Antiepileptic Monitoring Research Articles

External validation of the AntiEpileptic Drug Monitoring in PREgnancy (EMPiRE) model for predicting seizures in pregnant women with epilepsy

BackgroundThe AntiEpileptic Drug Monitoring in PREgnancy (EMPiRE) model is the only available tool for predicting seizures in pregnant women with epilepsy (WWE) using anti-seizure medications (ASMs); however, its predictive performance requires validation. This study aimed to evaluate the predictive ability of this model in pregnant Chinese WWE and its potential usefulness in clinical practice.MethodsData of the EMPiRE model were derived from the EMPiRE study, a prospective multicenter cohort study that recruited women on ASM monotherapy (lamotrigine, carbamazepine, phenytoin or levetiracetam) or polytherapy (lamotrigine with either carbamazepine, phenytoin or levetiracetam). Based on the applicable population of the EMPiRE model, we evaluated 280 patients registered in the Wenzhou Epilepsy Follow-up Registry Database from January 1, 2010, to December 31, 2020. A total of 158 eligible patients were included in the validation cohort. We collected data on the baseline characteristics of patients, eight predictors of the EMPiRE model and outcome events. The outcome was the occurrence of tonic-clonic or non-tonic-clonic seizures at any time in pregnancy up to 6 weeks postpartum. We used the equation of the EMPiRE model to obtain the predicted probabilities of seizures. The predictive ability of the EMPiRE model was quantified by the C-statistic (scale 0–1, values > 0.5 show discrimination), GiViTI calibration test and decision curve analysis (DCA).ResultsOf 158 eligible patients, 96 patients (60.8%, 96/158) experienced one or more seizures at any time between pregnancy and 6 weeks postpartum. The EMPiRE model showed good discrimination with a C-statistic of 0.76 (95% confidence interval [CI] 0.70–0.84). The GiViTI calibration belt showed that the predicted probabilities, which ranged from 16 to 96% (95% CI), were lower than the actual probabilities. DCA indicated that the highest net proportional benefit was obtained for predicted probability thresholds of 15–18% and 54–96%.ConclusionsThe EMPiRE model could discriminate well between WWE with and without seizures during pregnancy and 6 weeks postpartum, but the risk of seizures may be underestimated. The limitations of the model for specific medication regimens may limit its real-world application. If the model is further improved, it will be incredibly valuable.

Simultaneous determination of 24 antiepileptic drugs and their active metabolites in human plasma by UHPLC-MS/MS

Antiepileptic drugs (AEDs) have narrow therapeutic ranges with large individual variability. Routine therapeutic drug monitoring of AEDs was useful for dose optimization, but the common immunoassays could not meet the detection requirements of AEDs, especially for new generation AEDs. The aim of this study was to validate an ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method for simultaneously quantification of 24 AEDs and their active metabolites in human plasma and comparison with a chemiluminescent immunoassay (Simens ADVIA Centaur). The method validation was performed according to FDA and EMEA guidelines. A one-step protein precipitation by acetonitrile followed a five-fold dilution was performed for sample pretreatment. A 5.2 min gradient separation by methanol and 10 mM ammonium acetate was used for separation at 0.6 mL/min under 45 °C. Both positive and negative electrospray ionization were used. Isotopic internal standard was used for all analytes. The inter-day (36 days) accuracy and precision of quality control samples were − 1.07–13.69% and < 6.70% for all analytes. The stability was acceptable for all analytes under routine storing conditions. A total of 436 valproic acid, 118 carbamazepine, and 65 phenobarbital samples were determined twice by each of the UHPLC-MS/MS and immunoassay. Evaluated by Bland-Altman plot, the mean overestimation of the immunoassay compared to UHPLC-MS/MS was 16.5% for valproic acid, 5.6% for carbamazepine, and 40.3% for phenobarbital.

Disposable Sensor Chips with Molecularly Imprinted Carbon Paste Electrodes for Monitoring Anti-Epileptic Drugs.

