epilepticus

Collapse

MESH Headings

• Adolescent
• Adult
• Aged
• Aged, 80 and over
• Anticonvulsants/blood
• Anticonvulsants/therapeutic use
• Child
• Community Health Planning
• Epilepsy/blood
• Epilepsy/drug therapy
• Female
• Humans
• Male
• Middle Aged
• Phenytoin/blood
• Phenytoin/therapeutic use
• Retrospective Studies
• Statistics as Topic
• Young Adult

Collapse

Grants

• T32 ES007271 NIEHS NIH HHS
• TL1 TR002000 NCATS NIH HHS
• UL1 TR000042 NCATS NIH HHS
• UL1 TR002001 NCATS NIH HHS

Collapse

Affiliation(s)

Olga Selioutski Department of Neurology, Strong Epilepsy Center, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA.
Katherine Grzesik Department of Biostatistics, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
Olga N Vasilyeva Department of Pharmacy, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
Ágúst Hilmarsson Landspitali University Hospital, Slettuvegi, Reykjavik, Iceland
A James Fessler Department of Neurology, Strong Epilepsy Center, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
Lynn Liu Department of Neurology, Strong Epilepsy Center, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
Robert A Gross Department of Neurology, Strong Epilepsy Center, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA

Collapse

Fosphenytoin-induced purple glove syndrome: A case report

BACKGROUND

Purple glove syndrome (PGS) is a poorly understood severe adverse drug reaction that is typically associated with intravenous phenytoin administration. Although fosphenytoin is thought to circumvent this risk of PGS, we reveal a rare case of PGS in a patient treated with fosphenytoin therapy.

CASE SUMMARY

A 71-year-old male with history of epilepsy was admitted for seizures and traumatic brain injury and intravenous fosphenytoin and levetiracetam were initiated. The patient continued to have seizure activity on continuous electroencephalography for which fosphenytoin dosing was increased with subsequent seizure control. Serum phenytoin levels became elevated with a total level reaching as high as 25.8ug/mL. Three days into fosphenytoin therapy he developed PGS in both hands. Causation was assessed with the Naranjo adverse drug reaction algorithm that suggested fosphenytoin was probably the cause of PGS. Ten days after discontinuing the fosphenytoin and administering a 7-day course of methylprednisolone, the purple glove syndrome completely resolved.

CONCLUSION

Early recognition and emergent management of PGS are key for optimal recovery. Although fosphenytoin has a significantly reduced risk of associated PGS compared to phenyotin, increased awareness for fosphenytoin-induce PGS can accelerate intervention and minimize morbidity of this rare yet detrimental adverse reaction.

Purple Glove Syndrome after Phenytoin or Fosphenytoin Administration: Review of Reported Cases and Recommendations for Prevention

The aim of our study was to identify all previously reported cases of phenytoin- or fosphenytoin-associated purple glove syndrome (PGS) and summarize the most current understanding of the pathophysiology, clinical presentation, diagnosis, and treatment of the disease. We searched the English language references from MEDLINE, EMBASE, CINAHL, TOXNET, and gray literature that featured one or more case descriptions of phenytoin- or fosphenytoin-associated PGS after administration and provided information on the clinical setting of the event and associated outcome(s). Descriptive statistics were employed to summarize relevant facts about the cases. We identified 82 unique cases of parenteral phenytoin-associated PGS and 5 cases of fosphenytoin-associated PGS that were published from 1984 to 2015. Additionally, we found two cases of PGS associated with oral formulation of phenytoin published from 1999 to 2015. The spectrum of tissue injury ranged from mild local cutaneous reactions around the infusion site to frank limb ischemia. Just over a half of cases reported symptoms after one dose of IV phenytoin. Pathologic findings included evidence for microvascular thrombosis and possible microvascular or subclinical extravasation as a contributing mechanism. Dopper ultrasound and conventional angiography were used in some patients to identify arterial or venous thrombosis. Various treatments were documented including the use of supportive care such as limb elevation and heat or cold application, utilization of systemic antibiotics, anticoagulants, or vasodilators, and local infiltration of hyaluronidase, heparin, or other compounds. In a small number of patients, invasive interventions such as regional anesthesia, thrombectomy, fasciotomy, and debridement were described. Time to resolution varied from days to weeks. Resolution of PGS without deficits was documented in the majority of cases. Skin changes followed by sensory and motor deficits were described in 16, 6, and 5 cases, respectively. Four patients underwent skin grafting and eight patients required limb amputation. Death as a result of PGS was documented in two patients. PGS associated with oral and injectable phenytoin or parenteral fosphenytoin has been documented in the literature and sometimes includes significant vascular thrombosis and potentially limb-threatening ischemia. Avoidance of small hand veins, adherence to recommended IV administration guidelines and monitoring of the infusion site for reactions should be considered to decrease the morbidity of IV phenytoin or fosphenytoin use. Patients with PGS and evidence of decreased distal perfusion should undergo prompt vascular imaging and potential intervention to avoid ischemic sequelae. Alternative anticonvulsant drugs should be considered in patients at risk for PGS when possible.

