Acute oral loading of carbamazepine-CR and phenytoin in a double-blind randomized study of patients at risk of seizures

Pharmacotherapy Overview of Seizure Management in the Adult Emergency Department

Seizures are a common cause of emergency department visits, and approximately 28% of epilepsy patients present to an emergency department annually for treatment. This article will provide an overview of the pharmacotherapeutic management of seizures and anticonvulsant therapy for patients who present to the adult emergency department, including practical information for pharmacists covering or cross-covering this practice area. The benzodiazepines are reviewed as a class, including dosing strategies, pharmacodynamic considerations, and advantages and disadvantages of lorazepam, diazepam, and midazolam. Indications for the use of phenytoin and fosphenytoin will be reviewed, as well as dosing, adverse effects, and cost-effectiveness data. In addition, dosing, administration, pharmacokinetics, and adverse effects of phenobarbital, carbamazepine, and valproate will be discussed. Clinical indications for serum anticonvulsant concentration monitoring and subsequent calculation of loading doses from serum concentrations are reviewed. Since status epilepticus is a life-threatening emergency, its therapeutic management is reviewed, including the use of continuous infusion midazolam, pentobarbital, and propofol. There are many opportunities for clinical pharmacists to collaborate with other members of the health care team to optimize efficacy and minimize adverse effects of anticonvulsant agents in the emergency department setting.

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.

Efficacy, tolerability, and pharmacokinetics of oxcarbazepine oral loading in patients with epilepsy

The rapid achievement of effective levels of antiepileptic drugs (AEDs) is required in patients with epilepsy who have a higher risk of seizures, and oral loading of AEDs may be an important consideration in these patients. We performed the present study to investigate the efficacy and tolerability of oral loading of oxcarbazepine in patients with recurrent seizures, or after temporary discontinuation of AEDs for diagnostic or presurgical evaluation of epilepsy. Forty adult patients were studied and oxcarbazepine was administered orally at a single loading dosage of 30 mg/kg. The plasma levels of oxcarbazepine and its active metabolite, 10,11-dihydro-10-hydroxy-carbazepine (monohydroxy derivative, MHD), were measured, and clinical assessment of adverse events was performed at 2, 4, 6, 8, 10, 12, 16, and 24 h after oral loading of oxcarbazepine. Approximately two-thirds of patients reached effective levels of MHD 2 h after receiving the oral loading, and all patients reached effective levels 4 h after oxcarbazepine administration. Most patients maintained therapeutic MHD levels for at least 16 h. Almost half of the patients experienced adverse events, but all were mild to moderate in severity and resolved spontaneously within 24 h. Our study shows that oral loading of oxcarbazepine is an effective and well-tolerated method for rapidly achieving therapeutic levels of MHD in patients with epilepsy, and is a useful option in selected patients with recurrent seizures, or after temporary discontinuation of AEDs.

Exploring efficacy and tolerability outcomes in patients with difficult-to-treat epilepsy receiving adjunctive topiramate at different titration rates--an exploratory study

OBJECTIVE

To compare rapid vs regular titration of topiramate concerning efficacy and safety.

MATERIALS AND METHODS

Open-label, prospective, single-center study exploring efficacy and tolerability of two adjunctive dosing regimens of topiramate (TPM) in adult patients with difficult-to-treat epilepsy. Based on investigator judgment, 21 of 50 consecutive patients received a rapid titration (starting dose 50 mg/day, stepwise increase with 50 mg/day after 3 days each until reaching the target dose), while the other 29 patients received titration according to the German prescribing information (starting dose 25 mg/day, stepwise increase with 25-50 mg/day every 7 days). Patients were observed until the target dose was reached and 3 months thereafter.

RESULTS

Mean final dosages were 136 mg/day (regular titration) and 213 mg/day (rapid titration). Efficacy and tolerability measures did not differ significantly. Forty-six percent of all patients experienced a seizure reduction of > or = 50%; 14% became seizure free. No serious adverse events occurred. The most common adverse effects were tiredness (20%), memory and language difficulties (18% each), slowness in thinking and speech (10%), psychomotor disturbance (8%) and paresthesia (8%).

CONCLUSIONS

This study suggests that rapid and conventional titration generate similar tolerability, safety and effectiveness in selected patients.

Rapid Oral Loading of Carbamazepine in the Emergency Department

STUDY OBJECTIVE

This study evaluates the safety and efficacy of rapid oral loading of carbamazepine in the emergency department (ED).

METHODS

Adult patients receiving maintenance carbamazepine who presented with negligible levels received an oral load of carbamazepine suspension, with a dose of 8 mg/kg.