Epilepsy is a neurological disorder that affects millions of people worldwide. Anti-epileptic drugs (AEDs) are critical for their management. However, the therapeutic window is narrow, and traditional laboratory-based therapeutic drug monitoring (TDM) methods can be time consuming and unsuitable for point-of-care testing. To address this issue, we developed a disposable sensor chip based on molecularly imprinted polymer-modified carbon paste electrodes (MIP-CPs) for the TDM of AEDs such as phenobarbital (PB), carbamazepine (CBZ), and levetiracetam (LEV). In this work, functional monomers (methacrylic acid) and crosslinking monomers (methylene bisacrylamide and ethylene glycol dimethacrylate) were copolymerized in the presence of the AED template and grafted on the graphite particles by simple radical photopolymerization. The grafted particles were mixed with silicon oil, dissolving ferrocene as a redox marker to make the MIP-carbon paste (CP). Disposable sensor chips were fabricated by packing the MIP-CP into the base made of poly (ethylene glycol terephthalate) (PET) film. The sensor's sensitivity was determined using differential pulse voltammetry (DPV), carried out on a single sensor chip for each operation. Linearity was obtained from 0-60 μg/mL in PB and LEV and 0-12 μg/mL in CBZ, covering their respective therapeutic range. The time taken for each measurement was around 2 min. The experiment using whole bovine blood and bovine plasma indicated that the existence of species that interfered had a negligible effect on the test's sensitivity. This disposable MIP sensor provides a promising approach for point-of-care testing and facilitating the management of epilepsy. Compared with existing tests, this sensor offers a faster and more accurate way to monitor AEDs, which is crucial for optimizing therapy and improving patient outcomes. Overall, the proposed disposable sensor chip based on MIP-CPs represents a significant advancement in AED monitoring, with the potential for rapid, accurate, and convenient point-of-care testing.

Thyroid functions as a parameter in monitoring of antiepileptic drugs

ABSTRACT Introduction Epilepsy is a chronic neurological disorder that is treated with multiple medications that can have significant side effects. This study investigated the potential effects of antiepileptic drugs on thyroid function. Methods The participants in this study were epileptic adults who had been consistently monitored in follow-up care. The effects of antiepileptic drugs on the serum levels of the thyroid stimulating hormone (TSH), free T3 (fT3), and free T4 (fT4) of these patients were investigated retrospectively by comparing laboratory recordings in three defined periods: prior to antiepileptic drug treatment, between 6 months and 1 year of treatment (early stage), and after 1 year of treatment (late stage). Results A total of 300 epileptic patients (F/M: 175/125) were included in the study. Significant differences in TSH and fT4 serum levels in the late stage compared to the pre-treatment stage (p = 0.006 and p = 0.0005, respectively) were found. TSH values in the late stage of treatment were abnormally high in one case and low in five cases; all six of these cases had normal pre-treatment and early-stage TSH values. Patients who received monotherapy with valproic acid, levetiracetam or carbamazepine were evaluated separately and there was no statistically significant difference in TSH and fT3 levels, while fT4 levels were significantly increased during treatment in each treatment group. Conclusions A significant increase in TSH levels was found in epileptic patients on polytherapy. Our results give us the opportunity to highlight the potential unique or cumulative effect of antiepileptic drugs on thyroid hormone levels.

Feasibility of Using Oral Fluid for Therapeutic Drug Monitoring of Antiepileptic Drugs.

Therapeutic drug monitoring (TDM) of antiepileptic drugs (AED) using blood is well established but limited by its invasiveness, accessibility, cost, interpretation errors, and related disturbances in protein binding. TDM using oral fluid (OF) could overcome these limitations. This paper provides a summary of the current evidence for using OF as a matrix to perform TDM of AEDs, as well as practical considerations. A literature search of MEDLINE, EMBASE, and the Cochrane Library was conducted on April 9, 2018 (and then updated on May 20, 2020) using all AEDs as keywords along with "oral fluid," "saliva," "salivary," "seizure," "epilepsy," "antiepileptic," and "anticonvulsant." A total of 18 relevant articles were found and included in this review. There is evidence to suggest that AED TDM using OF is feasible and that reference ranges can be calculated for the following drugs: carbamazepine, ethosuximide, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, phenobarbital, phenytoin, primidone, topiramate, and valproic acid. For all other AEDs, there is either a lack of evidence on the feasibility of TDM using OF or the evidence indicates that TDM using OF is not feasible. Practical considerations should include the timing and method of OF collection (stimulated or unstimulated) due to their probable impact on the reliability of AED TDM. Using OF may improve the acceptability and accessibility and reduce the cost of AED TDM. Clinical implementation requires standardized collection protocols, more rigorously defined OF reference ranges, and further studies to determine the relevance to clinically important outcomes.

