The association of patient weight and dose of fosphenytoin, levetiracetam, and valproic acid with treatment success in status epilepticus

Clonazepam Loading Dose in Status Epilepticus: Is More Always Better?

BACKGROUND AND OBJECTIVES

Benzodiazepines are the first treatment line in status epilepticus (SE). Despite their well-established benefit, benzodiazepines are frequently underdosed with potential detrimental consequences. In some European countries, clonazepam (CLZ) is commonly used as the first line treatment. The aim of this study was to explore the correlation between CLZ loading doses and SE outcome.

METHODS

This study included a retrospective analysis of a prospective registry in Lausanne, Switzerland (CHUV Lausanne University Hospital), including all SE episodes treated between February 2016 and February 2021. Only adults (> 16 years old) were included with CLZ used as the first treatment line. Post-anoxic SE were excluded because of significant differences in physiopathology and prognosis. Patient characteristics, SE features, the validated SE severity score (STESS), and treatment characteristics were prospectively recorded. We considered loading doses of 0.015 mg/kg or higher (following commonly recommended loading doses) as high doses. We analyzed outcome in terms of number of treatment lines after the CLZ, proportion of refractory episodes, intubation for airways protection, intubation for SE treatment, and mortality. We performed univariable analyses to investigate the association between loading doses and clinical response. A multivariable stepwise backward binary logistic regression was applied for adjusting for potential confounders. Multivariable linear regression was similarly used to analyze CLZ dose as a continuous variable.

RESULTS

We collected 251 SE episodes in 225 adult patients. Median CLZ loading dose was 0.010 mg/kg. CLZ high doses were used in 21.9% of SE episodes (in 43.8% for > 80% of the high dose). Thirteen percent of patients with SE were intubated for airways control, while intubation was needed in 12.7% for SE treatment. High CLZ loading doses were independently associated with younger age (median 62 versus 68 years old, p = 0.002), lesser weight (65 kg versus 75 kg, p = 0.001) and more frequent intubation for airways protection (23% vs 11%, p = 0.013), but differing CLZ dose was not associated with any outcome parameter.

CONCLUSION

CLZ high doses were more frequently used for SE treatment in younger patients with healthy weight and were more often associated with intubation for airways protection, probably as an adverse event. Varying CLZ dose did not alter outcome in SE, raising the possibility that commonly recommended doses are above what is needed, at least in some patients. Our results suggest that CLZ doses in SE may be individualized depending on the clinical setting.

What have we learned from the RAMPART and ESETT randomized controlled trials?

Lessons learned from the Rapid Anticonvulsant Medication Prior to Arrival Trial (RAMPART) and Established Status Epilepticus Treatment Trial (ESETT) trials are considered in three ways. First, by asking about the questions the trials were primarily designed to answer, then about the context of the intervention and characteristics of the patients described in secondary analyses, and finally, about what was learned about how to conduct trials in this space. The talk concludes with suggestions and a vision for how to best conduct future trials investigating status epilepticus. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.

Valproate in status epilepticus: Correlation between loading dose, serum levels, and clinical response

Background and purpose

Intravenous valproate (VPA) is an established treatment of status epilepticus (SE), but optimal loading dose was not fully assessed. We aimed at analyzing the correlation between VPA loading dose and subsequent plasma levels with clinical response in SE.

Methods

This was a retrospective study in one referral center of all consecutive VPA‐naïve SE episodes treated with VPA between January 2013 and June 2019, in which total VPA trough plasma levels after intravenous loading dose were available. Response to VPA, defined as last antiseizure medication introduced before SE resolution (without the need for additional treatment), was correlated with VPA loading dose and trough level. Correlations were adjusted for other SE characteristics.

Results

Among 128 SE episodes, 53 (41%) responded to VPA. Median VPA loading dose was 25.2 mg/kg (range, 7–58 mg/kg). Loading doses and total plasma levels were not associated with the probability of response or mortality. Correcting for other possible confounders (number of previously tried treatment, demographics, SE severity) did not alter these findings. Only 3.8% of SE episodes that responded to VPA received >30 mg/kg.

Conclusions

A high loading dose (>30 mg/kg) is not associated with a greater response rate in patients with SE. Therefore, it seems to bring little benefit. If confirmed in further studies, a dosage of 25–30 mg/kg appears adequate in SE.

A pharmacokinetic simulation study to assess the performance of a sparse blood sampling approach to quantify early drug exposure

Estimating early exposure of drugs used for the treatment of emergent conditions is challenging because blood sampling to measure concentrations is difficult. The objective of this work was to evaluate predictive performance of two early concentrations and prior pharmacokinetic (PK) information for estimating early exposure. The performance of a modeling approach was compared with a noncompartmental analysis (NCA). A simulation study was performed using literature‐based models for phenytoin (PHT), levetiracetam (LEV), and valproic acid (VPA). These models were used to simulate rich concentration‐time profiles from 0 to 2 h. Profiles without residual unexplained variability (RUV) were used to obtain the true partial area under the curve (pAUC) until 2 h after the start of drug infusion. From the profiles with the RUV, two concentrations per patient were randomly selected. These concentrations were analyzed under a population model to obtain individual population PK (PopPK) pAUCs. The NCA pAUCs were calculated using a linear trapezoidal rule. Percent prediction errors (PPEs) for the PopPK pAUCs and NCA pAUCs were calculated. A PPE within ±20% of the true value was considered a success and the number of successes was obtained for 100 simulated datasets. For PHT, LEV, and VPA, respectively, the median value of the success statistics obtained using the PopPK approach of 81%, 92%, and 88% were significantly higher than the 72%, 80%, and 67% using the NCA approach (p < 0.05; Mann–Whitney U test). This study provides a means by which early exposure can be estimated with good precision from two concentrations and a PopPK approach. It can be applied to other settings in which early exposures are of interest.

Early Exposure of Fosphenytoin, Levetiracetam, and Valproic Acid After High-Dose Intravenous Administration in Young Children With Benzodiazepine-Refractory Status Epilepticus

Fosphenytoin (FOS) and its active form, phenytoin (PHT), levetiracetam (LEV), and valproic acid (VPA) are commonly used second-line treatments of status epilepticus. However, limited information is available regarding LEV and VPA concentrations following high intravenous doses, particularly in young children. The Established Status Epilepticus Treatment Trial, a blinded, comparative effectiveness study of FOS, LEV, and VPA for benzodiazepine-refractory status epilepticus provided an opportunity to investigate early drug concentrations. Patients aged ≥2 years who continued to seizure despite receiving adequate doses of benzodiazepines were randomly assigned to FOS, LEV, or VPA infused over 10 minutes. A sparse blood-sampling approach was used, with up to 2 samples collected per patient within 2 hours following drug administration. The objective of this work was to report early drug exposure of PHT, LEV, and VPA and plasma protein binding of PHT and VPA. Twenty-seven children with median (interquartile range) age of 4 (2.5-6.5) years were enrolled. The total plasma concentrations ranged from 69 to 151.3 μg/mL for LEV, 11.3 to 26.7 μg/mL for PHT and 126 to 223 μg/mL for VPA. Free fraction ranged from 4% to 19% for PHT and 17% to 51% for VPA. This is the first report in young children of LEV concentrations with convulsive status epilepticus as well as VPA concentrations after a 40 mg/kg dose. Several challenges limited patient enrollment and blood sampling. Additional studies with a larger sample size are required to evaluate the exposure-response relationships in this emergent condition.