Dosing and therapeutic monitoring of phenytoin in young adults after neurotrauma: are current practices relevant?

A Retrospective Case Series on Valproic Acid for Early Post-Traumatic Seizure Prophylaxis After Traumatic Brain Injury in Patients With Concomitant Agitation

Purpose: Early post-traumatic seizures occur within 7 days following a traumatic brain injury and may lead to additional brain damage and poor outcomes. Levetiracetam or phenytoin is often used for seizure prophylaxis in this patient population, but valproic acid may be an appropriate therapeutic alternative in patients with concomitant agitation. Evidence for the use of valproic acid for both early post-traumatic seizure prophylaxis and agitation is limited. The purpose of this study is to examine the safety and efficacy of valproic acid for both early post-traumatic seizure prophylaxis and agitation. Methods: This single-center, retrospective case series includes 18 patients who received valproic acid for both early post-traumatic seizure prophylaxis and agitation. Efficacy for early post-traumatic seizure prophylaxis is assessed by the incidence of seizures within 7 days of injury. Efficacy for agitation is assessed by changes in Riker Sedation-Agitation Scale scores during valproic acid therapy. The safety of valproic acid is defined by the incidence of selected adverse events. Results: Among 18 patients with traumatic brain injuries receiving valproic acid for both early post-traumatic seizures and agitation, one patient experienced a seizure during the period of prophylaxis and thrombocytopenia was the most common adverse event. Conclusion: In this small cohort of patients, valproic acid appears be a potential option to prevent early post-traumatic seizures in patients with traumatic brain injuries and concomitant agitation with minimal adverse effects. Randomized, controlled studies are needed to further investigate the role of valproic acid for this indication, including standards for dosing regimens, serum drug monitoring, and the relationship between valproic acid treatment and mortality.

Efficacy of levetiracetam compared with phenytoin in prevention of seizures in brain injured patients: A meta-analysis

BACKGROUND

Early and/or late onset in patients with brain injury (BI) is associated with a poorer prognosis, and phenytoin (PHT) is standard of care to prevent seizures. Levetiracetam (LEV), an alternative antiepileptic drug, is associated with less cognitive disruption. The purpose of this study was to evaluate the safety and efficacy of LEV in the prevention of brain traumatic seizures with the standard drug PHT.

METHODS

Search the publications on comparison the safety and efficacy of LEV against the standard agent PHT in prevention of traumatic seizures in BI to January 2018. After rigorous reviewing on quality, the data were extracted from eligible trials. All trials analyzed the summary hazard ratios of the endpoints of interest.

RESULTS

LEV was found not more effective than PHT in terms of overall seizure (odds ratio [OR] = 0.73; 95% confidence interval [CI] = 0.51-1.05; P = .09), and late seizure (OR = 0.64; 95% CI = 0.34-1.19; P = .16) occurrence. However, there is significant difference in terms of early seizure (OR = 0.63; 95% CI = 0.40-0.99; P = .04). Moreover, there were no significant differences in terms of mortality (OR = 0.67; 95% CI = 0.43-1.05; P = .08), or side effects (OR = 1.31; 95% CI = 0.80-2.15; P = .29) between groups.

CONCLUSION

The meta-analysis showed that LEV prevention of seizures was associated with early seizure rates that were lower than the PHT-prolonged course of treatment. There is no statistically significant difference in the efficacy and safety profile of PHT and LEV in cases of traumatic BI.

Levetiracetam Prophylaxis for Post-traumatic Brain Injury Seizures is Ineffective: A Propensity Score Analysis

INTRODUCTION

Early seizures after severe traumatic brain injury (TBI) have a reported incidence of up to 15 %. Prophylaxis for early seizures using 1 week of phenytoin is considered standard of care for seizure prevention. However, many centers have substituted the anticonvulsant levetiracetam without good data on the efficacy of this approach. Our hypothesis was that the treatment with levetiracetam is not effective in preventing early post-traumatic seizures.

METHODS

All trauma patients sustaining a TBI from January 2007 to December 2009 at an urban level-one trauma center were retrospectively analyzed. Seizures were identified from a prospectively gathered morbidity database and anticonvulsant use from the pharmacy database. Statistical comparisons were made by Chi square, t tests, and logistic regression modeling. Patients who received levetiracetam prophylaxis were matched 1:1 using propensity score matching with those who did not receive the drug.

