The relative effectiveness of five antiepileptic drugs in treatment of benzodiazepine-resistant convulsive status epilepticus: a meta-analysis of published studies

PURPOSE

Systematic evaluation of published evidence-base of the efficacy of five antiepileptic drugs - lacosamide, levetiracetam, valproate, phenytoin and phenobarbital - in convulsive benzodiazepine-resistant status epilepticus.

METHODS

Data sources included electronic databases, personal communication, and back tracing of references in pertinent studies. These were prospective and retrospective human studies presenting original data for participants with convulsive benzodiazepine-resistant status epilepticus. Interventions were intravenous lacosamide, levetiracetam, phenobarbital, phenytoin and valproate. Outcome measured is clinically detectable cessation of seizure activity. Level-of-evidence was assessed according to Oxford Centre of Evidence-Based Medicine and The Cochrane Collaboration's Tool for Assessment of Risk. Twenty seven studies (798 cases of convulsive status epilepticus) were identified and 22 included in a meta-analysis. Random-effects analysis of dichotomous outcome of a single group estimate (proportion), with inverse variance weighting, was implemented. Several sources of clinical and methodological heterogeneity were identified.

RESULTS

Efficacy of levetiracetam was 68.5% (95% CI: 56.2-78.7%), phenobarbital 73.6% (95% CI: 58.3-84.8%), phenytoin 50.2% (95% CI: 34.2-66.1%) and valproate 75.7% (95% CI: 63.7-84.8%). Lacosamide studies were excluded from the meta-analysis due to insufficient data.

CONCLUSION

Valproate, levetiracetam and phenobarbital can all be used as first line therapy in benzodiazepine-resistant status epilepticus. The evidence does not support the first-line use of phenytoin. There is not enough evidence to support the routine use of lacosamide. Randomized controlled trials are urgently needed.

Short-term effects of neuroactive pharmaceutical drugs on a fish species: biochemical and behavioural effects

The presence of pharmaceutical residues in the aquatic environment is receiving great attention since significant levels of contamination have been found, not only in sewage treatment plant effluents, but also in open waters. In our study, the toxicity of three anticonvulsant drugs commonly found in the environment (diazepam, carbamazepine, and phenytoin) was evaluated in Lepomis gibbosus (pumpkinseed sunfish). This study focused on oxidative stress parameters, namely: glutathione reductase (GRed), glutathione S-transferases (GSTs), catalase (CAT), and lipid peroxidation (thiobarbituric acid reactive substances, TBARS) in the hepatic, digestive, and gill tissues of exposed animals. Simultaneously, we assessed the effects of these drugs in terms of behavioural parameters, such as scototaxis and activity. Exposure to diazepam caused an increase in GST activities in the gills and an inhibition of GRed in the digestive tract, relative to control, suggesting an antioxidant response. It also caused fish to spend more time swimming and less time in a refuge area (black compartment of an aquarium). Exposure to carbamazepine caused an increase in GSTs and GRed activity in the digestive tract, which is not always consistent with the literature. A significant positive correlation was found between carbamazepine concentration and time spent in motion and a negative correlation with time spent in black compartment. Exposure to phenytoin was responsible for adaptive responses in the activities of CAT and GSTs (in the liver), but it did not elicit any behavioural alterations. Although all three drugs seemed to induce oxidative stress in some organs, peroxidative damage (measured as TBARS concentrations) was not found at the selected range of concentrations. Our results enlighten the need for more research on the ecological consequences of pharmaceuticals in the aquatic environment, especially drugs that interfere with the CNS and behaviour, because the net outcome of these effects may be difficult to predict.

Dual-drug delivery of Ag-chitosan nanoparticles and phenytoin via core-shell PVA/PCL electrospun nanofibers

Dual-drug delivery systems were constructed through coaxial techniques, which were convenient for the model drugs used the present work. This study aimed to fabricate core-shell electrospun nanofibrous membranes displaying simultaneous cell proliferation and antibacterial activity. For that purpose, phenytoin (Ph), a well-known proliferative agent, was loaded into a polycaprolactone (PCL) shell membrane, and as-prepared silver-chitosan nanoparticles (Ag-CS NPs), as biocidal agents, were embedded in a polyvinyl alcohol (PVA) core layer. The morphology, chemical composition, mechanical and thermal properties of the nanofibrous membranes were characterized by FESEM/STEM, FTIR and DSC. The coaxial PVA-Ag CS NPs/PCL-Ph nanofibers (NFs) showed more controlled Ph release than PVA/PCL-Ph NFs. There was notable improvement in the morphology, thermal, mechanical, antibacterial properties and cytobiocompatibility of the fibers upon incorporation of Ph and Ag-CS NPs. The proposed core-shell PVA/PCL NFs represent promising scaffolds for tissue regeneration and wound healing by the effective dual delivery of phenytoin and Ag-CS NPs.