Retrospective Analysis of Pediatric and Adult Populations Using an LC-MS/MS Method for Oxcarbazepine/Eslicarbazepine Metabolite.

Therapeutic drug monitoring of anti-epileptic drugs is important to manage seizure control in patients with epilepsy. Oxcarbazepine is a second-generation anti-epileptic drug approved for use in pediatric patients, and eslicarbazepine acetate is a newer generation drug used as adjunctive therapy and monotherapy for partial-onset (focal) seizures. While several second and third generation anti-epileptic drugs have broader therapeutic efficacy in patients, these drugs can still have severe side effects and variable interpatient pharmacokinetics. Consequently, there is a need for accurate and sensitive analytical methods to support therapeutic drug monitoring. An assay improvement for a LC-MS/MS method was developed for the major metabolite of oxcarbazepine and eslicarbazepine, licarbazepine (MHD), using a 13C-labeled form of the compound as the internal standard. Additionally, retrospective data analysis was used to compare the distribution of results observed in adult vs pediatric patients. Accuracy and linearity across the analytical measuring range of 1 to 60 µg/mL was acceptable. Inter- and intra-run precision was less than 6% at 3 concentrations tested. The limit of detection was determined to be 0.5 µg/mL. Significant interference from hemolysis, icterus, lipemia, or 187 other potential interferences was not detected. The improved assay for MHD was appropriate for clinical use. Retrospective data analysis showed that pediatric and adult patients had a similar distribution of oxcarbazepine/eslicarbazepine metabolite concentrations in serum.

Therapeutic monitoring of antiepileptic drugs: Recommendations to improve care of patients with epilepsy in the Palestinian practice

BackgroundTherapeutic drug monitoring (TDM) can play a major role in optimizing pharmacotherapy of epilepsy. This study was conducted to explore views and opinions of clinicians who care for patients with epilepsy (PWE) in Palestine and to develop consensus-based recommendations with regard to importance, justification, technical, and analytical issues of TDM of antiepileptic drugs (AEDs). MethodsThe study was conducted in three phases: (1) the published literature was thoroughly searched for an initial list of items relevant to TDM of AEDs, (2) the list was supplemented by items provided by key experts (n = 8) through semi-structured in-depth interviews, (3) views and opinions of clinicians (n = 20) on TDM of AEDs were explored, and (4) a two-round Delphi technique was followed among a panel of experts (n = 27) to develop consensus-based recommendations to guide TDM of AEDs in Palestine. ResultsConsensus was achieved on items related to importance (8 items) of TDM of AEDs, clinical justifications of TDM of AEDs (19 items), guidelines for optimal TDM of AEDs (11 items), TDM of some AEDs (21 items), TDM practice (24 items), and some technical and analytical issues in TDM of AEDs (13 items). ConclusionConsensus-based recommendations that might be used in guiding TDM of AEDs in Palestine were developed. Future studies are still needed to investigate if these consensus-based recommendations can improve healthcare of PWE in Palestine.

Dried Blood Microsampling-Based Therapeutic Drug Monitoring of Antiepileptic Drugs in Children With Nodding Syndrome and Epilepsy in Uganda and the Democratic Republic of the Congo.

