Pharmacoeconomic considerations in treatment options for acute seizures

Cost-effectiveness of nonemergency use of phenytoin

Parenteral phenytoin is an effective agent used to manage seizures, but it is associated with adverse effects and must be given intravenously. Fosphenytoin is higher in drug cost, but is more soluble, better tolerated and can be infused at rates three times that of phenytoin. When infusion rate is not an issue the adverse effect risk becomes a focus of concern, as well as cost. The determination of the point at which the treatment costs of infusion-related adverse effects of phenytoin outweigh the drug costs of fosphenytoin has been attempted through various clinical economic analyses. Strategies developed to promote the safe use of intravenous phenytoin are based on patient selection, recommended administration methods and patient monitoring. When rapid attainment of serum phenytoin levels is required or in patients at high risk of adverse effects secondary to parenteral phenytoin, fosphenytoin is clearly preferred. This review will focus on the implications of the use of parenteral phenytoin products in the nonemergent setting where potential adverse effects of parenteral phenytoin may be avoided with use of established criteria for patient selection and administration.

Comparative Efficacy and Safety of Antiepileptic Drugs for the Treatment of Status Epilepticus

Status epilepticus (SE) is a medical emergency with high mortality rate. Common causes of SE include noncompliance with antiepileptic medications, drug- and alcohol-related etiologies, and central nervous system (CNS) infections. Because prolonged seizures can cause neuronal damage, treatment should be initiated promptly to avoid potential complications. Previous studies support intravenous (IV) lorazepam as first-line therapy and IV phenytoin or fosphenytoin as a second-line medication. If first-and second-line medications fail to control SE, further treatment with propofol, pentobarbital, midazolam, or other medications should be considered. Many of the drugs currently used to control SE are associated with sedation, respiratory suppression, hypotension, cardiac dysrhythmia, and anaphylactic reactions. Therefore, IV valproate or other newer antiepileptic drugs may be considered as an alternative third-line therapy for those who cannot tolerate the hypotensive effects of other anticonvulsants. This paper reviews comparative effectiveness and safety concerns among frequently used medications for SE.

Cost-effectiveness of oral phenytoin, intravenous phenytoin, and intravenous fosphenytoin in the emergency department

STUDY OBJECTIVE

Oral phenytoin, intravenous phenytoin, and intravenous fosphenytoin are all commonly used for loading phenytoin in the emergency department (ED). The cost-effectiveness of each was compared for patients presenting with seizures and subtherapeutic phenytoin concentrations.

METHODS

A simple decision tree was developed to determine the treatment costs associated with each of 3 loading techniques. We determined effectiveness by comparing adverse event rates and by calculating the time to safe ED discharge. Time to safe ED discharge was defined as the time at which therapeutic concentrations of phenytoin (>or=10 mg/L) were achieved with an absence of any adverse events that precluded discharge. The comparative cost-effectiveness of alternatives to oral phenytoin was determined by combining net costs and number of adverse events, expressed as cost per adverse events avoided. Cost-effectiveness was also determined by comparing the net costs of each loading technique required to achieve the time to safe ED discharge, expressed as cost per hour of ED time saved. The outcomes and costs were primarily derived from a prospective, randomized controlled trial, augmented by time-motion studies and alternate-cost sources. Costs included the cost of drugs, supplies, and personnel. Analyses were also performed in scenarios incorporating labor costs and savings from using a lower-urgency area of the ED.

RESULTS

The mean number of adverse events per patient for oral phenytoin, intravenous phenytoin, and intravenous fosphenytoin was 1.06, 1.93, and 2.13, respectively. Mean time to safe ED discharge in the 3 groups was 6.4 hours, 1.7 hours, and 1.3 hours. Cost per patient was 2.83 dollars, 21.16 dollars, and 175.19 dollars, respectively, and did not differ substantially in the Labor and Triage (lower-urgency area of ED) scenarios. When the measure of effectiveness was adverse events, oral phenytoin dominated intravenous phenytoin and intravenous fosphenytoin, with a lower cost and number of adverse events. With time to safe ED discharge as the outcome measure, the incremental cost-effectiveness ratios were 3.90 dollars and 387.27 dollars per hour of ED time saved for oral phenytoin versus intravenous phenytoin and for intravenous fosphenytoin versus intravenous phenytoin, respectively.

CONCLUSION

Oral phenytoin is the most cost-effective loading method in most settings. Intravenous phenytoin is preferred if one is willing to pay an additional 20.65 dollars to 44.25 dollars per patient and willing to have more adverse events for a quicker average time to safe ED discharge. It is unlikely that intravenous fosphenytoin is justifiable in any setting.

Adverse events associated with intravenous phenytoin in children: a prospective study

A prospective study was undertaken to assess the type and frequency of adverse side-effects following the use of intravenous phenytoin in children. Twenty-two children received a total of 100 doses over a 10-month period. Six patients (27%) experienced one or more side-effects, including extravasation of the drug, hypotension and cardiac arrhythmia. No patient developed skin necrosis, including the 'purple glove syndrome'. Recovery from all adverse side-effects was spontaneous and complete. It is possible that some or all of these side-effects may have been caused by an excessive rate of infusion of phenytoin or the saline 'flush' following administration of the drug. The overall frequency of side-effects was perhaps less than expected.