Changing trends in the use of seizure prophylaxis after traumatic brain injury: a shift from phenytoin to levetiracetam

PURPOSE

Current guidelines for traumatic brain injury (TBI) recommend antiepileptic drugs (AEDs) for 7 days after injury to decrease posttraumatic seizure risk. Phenytoin decreases seizure risk 73% vs placebo during this time. Levetiracetam (LEV) is an alternative; however, no published data validate comparable efficacy. Our objective was to evaluate seizure incidence 7 days after TBI in patients treated with phenytoin (PHT) vs LEV and to characterize practice of AED selection.

METHODS

A retrospective observational study was conducted using a Trauma Registry (Collector Trauma Registry; Digital Innovation, Inc, Forrest Hill, Md) to evaluate patients with TBI. Patients with an initial Head/Neck Abbreviated Injury Scale score of 3 or higher and a Glasgow Coma Scale of 8 or less were included.

RESULTS

Of 109 patients, 89 received PHT, and 20, LEV. Two patients experienced posttraumatic seizure, 1 in each group. Sixty-eight patients survived to hospital discharge; 65% received prophylactic AED greater than 7 days. Ninety-eight percent of 81 patients admitted between 2000 and 2007 received PHT, whereas 64% of 28 patients admitted between 2008 and 2010 received LEV.

CONCLUSION

Only 2 patients experienced posttraumatic seizure after receiving AED, indicating low incidence. Most surviving to hospital discharge received AED prophylaxis greater than 7 days despite guideline recommendations. After approval of intravenous LEV, a trend favoring LEV was observed.

Levetiracetam versus phenytoin in management of status epilepticus

The purpose of this study was to compare safety and efficacy of intravenous (IV) levetiracetam (LEV) with IV phenytoin (PHT) in management of status epilepticus (SE). The second-line treatment of SE is limited to a few drugs available in an IV formulation such as PHT, fosphenytoin and valproate. The relative lack of serious side effects and favourable pharmacokinetics of LEV made it a promising option in management of SE. Randomized trials comparing relative efficacy of second-line agents are remarkably lacking. In this study, consecutive patients of SE (n=44) were randomized to receive either IV PHT (20mg/kg) or IV LEV (20mg/kg). The primary end point was successful clinical termination of seizure activity within 30min after the beginning of the drug infusion. Secondary end points included recurrence of seizures within 24 hours, drug related adverse effects, neurological outcome at discharge, need for ventilatory assistance, and mortality during hospitalization. Both LEV and PHT were equally effective with regard to primary and secondary outcome measures. PHT achieved control of SE in 15 (68.2%) patients compared to LEV in 13 (59.1%; p=0.53). Both the groups showed comparable results with respect to recurrence of seizures within 24 hours (p=0.34), outcome at discharge as assessed by functional independence measure (p=0.68), need of ventilatory assistance (p=0.47) and death (p=1). From this study it can be concluded that LEV may be an attractive and effective alternative to PHT in management of SE.

Efficacy of sodium channel blockers in SCN2A early infantile epileptic encephalopathy

BACKGROUND

Recent clinical evidence supports a targeted therapeutic approach for genetic epileptic encephalopathies based on the molecular dysfunction.

PATIENT DESCRIPTION

A 2-day-old male infant presented with epileptic encephalopathy characterized by burst-suppression EEG background and tonic-clonic migrating partial seizures. The condition was refractory to phenobarbital, pyridoxine, pyridoxal phosphate and levetiracetam, but a dramatic response to an intravenous loading dose of phenytoin was documented by video-EEG monitoring. Over weeks phenytoin was successfully switched to carbamazepine to prevent seizure relapses associated with difficulty in maintaining proper blood levels of phenytoin. Genetic analysis identified a novel de novo heterozygous mutation (c.[4633A>G]p.[Met1545Val]) in SCN2A. At two years and three months of age the patient is still seizure-free on carbamazepine, although a developmental delay is evident.

CONCLUSIONS

Sodium channel blockers represent the first-line treatment for confirmed or suspected SCN2A-related epileptic encephalopathies. In severe cases with compatible electro-clinical features we propose a treatment algorithm based on a test trial with high dose intravenous phenytoin followed in case of a positive response by carbamazepine, more suitable for long-term maintenance treatment. Because of their rarity, collaborative studies are needed to delineate shared therapeutic protocols for EIEE based on the electro-clinical features and the presumed underlying genetic substrate.

Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis: An Analysis of Triggers and Implications for Improving Prevention

BACKGROUND

Stevens-Johnson syndrome and toxic epidermal necrolysis are severe mucocutaneous adverse drug reactions characterized by extensive epidermal detachment. The mortality rates have been reported to vary between 1% and 5% for Stevens-Johnson syndrome and 25% and 35% for patients with toxic epidermal necrolysis. Studies have shown that early recognition and prompt withdrawal of the causative agent leads to increased patient survival.

METHODS

A retrospective chart review was conducted on 64 patients admitted to Vancouver General Hospital with a diagnosis of Stevens-Johnson syndrome or toxic epidermal necrolysis from 2001 to 2011. The aim of this study was to identify the medications most often implicated in triggering Stevens-Johnson syndrome and toxic epidermal necrolysis, as well as to delineate the timeline of identification and removal of these triggers.

RESULTS

A trigger was identified in 75% of cases. Allopurinol was the single most common offending agent (20% of cases). Anticonvulsants and antibiotics were common triggers. The offending agent was often removed at time of hospital admission/diagnosis but not at onset of symptoms. A history of prior culprit drug exposure with previous mucocutaneous adverse reaction was noted in 19% of cases with identified triggers. Asians and Native North Americans had a higher mortality than whites, and Asians more frequently had allopurinol as a trigger.

CONCLUSIONS

The onset and high mortality rate of Stevens-Johnson syndrome/toxic epidermal necrolysis may be related to unawareness of the early signs and symptoms of Stevens-Johnson syndrome and toxic epidermal necrolysis, the common drug triggers that cause it, and what investigations (human leukocyte antigen typing in Asians) can be done to prevent it.

Non-imidazole histamine H3 receptor ligands incorporating antiepileptic moieties

A small series of histamine H3 receptor (H3R) ligands (1-5) incorporating different antiepileptic structural motifs has been newly synthesized. All compounds exhibited moderate to high in vitro hH3R affinities up to a sub-nanomolar concentration range with pKi values in the range of 6.25-9.62 with varying preferences for this receptor subtype. The compounds (1-5) were further investigated in vivo on anticonvulsant effects against maximum electroshock (MES)-induced and pentylenetetrazole (PTZ)-kindled convulsions in rats having phenytoin (PHT) as the reference antiepileptic drug (AED). Surprisingly, animals pretreated with 1 mg/kg, i.p. of 5,5-diphenyl-3-(3-(piperidin-1-yl)propyl)imidazolidine-2,4-dione (4) were only moderately protected and no protection was observed for compounds 1-3 and 5 in three different doses (1 mg, 5 mg, and 10 mg/kg i.p.). Compound 4 (1 mg/kg, i.p.) failed to modify PTZ-kindled convulsion. However, a dose of 10 mg/kg significantly reduced convulsions in both models. In contrast, 5,5-diphenyl-3-(4-(3-(piperidin-1-yl)propoxy)benzyl)imidazolidine-2,4-dione (5) (1, 5, and 10 mg/kg, i.p.) showed proconvulsant effects in the MES model with further confirmation of these results in the PTZ model as no protection was observed against convulsion in the doses tested (1 and 10 mg/kg). In addition, compound 4 (10 mg/kg, i.p.) significantly prolonged myoclonic latency time and shortened total convulsion duration when compared to control, PHT or standard H3R inverse agonist/antagonist pitolisant (PIT). Our results showed that H3R pharmacophores could successfully be structurally combined to antiepileptic moieties, especially phenytoin partial structures, maintaining the H3R affinity. However, the new derivatives for multiple-target approaches in epilepsy models are complex and show that pharmacophore elements are not easily pharmacologically combinable.

Direct and indirect comparison meta-analysis of levetiracetam versus phenytoin or valproate for convulsive status epilepticus

AIM

The aim of this study was to conduct a meta-analysis of published studies to directly compare intravenous (IV) levetiracetam (LEV) with IV phenytoin (PHT) or IV valproate (VPA) as second-line treatment of status epilepticus (SE), to indirectly compare intravenous IV LEV with IV VPA using common reference-based indirect comparison meta-analysis, and to verify whether results of indirect comparisons are consistent with results of head-to-head randomized controlled trials (RCTs) directly comparing IV LEV with IV VPA.

METHODS

Random-effects Mantel-Haenszel meta-analyses to obtain odds ratios (ORs) for efficacy and safety of LEV versus VPA and LEV or VPA versus PHT were used. Adjusted indirect comparisons between LEV and VPA were used.