Nodding syndrome is a highly debilitating, generalized seizure disorder, affecting children in subregions of sub-Saharan Africa. Despite numerous efforts to uncover the etiology, the exact cause of this syndrome still remains obscure. Therefore, to date, patients only receive symptomatic care, including the administration of first-generation antiepileptic drugs for seizure control. As data on the efficacy of drugs within this population are completely lacking, the aim of this study was to explore how therapeutic drug monitoring could help to understand the differential response to therapy. Considering the challenging environment in which sampling had to be performed (remote areas, devoid of electricity, running water, etc), dried blood matrices [ie, dried blood spots (DBSs)] and volumetric absorptive microsampling (VAMS) were considered fit-for-purpose. In addition, owing to the similarities between the syndrome and other forms of epilepsy, samples originating from patients suffering from (onchocerciasis-associated) epilepsy were included. In total, 68 patients with Nodding syndrome from Uganda, 58 Ugandan patients with epilepsy, and 137 patients with onchocerciasis-associated epilepsy from the Democratic Republic of the Congo were included. VAMS samples and DBS were analyzed using validated methods, involving manual extraction or fully automated extraction, respectively, before quantification using liquid chromatography coupled with tandem mass spectrometry. Analysis revealed that serum concentrations (calculated from DBS) within the respective reference ranges were attained in only 52.9% of the 68 Nodding syndrome patients treated with valproic acid, in 21.4% of the 56 Ugandan epilepsy patients treated with carbamazepine, and in 65.7% of the 137 onchocerciasis-associated epilepsy patients from the Democratic Republic of the Congo treated with phenobarbital. In all other instances, concentrations were subtherapeutic. Furthermore, on comparing DBS with VAMS concentrations, an inexplicable overestimation was observed in the latter. Finally, no obvious link could be observed between the obtained drug concentrations and the number of seizures experienced during the last month before sampling, elaborating the fact that the level of improvement in some patients cannot simply be linked to reaching therapeutic concentrations.

Usefulness of saliva for perampanel therapeutic drug monitoring.

Therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) helps optimize drug management for patients with epilepsy. Salivary testing is both noninvasive and easy, and has several other advantages. Due to technical advances, salivary TDM has become feasible for several drugs, including AEDs, and its value has been investigated. Until recently, saliva TDM of perampanel (PER) had not been reported. The purpose of our study was to confirm whether saliva is a biological substitute for plasma in PER TDM. Adult patients diagnosed with epilepsy who received PER from August 2018 to March 2019 at Seoul National University Hospital were enrolled. Total and free PER were measured in simultaneously obtained plasma and saliva samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-performance liquid chromatographic (HPLC). We examined the correlations between saliva and plasma PER concentrations and whether the use of concomitant medications classified as cytochrome P450 (CYP)3A4 inducers affected the correlations. Thirty patients were enrolled, aged 16 to 60; 10 (33%) were women. Patients received 2 to 12mg (mean, 6mg) of PER. The average total and free concentrations of PER were 343.02 (46.6-818.0) and 1.53 (0.51-2.92) ng/mL in plasma and 9.74 (2.21-33.0) and 2.83 (1.01-6.8) ng/mL in saliva, respectively. A linear relationship was observed between the total PER concentrations in saliva and the total and free PER concentrations in plasma (both P<.001; r=.678 and r=.619, respectively). The change in the PER concentration caused by the CYP3A4 inducer did not affect the correlation between saliva and plasma concentrations (all P<.001). The PER concentration in saliva was correlated with that in plasma. This correlation was not affected by CYP3A4 inducers. Our results demonstrate for the first time that PER is measurable in saliva and suggest the potential for the clinical application of the saliva PER TDM matrix.

Determination of Perampanel in Dried Plasma Spots: Applicability to Therapeutic Drug Monitoring.

Although therapeutic drug monitoring of antiepileptic drugs is typically based on the analysis of plasma samples, alternative matrices, such as dried plasma spots (DPSs), may offer specific advantages. The aims of this work were to (1) develop and validate a bioanalytical method for the quantitative determination of the second-generation antiepileptic drug perampanel in DPSs; (2) assess short- and long-term stability of perampanel in DPSs; and (3) test the clinical applicability of the developed method. Two hundred microliters of plasma were dispensed on a glass paper filter and dried. Glass paper filter discs were then inserted into clean tubes. After addition of the internal standard (ie, promethazine), the analytes were extracted with 5-mL methanol, dried at room temperature (23 ± 2°C), and reconstituted. Separation and quantification were achieved on 2 serial reverse-phase monolithic columns connected to an UV detector (λ = 320 nm). Calibration curves were linear in the validated concentration range (25-1000 ng/mL). Intraday and interday accuracy were in the range of 99.2%-111.4%, whereas intraday and interday precision (coefficient of variation) ranged from 2.8% to 8.6%. The lowest limit of quantitation was 25 ng/mL. The stability of the analyte in DPSs was assessed and confirmed under different storage conditions. Perampanel concentrations estimated in DPS samples from patients receiving therapeutic doses were equivalent to those measured in plasma samples. This simple method enables the quantitation of perampanel in DPSs with adequate accuracy, precision, specificity, and sensitivity. The short- and long-term stabilities of perampanel in DPSs are highly beneficial for sample shipment or storage at ambient temperature. Moreover, DPSs decreases the costs associated with storage and transportation compared with conventional wet samples.