New management strategies in the treatment of status epilepticus

Status epilepticus is a neurologic emergency associated with high mortality and long-term disability. Recent advances in our understanding of the pathophysiological mechanisms involved in the initiation and perpetuation of seizure activity have revealed that status epilepticus is a dynamic and evolving process. Alterations at the cellular level parallel physiological, physical, and electrical changes at the bedside. Loss of cerebral autoregulation and neuronal damage begin after 30 minutes of continuous seizure activity. This understanding has led to changes in treatments of status epilepticus, which must be multidisciplinary and occur simultaneously in many different areas. The goals of pharmacological therapy are to terminate seizures early and prevent recurrence. Two recent large clinical studies have shown the benefit of early administration of benzodiazepines to control status epilepticus. Pharmacological algorithms designed to focus medical management have trended toward earlier and more aggressive treatment. The hope is that continued exploration into the basic mechanisms involved in status epilepticus and future controlled clinical trials defining optimal medical management will produce further advances.

Status Epilepticus

Status epilepticus (SE) is a common neurologic emergency with a high mortality. Immediate recognition and rapid treatment are essential. After initial stabilization of airway and circulation, the patient should be treated as soon as possible with an intravenous (IV) benzodiazepine, followed immediately by IV fosphenytoin. If SE persists, general anesthesia should be initiated, with intubation and cardiac monitoring. Electroencephalogram must also be monitored to ensure suppression of all seizures. Etiology of SE should be assessed through history, examination, blood tests, and brain imaging.

Status epilepticus

Status epilepticus is a medical emergency that requires rapid and vigorous treatment to prevent neuronal damage and systemic complications. Failure to diagnose and treat status epilepticus accurately and effectively results in significant morbidity and mortality. Cerebral metabolic decompensation occurs after approximately 30 min of uncontrolled convulsive activity, and the window for treatment is therefore limited. Therapy should proceed simultaneously on four fronts: termination of seizures; prevention of seizure recurrence once status is controlled; management of precipitating causes of status epilepticus; management of the complications. This article reviews current opinions about the classification, aetiology and pathophysiology of adult generalised convulsive status epilepticus and details practical management strategies for treatment of this life-threatening condition.

Treatment of status epilepticus

The approach to treatment of status epilepticus has changed because of the demonstration of decreased mortality with rapid intervention, completion of a randomized, double-blind VA Cooperative study comparing first-line agents, and further understanding of the pathophysiologic changes discovered in experimental animal studies. This article reviews the treatments of generalized convulsive status epilepticus in the prehospital, emergency department, and intensive care unit settings.

Fosphenytoin and phenytoin in patients with status epilepticus: improved tolerability versus increased costs

Tonic-clonic status epilepticus (TCSE) is the most common neurological emergency and affects approximately 60000 patients each year in the US. The risk of complications increases substantially as TCSE lasts longer than 60 minutes. Ideally, drugs used to treat this condition should be well tolerated when administered as rapid intravenous infusions and should not interfere with patients' state of consciousness or cardiovascular and respiratory functions. Because of its efficacy, absence of sedation or respiratory suppression, intravenous phenytoin has largely replaced phenobarbital (phenobarbitone) as the second agent of choice (following the administration of a benzodiazepine) in the treatment of TCSE. While the efficacy of phenytoin in the treatment of acute seizures and TCSE is well established, the parenteral formulation of phenytoin has several inherent shortcomings which compromise its tolerability and limit the rate of administration. Intravenous phenytoin has been associated with fatal haemodynamic complications and serious reactions at the injection site including skin necrosis and amputation of extremities. Fosphenytoin, a phenytoin prodrug, has the same pharmacological properties as phenytoin but none of the injection site and cardiac rhythm complications of intravenous infusions of phenytoin. While fosphenytoin costs more than intravenous phenytoin, treating the acute and chronic complications of TCSE itself, and the complications of intravenous phenytoin can also be costly. All other factors being equal, there is no doubt that fosphenytoin is better tolerated and can be delivered faster than intravenous phenytoin; 2 measures that clearly improve outcome in patients with TCSE. The tolerability of intramuscular fosphenytoin also extends its use to clinical situations where prompt administration of a nondepressing anticonvulsant is indicated but secure intravenous access and cardiac monitoring are not available, such as treatment of seizures by rescue squads in the field and serial seizures in the institutionalised, elderly and other patients with intractable epilepsy.

Management approaches to prolonged seizures and status epilepticus

Status epilepticus (SE) treatment should proceed on four fronts: termination of SE, prevention of recurrence, management of potential precipitating causes, and management of SE complications and underlying conditions. The intensity of the treatment should reflect the risk to the patient from SE, and drugs likely to depress respiration and blood pressure should initially be avoided. The Veterans Administration cooperative trial showed that when treating overt SE, first-line treatment success rates were: lorazepam 64.9%; phenobarbital 58.2%; diazepam/phenytoin 55.8%; and phenytoin alone 43.6%. The aggregate response rate to second-line agents for patients who did not respond to first-line agents was 7.0%, and it was 2.3% for third-line agents, raising the question of the efficacy of a second and third drug. The recommended treatment for generalized convulsive SE is to begin with lorazepam. As a second-line agent, phenytoin or fosphenytoin, is still recommended if SE control is not achieved within 5 to 7 min. Fosphenytoin achieves a free phenytoin level of about 2 micro/mL in 15 min, as opposed to 25 min with phenytoin itself. Moreover, fosphenytoin is safer and, despite higher cost, it may be cost-effective. High-dose barbiturates, high-dose benzodiazepines, and propofol are employed for major treatment for refractory SE. Patients at this stage should undergo continuous electroencephalogram monitoring. Once SE is controlled, prevention of seizure recurrence should be individualized to each patient. The major complications of generalized convulsive SE (GCSE), rhabdomyolysis and hyperthermia, should be watched for and treated.