Seizure freedom and plasma levels of newer generation antiseizure medications

Clinical value of saliva therapeutic drug monitoring of newer antiseizure medications

INTRODUCTION

Saliva is a promising option for therapeutic drug monitoring, with studies since the 1970s indicating a good correlation between plasma and saliva levels for early anti-seizure medications, although limited data exist for newer generation drugs.

OBJECTIVES

To evaluate the reliability and predictive power of saliva as a minimally invasive surrogate marker of plasma concentration for the routine therapeutic drug monitoring (TDM) of newer anti-seizure medications (ASM).

METHODS

We collected blood samples at steady state in patients at least 6 h post-dose, paired with unstimulated saliva samples. We evaluated the correlation between plasma and saliva drug levels and the positive and negative predictive value for plasma values extrapolation from saliva levels. A very low saliva level was defined as below half the plasma lower reference limit.

RESULTS

294 adult patients (53 % male) with a mean age of 40 (SD: 16) were enrolled and 589 paired saliva-plasma samples were quantified. The highest significant correlations between saliva and plasma were observed for zonisamide (R2: 0.92) perampanel (0.91), brivaracetam (0.87), followed by topiramate, lamotrigine, lacosamide (0.76-0.68), and rufinamide, levetiracetam, pregabalin (0.63-0.55). No significant correlation was found for the active mono-hydroxy derivative of oxcarbazepine. Despite a good correlation coefficient, the correlations between saliva and plasma levels were generally loose, resulting in a broad predicted range of plasma levels for a given saliva level. Nonetheless, very low saliva levels exhibited strong specificity in predicting low plasma levels, with 87 % to 100 % accuracy, and when saliva levels fell below the limit of quantification, all corresponding plasma levels were below reference ranges.

CONCLUSIONS

This large newer ASM paired plasma-saliva collection allows to precise the potential use of saliva in the management of epilepsy, especially for commonly used ASM such as lamotrigine and levetiracetam. Although they correlate well, extrapolating plasma levels from saliva samples is still an imprecise approximation, making it inadequate for fine dosage adjustments. Yet, a very low saliva level has an appreciable discriminative ability for low plasma level. Unstimulated saliva represents a convenient non-invasive alternative to plasma, to readily identify compliance issues or major drug-drug interactions.

Clinical impact of therapeutic drug monitoring for newer anti-seizure medications in patients with epilepsy: A real-world observation study

BACKGROUND

The clinical value of therapeutic drug monitoring (TDM) for newer anti-seizure medications (ASMs) remains uncertain. This study aimed to assess the impact of newer ASM TDM on clinical decision making in patients with epilepsy.

METHODS

We retrospectively identified all plasma requests for newer ASM level measurement as part of routine clinical management in the outpatient departments of seven medical institutes across Taiwan between September 2016 and May 2019. Data collected from reviewed medical records included clinical and medication details, indications for TDM requests, test results, interpretation, and impact on patient management.

RESULTS

A total of 682 visits with 1051 plasma samples were included. The most frequently analyzed ASMs were levetiracetam (36.1%), oxcarbazepine (18.4%), and lamotrigine (12.0%). Reasons for TDM included poorly controlled seizures (55.3%), concerns about drug-drug interactions (12.3%), and suspicion of drug overdose (10.6%). 68.8% of samples were within the orienting therapeutic range, even for patients with poorly controlled seizures. TDM for non-adherence concerns showed 54.3% below the orienting therapeutic range, while ASM-related adverse events assessment only 8.9% showed levels exceeding the orienting therapeutic range. Following TDM results, 64.2% of cases had medication adjustments, mainly dosage increases. Overall, 55.9% of newer ASM TDM visits showed improved outcomes, including reduced seizures (47.5%) and fewer ASM-related side effects (8.4%).

CONCLUSIONS

These findings suggest that appropriate utilization of TDM for newer ASMs provides clinical benefits in adjunct to complement clinical decision making in the management of epilepsy patients in a real-world clinical setting.

Monitoring levetiracetam concentration in saliva during pregnancy is stable and feasible

AIMS

This multicenter prospective cohort study (registration no. ChiCTR2000032089) aimed to investigate the relationship between saliva and plasma levetiracetam concentrations to determine whether saliva could be used for routine monitoring of levetiracetam during pregnancy.

METHODS

The slot concentrations of levetiracetam in simultaneously obtained saliva and plasma samples were measured using UPLC-MS/MS. The correlations between saliva and plasma levetiracetam concentrations and the dose-normalized concentrations were compared among pregnant women in different stages and nonpregnant control participants with epilepsy.

RESULTS

In total, 231 patients with 407 plasma and saliva sample pairs were enrolled from 39 centers. Linear relationships between salivary and plasma levetiracetam concentrations were reported in the enrolled population (r = 0.898, p < 0.001), including pregnant (r = 0.935, p < 0.001) and nonpregnant participants (r = 0.882, p < 0.001). Plasma concentrations were moderately higher than saliva concentrations, with ratios of saliva to plasma concentrations of 0.98 for nonpregnant women, 0.98, 1, and 1.12 for pregnant women during the first trimester, the second trimester, the and third trimester, respectively. The effective range of saliva levetiracetam concentration was found to be 9.98 μg/mL (lower limit) with an area under the curve (AUC) of 0.937 (95% confidence intervals, 0.915-0.959), sensitivity of 88.9%, specificity of 86.8%, and p < 0.001, to 24.05 μg/mL (upper limit) with an AUC of 0.952 (0.914-0.99), sensitivity of 100%, specificity of 92.3%, and p = 0.007.