Therapeutic drug monitoring of anti-epileptic drugs - a clinical verification of volumetric absorptive micro sampling.

Background Therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) can serve as a valuable tool in optimising and individualising epilepsy treatment, especially in vulnerable groups such as pregnant women, the elderly and children. Unfortunately, TDM is often performed suboptimally due to limitations in blood collection. Therefore, we investigated volumetric absorptive micro sampling (VAMS) - a new home-sampling technique. We aimed to evaluate VAMS to determine and quantify the different AEDs and concentrations of 16 different AEDs in whole blood collected by VAMS. Methods Patient blood samples (n = 138) were collected via venepunctures at the Academic Centre for Epileptology Kempenhaeghe. AED concentrations were determined, and these concentrations were used to compare the VAMS method (whole blood) with the conventional method (serum). In addition, the recovery was examined as well as the impact of haematocrit. Finally, AED-spiked blood was used to test the stability of the AEDs inside the micro-sampler devices over a period of time and whether temperature had an effect on the stability. Results VAMS allows for an accurate detection of 16 different AEDs within 2 days after sampling. Deviation in recovery was less than 10% and high correlations were found between VAMS and conventional sampling. Moreover, haematocrit does not have an effect with values between 0.3 and 0.5 (L/L). Finally, although storage temperature of VAMS does affect some AEDs, most are unaffected. Conclusions VAMS enables an accurate detection of a wide variety of AEDs within 2 days after sampling.

Pharmacological monitoring of antiepileptic drugs in epilepsy patients on haemodialysis.

To retrospectively evaluate the pharmacological profiles of antiepileptic drugs (AEDs) in epilepsy patients during haemodialysis using therapeutic drug monitoring data. The serum concentration of AEDs was collected before and after haemodialysis, and the clearance rate and concentration-to-dose ratio were calculated as pharmacological parameters. Thirty-six patients were enrolled in the study (25 males, 11 females; age: 65.3 ± 14.8 years). In 24 of the 36 patients, epilepsy was associated with cerebrovascular disorders, and diabetes was the most common reason for haemodialysis in 16 patients. With regards to seizure type, focal aware seizures were less frequent than focal impaired awareness seizures and focal-to-bilateral tonic-clonic seizures. Interictal EEG showed intermittent rhythmic slow waves and intermittent slow waves more often than spikes or sharp waves. Levetiracetam was the most commonly used AED and led to the highest percentage of responders (80%; 16/20 patients). However, the clearance rate of levetiracetam during dialysis was highest among the antiepileptic drugs used, requiring supplementary doses after haemodialysis in all 20 patients. Valproic acid was not effective for focal epilepsy for patients on haemodialysis, and non-responders to phenytoin had low serum concentration of phenytoin both before and after haemodialysis. The pre-haemodialysis concentration of levetiracetam tended to be higher than the reference range, suggesting a potential risk of overdosing before haemodialysis. The pre- and post-haemodialysis concentrations of valproic acid tended to be lower than the reference range, suggesting a potential risk of underdosing. The concentration-to-dose ratios for levetiracetam, valproic acid, phenytoin, and carbamazepine were significantly lower after than before haemodialysis. The majority of patients with epilepsy on haemodialysis had cerebrovascular diseases, and therapeutic drug monitoring for levetiracetam, valproic acid, and phenytoin, before and after haemodialysis, is needed to ensure proper dosing.

Reader response: Clinical utility of therapeutic drug monitoring of antiepileptic drugs.

I read with interest the systematic review of Al-Roubaie et al.1 looking at clinical utility of therapeutic drug monitoring (TDM) in the management of patients with epilepsy. I personally have found TDM of limited utility in my patients. Even in the same patient, the drug levels may vary dramatically based on the time the blood sample is drawn relative to the time of ingestion of the antiepileptic drug (AED). Because monitoring is available, there is a tendency to adjust AED dosing based on the level rather than the actual seizure control itself. In a pregnant woman with epilepsy, monitoring needs to be balanced with the dose-dependent risk of major congenital malformations associated with AEDs. Like many things in medicine, TDM has gained acceptance as the standard of care without any scientific evidence to back that claim.