RESULTS

5551 trauma patients suffered a TBI during the study period, with an overall seizure rate of 0.7 % (39/5551). Of the total population, 1795 were diagnosed with severe TBI (Head AIS score 3-5). Seizures were 25 times more likely in the severe TBI group than in the non-severe group [2.0 % (36/1795) vs. 0.08 % (3/3756); OR 25.6; 95 % CI 7.8-83.2; p < 0.0001]. Of the patients who had seizures after severe TBI, 25 % (9/36) received pharmacologic prophylaxis with levetiracetam, phenytoin, or fosphenytoin. In a matched cohort by propensity scores, no difference was seen in seizure rates between the levetiracetam group and no-prophylaxis group (1.9 vs. 3.4 %, p = 0.50).

CONCLUSIONS

In this propensity score-matched cohort analysis, levetiracetam prophylaxis was ineffective in preventing seizures as the rate of seizures was similar whether patients did or did not receive the drug. The incidence of post-traumatic seizures in severe TBI patients was only 2.0 % in this study; therefore we question the benefit of routine prophylactic anticonvulsant therapy in patients with TBI.

Treatment of Convulsive Status Epilepticus

OPINION STATEMENT

Convulsive status epilepticus (CSE) is a medical emergency with an associated high mortality and morbidity. It is defined as a convulsive seizure lasting more than 5 min or consecutive seizures without recovery of consciousness. Successful management of CSE depends on rapid administration of adequate doses of anti-epileptic drugs (AEDs). The exact choice of AED is less important than rapid treatment and early consideration of reversible etiologies. Current guidelines recommend the use of benzodiazepines (BNZ) as first-line treatment in CSE. Midazolam is effective and safe in the pre-hospital or home setting when administered intramuscularly (best evidence), buccally, or nasally (the latter two possibly faster acting than intramuscular (IM) but with lower levels of evidence). Regular use of home rescue medications such as nasal/buccal midazolam by patients and caregivers for prolonged seizures and seizure clusters may prevent SE, prevent emergency room visits, improve quality of life, and lower health care costs. Traditionally, phenytoin is the preferred second-line agent in treating CSE, but it is limited by hypotension, potential arrhythmias, allergies, drug interactions, and problems from extravasation. Intravenous valproate is an effective and safe alternative to phenytoin. Valproate is loaded intravenously rapidly and more safely than phenytoin, has broad-spectrum efficacy, and fewer acute side effects. Levetiracetam and lacosamide are well tolerated intravenous (IV) AEDs with fewer interactions, allergies, and contraindications, making them potentially attractive as second- or third-line agents in treating CSE. However, data are limited on their efficacy in CSE. Ketamine is probably effective in treating refractory CSE (RCSE), and may warrant earlier use; this requires further study. CSE should be treated aggressively and quickly, with confirmation of treatment success with epileptiform electroencephalographic (EEG), as a transition to non-convulsive status epilepticus is common. If the patient is not fully awake, EEG should be continued for at least 24 h. How aggressively to treat refractory non-convulsive SE (NCSE) or intermittent non-convulsive seizures is less clear and requires additional study. Refractory SE (RSE) usually requires anesthetic doses of anti-seizure medications. If an auto-immune or paraneoplastic etiology is suspected or no etiology can be identified (as with cryptogenic new onset refractory status epilepticus, known as NORSE), early treatment with immuno-modulatory agents is now recommended by many experts.

Use of antiepileptics for seizure prophylaxis after traumatic brain injury

PURPOSE

Antiepileptics used for seizure prophylaxis after traumatic brain injury (TBI) are reviewed.