RESULTS

Two RCTs comparing LEV with PHT (144 episodes of SE) and 3 RCTs comparing VPA with PHT (227 episodes of SE) were included. Direct comparisons showed no difference in clinical seizure cessation, neither between VPA and PHT (OR: 1.07; 95% CI: 0.57 to 2.03) nor between LEV and PHT (OR: 1.18; 95% CI: 0.50 to 2.79). Indirect comparisons showed no difference between LEV and VPA for clinical seizure cessation (OR: 1.16; 95% CI: 0.45 to 2.97). Results of indirect comparisons are consistent with results of a recent RCT directly comparing LEV with VPA.

CONCLUSION

The absence of a statistically significant difference in direct and indirect comparisons is due to the lack of sufficient statistical power to detect a difference. Conducting a RCT that has not enough people to detect a clinically important difference or to estimate an effect with sufficient precision can be regarded a waste of time and resources and may raise several ethical concerns, especially in RCT on SE.

Medical management of status epilepticus: Emergency room to intensive care unit

In convulsive status epilepticus (SE), achieving seizure control within the first 1-2 hours after onset is a significant determinant of outcome. Treatment is also more likely to work and be cost effective the earlier it is given. Initial first aid measures should be accompanied by establishing intravenous access if possible and administering thiamine and glucose if required. Calling for help will support efficient management, and also the potential for video-recording the events. This can be done as a best interests investigation to inform later management, provided adequate steps to protect data are taken. There is high quality evidence supporting the use of benzodiazepines for initial treatment. Midazolam (buccal, intranasal or intramuscular) has the most evidence where there is no intravenous access, with the practical advantages of administration outweighing the slightly slower onset of action. Either lorazepam or diazepam are suitable IV agents. Speed of administration and adequate initial dosing are probably more important than choice of drug. Although only phenytoin (and its prodrug fosphenytoin) and phenobarbitone are licensed for established SE, a now considerable body of evidence and international consensus supports the utility of both levetiracetam and valproate as options in established status. Both also have the advantage of being well tolerated as maintenance treatment, and possibly a lower risk of serious adverse events. Two adequately powered randomized open studies in children have recently reported, supporting the use of levetiracetam as an alterantive to phenytoin. The results of a large double blind study also including valproate are also imminent, and together likely to change practice in benzodiazepine-resistant SE.

Phenytoin: 80 years young, from epilepsy to breast cancer, a remarkable molecule with multiple modes of action

In 1908 phenytoin (5,5-diphenylhydantoin) was first synthesized as a barbiturate derivative in Germany by professor Heinrich Biltz (1865-1943) and subsequently resynthesized by an American chemist of the pharmaceutical company Parke-Davis in 1923 in Detroit. Screening phenytoin did not reveal comparable sedative side effects as barbiturates and, thus, Parke-Davis discarded this compound as a useful drug. In 1936, phenytoin's anticonvulsive properties were identified via a new animal model for convulsive disorders, developed by Putnam and Merritt, who also evaluated its clinical value in a number of patients in the period 1937-1940. For many diseases, mechanism of action of phenytoin remains obscure. The voltage-gated sodium channel was and is generally regarded as the main target to explain phenytoin's activity as an anticonvulsant and an anti-arrhythmic drug. This target, however, does not explain many of the other clinical properties of phenytoin. We will explore a number of original articles on phenytoin published in its 80 years history and give extra attention to the various hypothesis and experiments done to elucidate its mechanisms of action. Phenytoin has been explored in over 100 different disorders; the last two promising indications tested in the clinic are breast cancer and optic neuritis. Most probably, there are multiple targets active for these various disorders, and the insight into which targets are relevant is still very incomplete. It is remarkable that many pharmacological studies tested one dose only, mostly 50 or 100 μM, doses which most probably are higher than the non-plasma bound phenytoin plasma levels obtained during treatment.

The SCN8A encephalopathy mutation p.Ile1327Val displays elevated sensitivity to the anticonvulsant phenytoin

OBJECTIVE

SCN8A encephalopathy (early infantile epileptic encephalopathy; EIEE13) is caused by gain-of-function mutations resulting in hyperactivity of the voltage-gated sodium channel Nav 1.6. The channel is concentrated at the axon initial segment (AIS) and is involved in establishing neuronal excitability. Clinical features of SCN8A encephalopathy include seizure onset between 0 and 18 months of age, intellectual disability, and developmental delay. Seizures are often refractory to treatment with standard antiepileptic drugs, and sudden unexpected death in epilepsy (SUDEP) has been reported in approximately 10% of patients. In a recent study, high doses of phenytoin were effective in four patients with SCN8A encephalopathy. In view of this observation, we have investigated the relationship between the functional effect of the SCN8A mutation p.Ile1327Val and its response to phenytoin.

METHODS

The mutation was introduced into the Scn8a cDNA by site-directed mutagenesis. Channel activity was characterized in transfected ND7/23 cells. The effects of phenytoin (100 μm) on mutant and wild-type (WT) channels were compared.