Author response: Clinical utility of therapeutic drug monitoring of antiepileptic drugs.

I appreciated Dr. Sethi's commentary on our recently published article as he raises a number of interesting points.1 Certainly, intraindividual variability is another complicating aspect of therapeutic drug monitoring (TDM) in epilepsy care and, while outside the scope of our review, should be taken into account by all clinicians who choose to incorporate serum antiepileptic drug levels into their clinical decision-making. For my personal practice, I tend to agree that the clinical utility of serum antiepileptic drug levels is limited and that dosing adjustments are best made based on clinical response (seizure control and reported adverse effects). Although our systematic review did identify some studies showing evidence for TDM, the higher quality studies did not show convincing evidence supporting a clinical benefit. In general, we clinicians now have a wealth of diagnostic options available to us, and it is easy to forget that the patient's reported symptoms and clinical examination are almost always the most important outcome measures.

Therapeutic Drug Monitoring of Antiepileptic Drugs in Women with Epilepsy Before, During, and After Pregnancy.

During pregnancy, the pharmacokinetics of an antiepileptic drug is altered because of changes in the clearance capacity and volume of distribution. These changes may have consequences for the frequency of seizures during pregnancy and fetal exposure to antiepileptic drugs. In 2009, a review was published providing guidance for the dosing and therapeutic drug monitoring of antiepileptic drugs during pregnancy. Since that review, new drugs have been licensed and new information about existing drugs has been published. With this review, we aim to provide an updated narrative overview of changes in the pharmacokinetics of antiepileptic drugs in women during pregnancy. In addition, we aim to formulate advice for dose modification and therapeutic drug monitoring of antiepileptic drugs. We searched PubMed and the available literature on the pharmacokinetic changes of antiepileptic drugs and seizure frequency during pregnancy published between January 2007 and September 2018. During pregnancy, an increase in clearance and a decrease in the concentrations of lamotrigine, levetiracetam, oxcarbazepine's active metabolite licarbazepine, topiramate, and zonisamide were observed. Carbamazepine clearance remains unchanged during pregnancy. There is inadequate or no evidence for changes in the clearance or concentrations of clobazam and its active metabolite N-desmethylclobazam, gabapentin, lacosamide, perampanel, and valproate. Postpartum elimination rates of lamotrigine, levetiracetam, and licarbazepine resumed to pre-pregnancy values within the first few weeks after pregnancy. We advise monitoring of antiepileptic drug trough concentrations twice before pregnancy. This is the reference concentration. We also advise to consider dose adjustments guided by therapeutic drug monitoring during pregnancy if the antiepileptic drug concentration decreases 15-25% from the pre-pregnancy reference concentration, in the presence of risk factors for convulsions. If the antiepileptic drug concentration changes more than 25% compared with the reference concentration, dose adjustment is advised. Monitoring of levetiracetam, licarbazepine, lamotrigine, and topiramate is recommended during and after pregnancy. Monitoring of clobazam, N-desmethylclobazam, gabapentin, lacosamide, perampanel, and zonisamide during and after pregnancy should be considered. Because of the risk of teratogenic effects, valproate should be avoided during pregnancy. If that is impossible, monitoring of both total and unbound valproate is recommended. More research is needed on the large number of unclear pregnancy-related effects on the pharmacokinetics of antiepileptic drugs.

Therapeutic Drug Monitoring of Newer Antiepileptic Drugs: A Randomized Trial for Dosage Adjustment.

Therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) is widely established for older generation AEDs, whereas there is limited evidence about newer AEDs. Our aim is to assess the benefit of TDM of newer generation AEDs in epilepsy. We performed a randomized, controlled trial comparing systematic with rescue TDM of lamotrigine, levetiracetam, oxcarbazepine, topiramate, brivaracetam, zonisamide, or pregabalin. Participants were adults with epilepsy, in whom treatment with newer generation AEDs was initiated or needed adjustment. In the systematic TDM arm, AED plasma levels were available at each appointment, whereas in the rescue TDM arm, levels were known only if a study endpoint was reached (inefficacy or adverse events). The primary outcome was the proportion of participants followed 1 year without reaching one of the predefined endpoints. A total of 151 participants were enrolled; global retention in the study was similar in both arms (56% overall, 58% in the systematic, and 53% in the rescue TDM arm, p = 0.6, Cox regression). There was no difference in terms of outcome regarding treatment efficacy or tolerability. Partial adherence of clinicians to TDM (adjusting or not AED dosage based on blood levels) did not explain this lack of benefit. This study provides class A evidence that systematic drug level monitoring of newer generation AEDs does not bring tangible benefits in the management of patients with epilepsy. Poor correlation between clinical effects and drug levels likely accounts for this finding. However, TDM is useful in several situations, such as pregnancy, as well as when there are compliance issues. ANN NEUROL 2020;87:22-29.