RESULTS

Forty-two oral loads among 36 patients were studied. Mean subject age was 36 years; 61% of the sample were male patients. The actual load administered ranged from 7.9 to 8.6 mg/kg. The mean 3-hour carbamazepine level (therapeutic 4 to 12 microg/mL) was 6.5 microg/mL (SD 2.0 microg/mL). Three patients had subtherapeutic levels after loading (successful loading rate 93%). Adverse effects occurred in 58% of patients, most commonly drowsiness (26%) and nausea (23%). Other adverse effects included dizziness, nystagmus, abdominal pain, vomiting, ataxia, and double vision. Two patients were treated for vomiting. All other adverse effects were mild and self-limited.

CONCLUSION

Rapid oral loading of carbamazepine in the ED in this cohort, although effective, was associated with a high rate of adverse effects. Given a sample size of 36, 95% confidence intervals suggest that the rate of serious adverse effects may be as high as 9.7% and that the rate of successful loading may be as low as 76.9%.

A comparison of phenytoin-loading techniques in the emergency department

OBJECTIVES

To compare the effectivenesses of three phenytoin-loading techniques.

METHODS

Patients with subtherapeutic phenytoin concentrations who presented within 48 hours of a seizure were randomized to receive either 20 mg/kg of oral phenytoin (PO), divided in maximum doses of 400 mg every two hours, 18 mg/kg of intravenous phenytoin (IVP) at an initial infusion rate of 50 mg/min, or 18 mg/kg (phenytoin equivalents) of intravenous fosphenytoin (IVF) at an initial infusion rate of 150 mg/min.

RESULTS

A total of 45 patients were enrolled: 16 in the PO group, 14 in the IVP group, and 15 in the IVF group. The times required to reach therapeutic drug concentrations were (mean +/- standard deviation [SD]) 5.62 +/- 0.28 hours, 0.24 +/- 0.3 hours, and 0.21 +/- 0.28 hours, respectively. A total of 17, 27, and 32 adverse drug events were observed in the PO, IVP, and IVF groups, respectively, with significantly fewer events in the PO group (p = 0.02, p = 0.01). No significant difference was found between the numbers of necessary adjustments to the infusions in the two IV groups. The average time to safe emergency department discharge was significantly shorter for the IV groups compared with the PO group (p < 0.001).

CONCLUSIONS

Oral loading has fewer adverse drug events than either IV loading method, but its use may be limited when therapeutic concentrations are required quickly. Although IVF loading is faster, from an adverse-drug event perspective, no advantage of IVF over IVP was apparent.

[A practical study of the efficacy of a delayed-action preparation of carbamazepine (Tegretol CR 400) in the treatment of patients with partial epilepsy ]

INTRODUCTION

Carbamazepine (CBZ) is the first choice antiepileptic drug in the treatment of partial seizures. Many clinical studies show high efficacy and good tolerance of CBZ in the majority of patients. However, poor water solubility and erratic absorption as well as autoinduction of its metabolism, cause wide and unpredictable fluctuations in CBZ serum concentration. In order to avoid these problems controlled-release formulations of CBZ (Tegretol CR 400) were developed.

PURPOSE

The aim of this study was to evaluate the efficacy, tolerance and practicality of the therapy of partial seizures in adults with controlled-release CBZ (Tegretol CR 400).

PATIENTS AND METHODS

Over a three-year period we conducted an open pragmatic study of controlled-release CBZ in the therapy of 141 adult patients with established diagnosis of localized related epilepsy. Patients with progressive brain or systemic disease were excluded. All patients had unacceptable seizure frequency and were divided into four groups: 1) 34 with newly-diagnosed epilepsy; 2) 42 with chronic epilepsy and no previous antiepileptic medication; 3) 27 with chronic epilepsy previously treated with conventional preparations of carbamazepine (CBZ); and 4) 38 with chronic epilepsy previously treated with other antiepileptic medications. Patients were switched to controlled-release CBZ and the dosage was slowly adjusted. Baseline evaluation included the analysis of efficacy, tolerance and practicality of the controlled-release CBZ therapy. Three categories of efficiency were defined: 1) successful (patients without seizures); 2) partially successful (patients with improvement of at least 50% in frequency and severity of seizures); and 3) unsuccessful therapy (same or worse than before controlled-release CBZ). Tolerance and practicity were evaluated through the analysis of side effects and frequency of daily doses, respectively. These variables were compared to the corresponding ones after a period of at least three months of full dosage controlled-release CBZ therapy.

RESULTS

In all four groups the therapy was successful in 76%, 52%, 30% and 29%, partially successful in 18%, 43%, 30% and 32%, and unsuccessful in 6%, S%, 40% and 39%, respectfully. Side effects occurred less frequently in all 4 groups during the therapy with controlled-release CBZ. We found reduced frequency of drug administration (once or twice daily) in 97.9% of our patients.