RESULTS

Channel activation parameters were shifted in a hyperpolarizing direction in the mutant channel, whereas inactivation parameters were shifted in a depolarizing direction, increasing Na channel window current. Macroscopic current decay was slowed in I1327V channels, indicating an impairment in the transition from open state to inactivated state. Channel deactivation was also delayed, allowing more channels to remain in the open state. Phenytoin (100 μm) resulted in hyperpolarized activation and inactivation curves as well as greater tonic block and use-dependent block of I1327V mutant channels relative to WT.

SIGNIFICANCE

SCN8A - I1327V is a gain-of-function mutation with altered features that are predicted to increase neuronal excitability and seizure susceptibility. Phenytoin is an effective inhibitor of the mutant channel and may be of use in treating patients with gain-of-function mutations of SCN8A.

Phenytoin - An anti-seizure drug: Overview of its chemistry, pharmacology and toxicology

Phenytoin is a long-standing, anti-seizure drug widely used in clinical practice. It has also been evaluated in the context of many other illnesses in addition to its original epilepsy indication. The narrow therapeutic index of phenytoin and its ubiquitous daily use pose a high risk of poisoning. This review article focuses on the chemistry, pharmacokinetics, and toxicology of phenytoin, with a special focus on its mutagenicity, carcinogenicity, and teratogenicity. The side effects on human health associated with phenytoin use are thoroughly described. In particular, DRESS syndrome and cerebellar atrophy are addressed. This review will help in further understanding the benefits phenytoin use in the treatment of epilepsy.

Cardiovascular adverse effects of phenytoin

Phenytoin is an established drug in the treatment of acute repetitive seizures and status epilepticus. One of its main advantages over benzodiazepines is the less sedative effect. However, the possibility of cardiovascular adverse effects with the intravenous use of phenytoin cause a reluctance to its usage, and this has lead to a search for safer anticonvulsant drugs. In this study, we aimed to review the studies which evaluated the safety of phenytoin with respect to cardiovascular adverse effects. The original clinical trials and case reports listed in PUBMED in English language between the years of 1946-2014 were evaluated. As the key words, "phenytoin, diphenylhydantoin, epilepsy, seizure, cardiac toxicity, asystole, arrhythmia, respiratory arrest, hypotension, death" were used. Thirty-two clinical trials and ten case reports were identified. In the case reports, a rapid infusion rate (>50 mg/min) of phenytoin appeared as the major cause of increased mortality. In contrast, no serious cardiovascular adverse effects leading to death were met in the clinical trials which applied the recommended infusion rate and dosages. An infusion rate of 50 mg/min was reported to be safe for young patients. For old patients and patients with a cardiovascular co-morbidity, a slower infusion rate was recommended with a careful follow-up of heart rhythm and blood pressure. No cardiovascular adverse effect was reported in oral phenytoin overdoses except one case with a very high serum phenytoin level and hypoalbuminemia. Phenytoin is an effective and well tolerated drug in the treatment of epilepsy. Intravenous phenytoin is safe when given at recommended infusion rates and doses.

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.

The impact of topical phenytoin loaded nanostructured lipid carriers in diabetic foot ulceration

OBJECTIVE

The aim of this study is to develop, and characterize nanostructured lipid carriers (NLCs) of phenytoin (PHT) in order to improve its entrapment efficiency and sustained release to improve the healing process.

METHODS

Twenty-seven patients with neuropathic diabetic foot ulceration (DFU) were enrolled in this study. Patients were comparable regarding size, grading of ulcer and control of diabetes with no major deformity. All patients were managed by weekly sharp debridement if indicated and offloaded with cast shoes. They were equally divided into three groups: PHT-NLC-hydrogel (0.5%w/v), phenytoin hydrogel (0.5%w/v) and blank hydrogel groups. Changes in wound area were monitored over 2 months.

RESULTS

Baseline wound area of PHT-NLC, PHT and blank hydrogels were 5.50 ± 3.66, 3.94 ± 1.86 and 5.36 ± 2.14 cm², respectively. Ulcers treated with PHT-NLC hydrogel showed smaller wound area compared to control groups (ρ < 0.05). The overall reduction in ulcer size were 95.82 ± 2.22% for PHT-NLC-hydrogel in comparison to 47.10 ± 4.23% and -34.91 ± 28.33% for PHT and blank-hydrogel (ρ < 0.001), respectively.

CONCLUSION

PHT-NLC hydrogel speeds up the healing process of the DFU without adverse effects when compared to the positive and negative control hydrogels. Moreover, the study can open a window for topical application of NLCs loaded with PHT in the treatment of numerous dermatological disorders that resist conventional treatment.