Development and application of an ex vivo fosphenytoin nasal bioconversion/permeability evaluation method

There is an increasing interest in the intranasal delivery of central nervous system-active drugs due to the existence of a direct nose-to-brain connection. However, poor solubility limits the amount of drug that can be administered within an aqueous solution. In the present work, the objectives were to develop an ex vivo bioconversion/permeability evaluation method and to study the ex vivo bioconversion of the hydrophilic phosphate ester prodrug fosphenytoin (FOS) to the active drug phenytoin (PHT) and their comparative nasal permeation. Bioconversion/permeability studies were performed in excised porcine nasal mucosa mounted in Ussing chambers. The physical integrity of the tissues was evaluated by measurement of the transepithelial electrical resistance (TEER). The simultaneous quantitative assay of FOS, PHT and its major metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) was developed and validated according to international guidelines using a liquid chromatography analytical method. The FOS bioconversion rate and PHT and FOS apparent permeability coefficients (Papp) were determined at different time points. FOS bioconversion was also qualitatively investigated in human nasal mucus. The developed liquid chromatography method combines a fast and inexpensive sample preparation with inactivation of the enzymatic metabolism of the prodrug during sample manipulation and storage. It was linear, precise, accurate, and presented a high analyte recovery. FOS was converted ex vivo to PHT but the metabolite HPPH was not detected. The bioconversion rate increased with FOS concentration and with time, which suggests a diffusion-limited process. FOS was also converted to its active drug by human nasal mucus. A novel mathematical data analysis method was developed to reduce the bias introduced by variable mucosal TEER in the permeability results. At comparable FOS and PHT concentrations the ln(Papp(PHT)) of both compounds showed little difference, which indicates that the use of a hydrophilic and charged prodrug did not hinder overall drug permeation. At the highest tested FOS concentration it was possible to quantify FOS in the receiver chambers, meaning that at a sufficiently high concentration the FOS permeation rate overcame its bioconversion rate. The ln(Papp(PHT)) tended to similar equilibrium values as the assay progressed, but with higher FOS concentrations that equilibrium was attained faster. Acidic pH reduced the permeability of both PHT and FOS. The developed bioconversion/permeability evaluation method will constitute an important tool to select the most promising formulations before proceeding to in vivo studies. Importantly, it allowed the demonstration of phosphatase activity and FOS bioconversion in nasal mucosa, as well as the prodrug's nasal permeation potential. Furthermore, this study demonstrates the possibility of formulating phosphate prodrugs of poorly soluble central nervous system-active drugs as a strategy to increase the solubilized drug doses administered through the nasal route.

Efficacy and safety of fosphenytoin for benign convulsions with mild gastroenteritis

OBJECTIVE

To clarify the efficacy and safety of fosphenytoin for seizures in children with benign convulsions and mild gastroenteritis.

METHODS

Using the mailing list of the Annual Zao Conference on Pediatric Neurology, we recruited patients who met the following criteria: (1) clinical diagnosis of benign convulsions with mild gastroenteritis and (2) treatment with intravenous fosphenytoin. Benign convulsions with mild gastroenteritis were defined as a condition of (a) seizures associated with gastroenteritis without electrolyte imbalance, hypoglycemia, or dehydration in patients (b) between 6 months and 3 years of age with (c) no preexisting neurological disorders, (d) no impaired consciousness, and (e) a body temperature less than 38.0 °C before and after the seizures. The efficacy of fosphenytoin was categorized as effective when cessation of seizures was achieved.