DISCUSSION

Due to its slow and irregular absorption, short half life, wide and unpredictable fluctuation in plasma levels CBZ has decreased ability to control seizures, with the appearance of the intermittent side-effects such as diplopia, ataxia, headache and dizziness. Controlled-release formulation of CBZ sustains stable absorption and reduces fluctuations in carbamazepine serum concentration. Steady serum levels permit to the majority of patients to tolerate a higher total daily dose by reducing peak-dependent side-effects and improve compliance as a result of less frequent daily doses (1 or 2).

CONCLUSION

In patients with partial seizures controlled-release vs. conventional carbamazepine had better efficiency, based on an excellent tolerance, favorable daily dosage and superior compliance.

Loading strategies in acute mania

Treatment of acute mania has been greatly influenced by loading strategies. Loading has potential benefits, including rapid symptom reduction in mania and a shortened length of stay. Disadvantages include an increased likelihood of adverse effects of the medications. Loading strategies for lithium, valproic acid (divalproex sodium), carbamazepine, oxcarbazepine, olanzapine, and haloperidol decanoate in the treatment of acute mania are discussed. Recent studies highlight this treatment option for selected patients. It is the unique properties of the medications that influence their use in loading. Issues in patient selection for loading strategies with each medication are also considered.

Antiepileptic drug withdrawal in patients with temporal lobe epilepsy undergoing presurgical video-EEG monitoring

PURPOSE

To investigate antiepileptic drug (AED) withdrawal during video-EEG monitoring in adult patients with temporal lobe epilepsy (TLE).

METHODS

Between 1995 and 1997, 102 consecutive patients with refractory TLE were admitted to the epilepsy monitoring unit for presurgical evaluation. Patients were monitored with ongoing AEDs being rapidly decreased and discontinued in 4-6 days. The monitoring was continued until sufficient numbers of seizures were recorded. Serum AED levels were checked at admission and after the first complex partial seizure (CPS).

RESULTS

In all, 89 patients had 429 CPSs (mean, 4.8 per patient), including 156 (36.4%) secondarily generalized. A mean of 153.8 h (16-451 h) was required for completing the monitoring in each patient. Forty-three (48.3%) patients experienced seizure clusters, and eight (9.0%) had generalized seizures that had never occurred or had been absent for years. However, none evolved to status epilepticus. Carbamazepine was the most commonly used AED in 71.9% of patients, followed by valproate and phenytoin. When the first CPS occurred, mean 77.2 h since the beginning of the monitoring, serum levels of these three AEDs were mostly subtherapeutic rather than minimal.

CONCLUSIONS

Acute AED withdrawal effectively provoked seizures in TLE patients undergoing presurgical video-EEG monitoring. However, nearly 50% of patients had seizure clusters or secondarily generalized seizures. Serum AED levels were mostly subtherapeutic when the first CPS occurred.

Effects of phenytoin on cocaine self-administration in humans

The goal of this pilot study was to determine the effects of phenytoin on cocaine self-administration in a human laboratory model. Subjects were randomized to either phenytoin (n = 6) or placebo (n = 7). Those assigned to phenytoin treatment received a single oral loading dose of 20 mg/kg. The phenytoin and placebo treatment groups did not differ in the number of tokens valued at $5, exchanged for cocaine. Similarly, the cardiovascular and subjective response to cocaine administration did not show a statistically significant treatment effect. In this laboratory model, phenytoin did not alter either the self-administration or effects of cocaine.

Cognitive performances in newly referred patients with temporal lobe epilepsy: comparison with normal subjects in basal condition and after treatment with controlled-release carbamazepine

In order to verify whether the performance of patients with temporal lobe epilepsy (TLE) were different from those of the normal controls in various cognitive tasks, we conducted a neuropsychological study in the two groups, excluding the presence of other confounding factors in the group of TLE patients (newly referred, previously untreated, without cerebral lesions at neuroimaging, with low recurrence of seizures). In basal condition, no significant difference was found between the nine healthy controls and the eight TLE patients. The second aim of the study was to investigate the effect of the first administration of 400 mg controlled-release carbamazepine (CBZ-CR). The drug caused a significant decrease in verbal memory (short and long-term) in TLE patients, whereas, in the control group, the first administration of CBZ-CR caused only a less significant impairment of long-term verbal-memory. Finally, the cognitive effects of CBZ-CR were assessed after one month of therapy, only in the group of patients. Our data suggest that: 1) differences between patients and controls in basal conditions are not relevant, once the influence of seizures, of treatment and of anatomical lesions has been ruled out. In other words, our patients did not perform differently from controls simply because they had become epileptic 2) also in the controlled-release preparation, adverse effects of CBZ on cognitive function are minimal and limited to the beginning of treatment.