KEY MESSAGE

The delivery of drug molecules and their localization into the skin is the main purpose of the topical dosage forms. In this manuscript, the impact of topical phenytoin loaded nanostructured lipid carrier in improving wound healing in patients with neuropathic diabetic foot ulceration was investigated. Phenytoin loaded nanostructured lipid carrier dressing was found to be more effective than phenytoin hydrogel at the same concentration in healing of neuropathic diabetic foot ulcer.

Comparison of cubosomes and hexosomes for the delivery of phenytoin to the brain

The ability to formulate cubosomes and hexosomes with a single lipid by changing only the colloidal stabiliser presents a unique opportunity to directly compare the biological performance of these uniquely structured nanoparticles. This was explored here via the encapsulation and brain delivery of a model anti-seizure drug, phenytoin, in selachyl alcohol cubosomes and hexosomes. Nanoparticles were prepared with Pluronic® F127 or Tween 80® as the stabiliser and characterised. The internal nanostructure of nanoparticles shifted from hexosomes when using Pluronic® F127 as the stabiliser to cubosomes when using Tween 80® and was conserved following loading of phenytoin, with high encapsulation efficiencies (>97%) in both particle type. Cytotoxicity towards brain endothelial cells using the hCMEC/D3 line was comparable regardless of stabiliser type. Finally, in vivo brain delivery of phenytoin encapsulated in cubosomes and hexosomes after intravenous administration to rats was studied over a period of 60 min, showing cubosomes to be superior to hexosomes, both in terms of brain concentrations and brain to plasma ratio. While the role of stabiliser and/or internal nanostructure remains to be conclusively determined, this study is the first in vivo comparison of cubosomes and hexosomes for the delivery of a therapeutic drug molecule across the BBB and into the brain.

A companion to the preclinical common data elements for pharmacologic studies in animal models of seizures and epilepsy. A Report of the TASK3 Pharmacology Working Group of the ILAE/AES Joint Translational Task Force

Preclinical pharmacology studies in animal models of seizures and epilepsy have provided a platform to identify more than 20 antiseizure drugs in recent decades. To minimize variability in lab‐to‐lab studies and to harmonize approaches to data collection and reporting methodology in pharmacologic evaluations of the next generation of therapies, we present common data elements (CDEs), case report forms (CRFs), and this companion manuscript to help with the implementation of methods for studies in established preclinical seizure and epilepsy models in adult rodents. The development of and advocacy for CDEs in preclinical research has been encouraged previously by both clinical and preclinical groups. It is anticipated that adoption and implementation of these CDEs in preclinical studies may help standardize approaches to minimize variability and increase the reproducibility of preclinical studies. Moreover, they may provide a methodologic framework for pharmacology studies in atypical animal models or models in development, which may ultimately promote novel therapy development. In the present document, we refer selectively to animal models that have a long history of preclinical use, and in some cases, are clinically validated.

Tacrolimus Drug-Drug Interaction with Nirmatrelvir/Ritonavir (Paxlovid™) Managed with Phenytoin

INTRODUCTION

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 or COVID-19) pandemic has had a significant impact on communities and health systems. The Federal Drug Administration (FDA) authorized Pfizer's nirmatrelvir/ritonavir (Paxlovid™) through an EUA for the treatment of mild to moderate cases of COVID-19 at high risk for progression to severe disease. Patients with a history of transplant who test positive for COVID-19 are considered high risk because of their immunosuppression and are therefore candidates for nirmatrelvir/ritonavir.

CASE REPORT

This is a case of a 67-year-old female with a past medical history of orthotopic heart transplant who received tacrolimus as part of her immunosuppressive regimen. She originally presented with complaints of dyspnea and cough for several days in the setting of COVID-19. The patient was started on nirmatrelvir/ritonavir due to her high risk for progression to severe disease. Four days after starting nirmatrelvir/ritonavir, she presented to the ED for slowed speech, fatigue, weakness, and loss of appetite. Upon admission she was found to have a supratherapeutic tacrolimus level of 176.4 ng/mL and an acute kidney injury. In this case, phenytoin was used as a CYP3A4 inducer to quickly decrease the tacrolimus level to within therapeutic range.

CONCLUSION

This case highlights the strong and important drug-drug interaction between tacrolimus and nirmatrelvir/ritonavir leading to toxic levels of tacrolimus. It also demonstrates the utility and effectiveness of phenytoin as a "rescue" medication for tacrolimus toxicity.