RESULTS

Data from 16 child patients were obtained (median age, 20 months). Seizures were completely controlled after the initial dose of fosphenytoin in 14 of 16 patients. The median loading dose of fosphenytoin was 22.5 mg/kg. In 10 patients, fosphenytoin was administered after other antiepileptic drugs such as diazepam and midazolam were used. Adverse effects of fosphenytoin, excessive sedation, or intravenous fluid incompatibility were not observed in any patients.

CONCLUSION

Fosphenytoin is effective and well tolerated among children with benign convulsions with mild gastroenteritis.

Lacosamide in status epilepticus: Update on the TRENdS study

Many patients with critical illness have been noted to have nonconvulsive seizures (NCSs) and nonconvulsive status epilepticus (NCSE). How aggressively these seizures should be treated is unclear. Many investigators feel that the morbidity of NCSs and NCSE is different from that of generalized convulsive status epilepticus (GCSE), so treatment should be less urgent. Consequently, many nonsedating AEDs have been used to treat NCSs and NCSE in patients with critical illness. Randomized, controlled trials demonstrating the efficacy of AEDs in NCSs and NCSE are lacking. The Treatment of Recurrent Electrographic Nonconvulsive Seizures (TRENdS) study compared lacosamide to fosphenytoin in the treatment of NCSs. An update of the study is presented. This article is part of a Special Issue entitled "Status Epilepticus".

Efficacy and safety of fosphenytoin for acute encephalopathy in children

PURPOSE

To evaluate the efficacy and safety of fosphenytoin (fPHT) for the treatment of seizures in children with acute encephalopathy.

METHODS

Using responses from physicians on the Annual Zao Conference on Pediatric Neurology mailing list we chose patients who met the following criteria: clinical diagnosis of acute encephalopathy and use of intravenous fPHT for the treatment of seizures. We divided the patients into two groups: acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) and other encephalopathies. The efficacy of fPHT was considered effective when a cessation of seizures was achieved.

RESULTS

Data of 38 children were obtained (median age, 27 months). Eighteen children were categorized into the AESD group and 20 into the other encephalopathies group. fPHT was administered in 48 clinical events. The median loading dose of fPHT was 22.5 mg/kg and was effective in 34 of 48 (71%) events. The rate of events in which fPHT was effective did not differ according to the presence or absence of prior antiepileptic treatment, subtype of acute encephalopathy, or the type of seizures. One patient experienced apnea and oral dyskinesia as adverse effects of fPHT, whereas arrhythmia, hypotension, obvious reduction of consciousness, local irritation, phlebitis and purple grove syndrome were not observed in any patient.

CONCLUSION

fPHT is effective and well tolerated among children with acute encephalopathy.

The established status epilepticus trial 2013

Benzodiazepine-refractory status epilepticus (established status epilepticus, ESE) is a relatively common emergency condition with several widely used treatments. There are no controlled, randomized, blinded clinical trials to compare the efficacy and tolerability of currently available treatments for ESE. The ESE treatment trial is designed to determine the most effective and/or the least effective treatment of ESE among patients older than 2 years by comparing three arms: fosphenytoin (fPHT) levetiracetam (LVT), and valproic acid (VPA). This is a multicenter, randomized, double-blind, Bayesian adaptive, phase III comparative effectiveness trial. Up to 795 patients will be randomized initially 1:1:1, and response-adaptive randomization will occur after 300 patients have been recruited. Randomization will be stratified by three age groups, 2-18, 19-65, and 66 and older. The primary outcome measure is cessation of clinical seizure activity and improving mental status, without serious adverse effects or further intervention at 60 min after administration of study drug. Each subject will be followed until discharge or 30 days from enrollment. This trial will include interim analyses for early success and futility. This trial will be considered a success if the probability that a treatment is the most effective is >0.975 or the probability that a treatment is the least effective is >0.975 for any treatment. Proposed total sample size is 795, which provides 90% power to identify the most effective and/or the least effective treatment when one treatment arm has a true response rate of 65% and the true response rate is 50% in the other two arms.