CONCLUSION

The saliva/plasma concentration ratio of levetiracetam remains constant during pregnancy and is similar to that in non-pregnant individuals. Monitoring levetiracetam concentration in saliva during pregnancy should be widely promoted.

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.

Treatment-emergent adverse events and antiseizure medication actual drug load

OBJECTIVE

The correlation between treatment-emergent adverse events (TEAE) and antiseizure medication (ASM) drug load is a controversial topic. Previous studies used daily defined dosage (DDD) to measure drug load. We aim to assess if ASM adjusted to body weight and plasma levels were associated with TEAE.

METHODS

We analyzed clinical visits of a trial on therapeutic drug monitoring in outpatients with epilepsy. TEAE, treatment, and its changes, as well as ASM plasma levels, were recorded at each visit. Each medication level was stratified according to its position in relation to its proposed reference range (below, in the lower half, upper half, or above).

RESULTS

We analyzed 424 visits (151 participants). Treatment-emergent adverse events were reported in 84 (20%) visits. There was no significant difference when comparing visits with TEAE with those without TEAE in terms of ASM drug load (calculated with DDD), corrected for body weight, their changes since the last visit, as well as summed plasma levels compared to reference ranges.

SIGNIFICANCE

Actual drug load seems not to represent a major determinant of TEAE recorded during routine visits, even when accounting thoroughly for the patient's exposure to the treatment. The use of structured questionnaires and neuropsychometric tests may assess more accurately the potential consequences of drug loads.

Pregabalin Add-On vs. Dose Increase in Levetiracetam Add-On Treatment: A Real-Life Trial in Dogs With Drug-Resistant Epilepsy

Epilepsy is a common neurological disorder affecting 0.6–0.75% of dogs in veterinary practice. Treatment is frequently complicated by the occurrence of drug-resistant epilepsy and cluster seizures in dogs with idiopathic epilepsy. Only few studies are available to guide treatment choices beyond licensed veterinary drugs. The aim of the study was to compare antiseizure efficacy and tolerability of two add-on treatment strategies in dogs with drug-resistant idiopathic epilepsy. The study design was a prospective, open-label, non-blinded, comparative treatment trial. Treatment success was defined as a 3-fold extension of the longest baseline interseizure interval and to a minimum of 3 months. To avoid prolonged adherence to a presumably ineffective treatment strategy, dog owners could leave the study after the third day with generalized seizures if the interseizure interval failed to show a relevant increase. Twenty-six dogs (mean age 5.5 years, mean seizure frequency 4/month) with drug-resistant idiopathic epilepsy and a history of cluster seizures were included. Dogs received either add-on treatment with pregabalin (PGB) 4 mg/kg twice daily (14 dogs) or a dose increase in levetiracetam (LEV) add-on treatment (12 dogs). Thirteen dogs in the PGB group had drug levels within the therapeutic range for humans. Two dogs in the PGB group (14.3%; 2/14) and one dog in the LEV group (8.3%; 1/12) achieved treatment success with long seizure-free intervals from 122 to 219 days but then relapsed to their early seizure frequency 10 months after the study inclusion. The overall low success rates with both treatment strategies likely reflect a real-life situation in canine drug-resistant idiopathic epilepsy in everyday veterinary practice. These results delineate the need for research on better pharmacologic and non-pharmacologic treatment strategies in dogs with drug-resistant epilepsy.

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.

Therapeutic drug monitoring of newer generation antiseizure medications at the point of treatment failure

PURPOSE

The benefit of therapeutic drug monitoring (TDM) of newer generation antiseizure medications (ASM) has been little studied. A recent randomized study suggested that TDM at each medical visit did not bring a significant benefit, but the study did not investigate TDM in cases of treatment failure. Accordingly, we realized a post hoc analysis of this trial.

METHODS

We analyzed 282 TDMs in 136 patients. We compared TDM performed at visits after treatment failure versus without treatment failure, reporting the proportion of drug levels out of range and the prescriber's adherence to dosage recommendations according to measured drug levels.

RESULTS

There was no statistical difference in terms of proportion of out of range plasma drug levels (47% vs 50%, p = 0.7) or adherence of prescribers to the clinical pharmacologists' dosage recommendations (21% vs 30%, p = 0.6) between visits after treatment failure and visits without treatment failure, respectively. Knowledge of prior drug levels did not modify the results.

CONCLUSION

Systematic TDM at appointments following treatment failure showed similar results to TDM at visits without treatment failure. The prescribers' adherence with dosage recommendations was low in both cases. It is not clear whether better prescriber adherence would improve patient outcome. Furthermore, the ability to detect poor patient compliance is limited in a planned outpatient appointment. The study setting does not reflect on the general usefulness of TDM.