Computer aided identification of sodium channel blockers in the clinical treatment of epilepsy using molecular docking tools

Phenytoin (PHT) and Carbamazepine (CBZ) are excellent sodium channel blockers administered in clinical treatment of epileptic seizures. However, the narrow therapeutic range and limited pharmacokinetics of these drugs have raised serious concerns in the proper management of epilepsy. To overcome this, the present study attempts to identify a candidate molecule with superior pharmacological profile than PHT and CBZ through In silico approaches. PHT and CBZ served as query small molecules for Tanimoto based similarity search with a threshold of 95% against PubChem database. Aided by MolDock algorithm, high affinity similar compound against each query was retrieved. PHT and CBZ and their respective similar were further tested for toxicity profiles, LC 50 values and biological activity. Compounds, NSC403438 and AGN-PC-0BPCBP respectively similar to PHT and CBZ demonstrated higher affinity to sodium channel protein than their respective leads. Of particular relevance, NSC403438 demonstrated highest binding affinity bestowed with least toxicity, better LC 50 values and optimal bioactivity. NSC403438 was further mapped for its structure based pharmacophoric features. In the study, we report NSC403438 as potential sodium channel blocker as a better candidate than PHT and CBZ which can be put forth for pharmacodynamic and pharmacokinetic studies.

ABBREVIATIONS

AEDs - Antiepileptic drugs, BLAST - Basic Local Alignment Search Tool, CBZ - Carbamazepine, GEFS+ - Generalized Epilepsy with Febrile Seizures Plus, GPCR - G Protein Coupled Receptor, Nav - Sodium channel with specific voltage conduction, PDB - Protein Data Bank, PHT - Phenytoin, PIR - Protein Information resources, SAVES - Structural Analysis and Verification Server, VGSC - Voltage-gated Sodium channels.

Emergency treatment with levetiracetam or phenytoin in status epilepticus in children-the EcLiPSE study: study protocol for a randomised controlled trial

Background

Convulsive status epilepticus (CSE) is the most common life-threatening neurological emergency in childhood. These children are also at risk of significant morbidity, with acute and chronic impact on the family and the health and social care systems. The current recommended first-choice, second-line treatment in children aged 6 months and above is intravenous phenytoin (fosphenytoin in the USA), although there is a lack of evidence for its use and it is associated with significant side effects. Emerging evidence suggests that intravenous levetiracetam may be effective as a second-line agent for CSE, and fewer adverse effects have been described. This trial therefore aims to determine whether intravenous phenytoin or levetiracetam is more effective, and safer, in treating childhood CSE.

Methods/design

This is a phase IV, multi-centre, parallel group, randomised controlled, open-label trial. Following treatment for CSE with first-line treatment, children with ongoing seizures are randomised to receive either phenytoin (20 mg/kg, maximum 2 g) or levetiracetam (40 mg/kg, maximum 2.5 g) intravenously. The primary outcome measure is the cessation of all visible signs of CSE as determined by the treating clinician. Secondary outcome measures include the need for further anti-seizure medications or rapid sequence induction for ongoing CSE, admission to critical care areas, and serious adverse reactions. Patients are recruited without prior consent, with deferred consent sought at an appropriate time for the family. The primary analysis will be by intention-to-treat. The primary outcome is a time to event outcome and a sample size of 140 participants in each group will have 80% power to detect an increase in CSE cessation rates from 60% to 75%. Our total sample size of 308 randomised and treated participants will allow for 10% loss to follow-up.

Discussion

This clinical trial will determine whether phenytoin or levetiracetam is more effective as an intravenous second-line agent for CSE, and provide evidence for management recommendations. In addition, this trial will also provide data on which of these therapies is safer in this setting.

Trial registration

ISRCTN identifier, ISRCTN22567894. Registered on 27 August 2015

EudraCT identifier, 2014-002188-13. Registered on 21 May 2014

NIHR HTA Grant: 12/127/134

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2010-8) contains supplementary material, which is available to authorized users.

Association of HLA genotypes with phenytoin induced severe cutaneous adverse drug reactions in Thai children

PURPOSE

Phenytoin (PHT) is a common causative drug for severe cutaneous adverse drug reactions (SCARs) in children. SCARs, including drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), are associated with a variation in HLA genotypes. Blood screening for specific HLA allele before PHT prescription would help in the reduction of the incidence of PHT induced SCARs. This study was to investigate the association between variations of HLA genotypes and PHT induced SCARs in Thai children.

METHODS

Cases were Thai children aged between 0-18 years diagnosed with SCARs from PHT. Control groups were Thai children of corresponding age who had taken PHT for a least 12 weeks without any hypersensitivity reaction and healthy population controls. Blood samples from both groups were collected for HLA genotyping using a reverse-sequence specific oligonucleotide (SSO) probes method. Carrier rates of HLA alleles were compared between 22 cases (17 DRESS and 5 SJS-TEN), 60 tolerant controls and 649 population controls.