SUMMARY

Of the 275,000 people who are hospitalized with TBI each year, approximately 5-7% experience a posttraumatic seizure (PTS). According to the latest guidelines issued by the Brain Trauma Foundation and the American Academy of Neurology (AAN) for the management of severe TBI, PTS prophylaxis is recommended only during the first seven days after TBI. Of the available antiepileptic drugs, phenytoin has been the most extensively studied for the prophylaxis of PTS. Phenobarbital, valproate, and carbamazepine have not been as extensively researched, and, given their adverse-effect profiles and pharmacodynamic properties, there is no advantage to using these agents over phenytoin. Levetiracetam has demonstrated comparable efficacy to phenytoin for PTS prophylaxis and is associated with fewer adverse effects and monitoring considerations; it may be a reasonable alternative to phenytoin. However, levetiracetam has been associated with an increased seizure tendency. The Brain Trauma Foundation recommends using phenytoin for early PTS prophylaxis. The guidelines also state that valproate has demonstrated similar efficacy to phenytoin but warn that its use may be associated with increased mortality.

CONCLUSION

The available literature supports the use of antiepileptics for early PTS prophylaxis during the first week after a TBI. Phenytoin has been extensively studied for this indication and is recommended by the AAN and Brain Trauma Foundation guidelines for early PTS prophylaxis. Levetiracetam has demonstrated comparable efficacy to phenytoin for early PTS prophylaxis and may be a reasonable alternative to consider in this patient population.

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.

Retrospective analysis of levetiracetam compared to phenytoin for seizure prophylaxis in adults with traumatic brain injury

BACKGROUND

Phenytoin is standard of care for seizure prophylaxis following traumatic brain injury (TBI). Levetiracetam, an alternative antiepileptic drug, is utilized for seizure prophylaxis despite limited data supporting its use.

OBJECTIVE

Our primary outcome was post-TBI seizure activity measured by electroencephalogram (EEG) for levetiracetam versus phenytoin. Secondary outcomes were length of intensive care unit (ICU) stay, requirement for additional antiepileptic drugs (AED), and drug and monitoring costs.

METHODS

A retrospective review was performed of patients admitted to neurosurgical or surgical trauma ICU. Adult patients with at least 1 day of EEG monitoring were included. Patients were excluded if they had history of epilepsy, prior TBI, less than 48 hours of AED therapy, or additional AED prior to EEG monitoring.

RESULTS

A total 90 patients met inclusion criteria, with 18 receiving levetiracetam and 72 receiving phenytoin. Prevalence of EEG-confirmed seizure activity was similar between the levetiracetam and phenytoin groups (28% vs 29%; P = .99). ICU length of stay (13 vs 18 days; P = .28), time to EEG-confirmed seizure activity (4 vs 6 days; P = .24), and duration of seizure prophylaxis (9 vs 14 days; P = .18) were also similar. The median daily cost of levetiracetam therapy was $43 compared to $55 for phenytoin therapy and monitoring (P = .08). When all anticonvulsant therapy and monitoring were included, costs were lower for the levetiracetam group ($45 vs $83; P = .02).

CONCLUSION

Levetiracetam may provide an alternative treatment option for seizure prevention in TBI patients in the ICU. Total antiepileptic drug and monitoring costs were lower for levetiracetam patients.

Review article: phenytoin use and efficacy in the ED

This article reviews the evidence regarding the use of phenytoin in adult and paediatric patients experiencing seizures in the ED in Australasia, including relevant pharmacokinetics, dosage, therapeutic drug monitoring and methods of administration. It summarizes current evidence regarding the use of phenytoin in a number of seizure types commonly seen in ED. A search of Medline, Embase and Cochrane was performed using appropriate keyword and MeSH headings. A loading dose of phenytoin should be given to phenytoin naïve patients for the emergency treatment of seizures; parenteral administration results in therapeutic concentration sooner than oral administration but is associated with more frequent and significant adverse effects. Diluting phenytoin is safe but there is limited evidence regarding adverse effects of diluted phenytoin; a filter is probably not needed. Free phenytoin concentrations correlate best with antiseizure efficacy. Phenytoin is used in the treatment of status epilepticus although evidence here is limited; it may also be given to prevent early post-traumatic seizures. It should not be given to treat or prevent eclamptic or alcohol-related seizures. There is insufficient evidence regarding its use in preventing febrile convulsions, treating or preventing seizures due to space occupying lesions or intracerebral haemorrhage and thrombosis. In conclusion, phenytoin is appropriate for treatment of some seizures seen in the ED; it is associated with significant adverse effects; trials are ongoing regarding the use of other anticonvulsants in the treatment of status epilepticus.