RESULTS

Two HLA alleles includingHLA-B*51:01 and HLA-C*14:02 were significantly associated with PHT induced DRESS (OR 5.83; 95 % CI 1.36-25.00, p = 0.022 and OR 5.85; 95 % CI 1.16-29.35, p = 0.039). HLA-B*38:02 was significantly associated with PHT induced SJS-TEN (OR12.67; 95 % CI 1.50-106.89, p = 0.044). Haplotype analysis demonstrated the association of HLA haplotype A*11:01-B*51:01-C*14:02 and PHT induced DRESS compared to tolerant controls and the healthy population control group (OR 8.92; 95 % CI 1.47-54.02, p = 0.019, and OR 10.2; 95 % CI 3.04-34.21, p = 0.002). HLA haplotype B*38:02-C*07:01 in PHT induced SJS-TEN was significantly higher than those in tolerant controls and the healthy population control group (40 % vs 3.3 % vs 0.3 %; OR 19.33; 95 % CI 1.98-188.59, p = 0.027 and OR 215.67; 95 % CI 22.40-2076.04, p = 0.0003. HLA-B*15:02 was not associated with PHT induced SCARs.

SIGNIFICANCE

An association betweenHLA-B*51:01 and HLA-C*14:02 and PHT induced DRESS and HLA-B*38:02 and PHT induced SJS-TEN has been demonstrated in Thai children.

Differences between the measured and calculated free serum phenytoin concentrations in epileptic patients

PURPOSE

The pharmacokinetics of phenytoin is complicated by genetic and environmental differences. It is, therefore, important to monitor the serum concentrations in patients who receive phenytoin. Because most of the phenytoin in serum is bound to proteins, the level of serum albumin influences the amount of free phenytoin.

MATERIALS AND METHODS

We compared the measured and calculated free phenytoin levels in epileptic patients who were taking phenytoin monotherapy, using the Sheiner-Tozer equation. A total of 49 patients (30 men and 19 women; age range, 15 - 87 years) were included in the study and their trough serum phenytoin and albumin concentrations were analyzed.

RESULTS

The linear correlation between free and total phenytoin concentrations was moderate (r = 0.822, p < 0.001). The mean difference between measured and calculated free phenytoin was large (0.65 +/- 0.88 microg/mL; 95% confidence interval (CI), -1.11 to 2.41). After dividing the patients into groups by albumin concentration, hypoalbuminemic patients (< 3.5 g/dL) more often had a greater percent difference (> or = 20%) than observed in the normoalbuminemic (> or = 3.5 g/dL) group.

CONCLUSION

In hypoalbuminemic patients, the measurement of free phenytoin level is necessary to properly evaluate the phenytoin level than that calculated from total phenytoin level.

Incidence of delayed seizures, delayed cerebral ischemia and poor outcome with the use of levetiracetam versus phenytoin after aneurysmal subarachnoid hemorrhage

Current guidelines recommend against the use of phenytoin following aneurysmal subarachnoid hemorrhage (aSAH) but consider other anticonvulsants, such as levetiracetam, acceptable. Our objective was to evaluate the risk of poor functional outcomes, delayed cerebral ischemia (DCI) and delayed seizures in aSAH patients treated with levetiracetam versus phenytoin. Medical records of patients with aSAH admitted between 2005-2012 receiving anticonvulsant prophylaxis with phenytoin or levetiracetam for >72 hours were reviewed. The primary outcome measure was poor functional outcome, defined as modified Rankin Scale (mRS) score >3 at first recorded follow-up. Secondary outcomes measures included DCI and the incidence of delayed seizures. The association between the use of levetiracetam and phenytoin and the outcomes of interest was studied using logistic regression. Medical records of 564 aSAH patients were reviewed and 259 included in the analysis after application of inclusion/exclusion criteria. Phenytoin was used exclusively in 43 (17%), levetiracetam exclusively in 132 (51%) while 84 (32%) patients were switched from phenytoin to levetiracetam. Six (2%) patients had delayed seizures, 94 (36%) developed DCI and 63 (24%) had mRS score >3 at follow-up. On multivariate analysis, only modified Fisher grade and seizure before anticonvulsant administration were associated with DCI while age, Hunt-Hess grade and presence of intraparenchymal hematoma were associated with mRS score >3. Choice of anticonvulsant was not associated with any of the outcomes of interest. There was no difference in the rate of delayed seizures, DCI or poor functional outcome in patients receiving phenytoin versus levetiracetam after aSAH. The high rate of crossover from phenytoin suggests that levetiracetam may be better tolerated.

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.