Volumetric Absorptive Microsampling: A New Sampling Tool for Therapeutic Drug Monitoring of Antiepileptic Drugs.

Volumetric absorptive microsampling (VAMS) is a novel sampling technique for the collection of fixed-volume capillary blood. In this study, a new analytical method was developed and used to quantify 14 different antiepileptic drugs (AEDs) and 2 active metabolites in samples collected by VAMS. These data were compared with concentration measurements in plasma. The authors developed a selective and sensitive liquid chromatography-mass spectrometry (LC-MS/MS) assay to measure the concentrations of several AEDs in whole blood collected by VAMS, which were compared with a commercially available LC-MS/MS kit for AED monitoring in plasma. Drugs and internal standards were extracted from whole blood/plasma samples by a simple protein precipitation. An LC-MS/MS method analyzing VAMS samples was successfully developed and validated for the determination of various AED concentrations in whole blood according to EMA guidelines for bioanalytical method validation. Extraction recovery was between 91% and 110%. No matrix effect was found. The method was linear for all drugs with R ≥0.989 in all cases. Intra-assay and inter-assay reproducibility analyses demonstrated accuracy and precision within acceptance criteria. Carry over and interferences were negligible. No volumetric HCT% bias was found at 3 different HCT values (35%-55%) with recovery being consistently above 87%. Samples are very stable at temperatures ranging from -20°C to 37°C and for a 4-month period. Leftover EDTA samples from 133 patients were tested to determine concentration differences between plasma and whole blood sampled by VAMS. The resulting difference varied less than 15% apart from those drugs with a blood/plasma ratio (R) different from 1. The assay allows for highly sensitive and selective quantification of several AEDs in whole blood samples collected by VAMS. The developed method is accurate and precise and free from matrix effects and volumetric HCT% bias.

Clinical utility of therapeutic drug monitoring of antiepileptic drugs: Systematic review.

To systematically review and evaluate the available evidence supporting or refuting clinical use of therapeutic drug monitoring (TDM) of antiepileptic drugs (AEDs) in patients with epilepsy. We searched MEDLINE, Embase, BIOSIS, Cochrane, PubMed, Africa-Wide Information, Web of Science, and grey literature. Randomized controlled studies and observational studies that compared the clinical outcomes of TDM vs non-TDM were included. Two reviewers independently extracted the data. The primary outcome was seizure control; adverse effects were considered as secondary outcomes. The PROSPERO ID of this systematic review's protocol is CRD42018089925. Sixteen studies were identified meeting eligibility requirements. Four randomized controlled trials (RCTs), 1 meta-analysis, and 11 quasiexperimental (QE) studies were included in the systematic review. Results from the analysis of RCTs showed no significant positive effect of TDM on seizure outcome (only 25% positive effect of phenytoin). However, some of the QE studies found that TDM was associated with better seizure control or lower rates of adverse effects. The existing evidence from various designs has shown various methodological implications, which warrants inconclusive results and highlights the requirement of more number of studies in this line. If optimally implemented, TDM may enhance clinical care, particularly for phenytoin and other AEDs with complex pharmacokinetics. However, the ideal method for implementation is unclear, and serum drug levels should be considered in context with patient-reported clinical data regarding seizure control and adverse events.

Revisiting clinical practice in therapeutic drug monitoring of first-generation antiepileptic drugs

Due to the complex and diverse nature of epilepsy and antiepileptic drugs (AEDs), the implementation of therapeutic drug monitoring (TDM) can contribute significantly to the overall improvement of clinical outcome in epilepsy. Establishing and interpreting an individual serum drug concentration range by TDM is beneficial to prevent recurrence of epilepsy, as well as to avoid adverse drug effects. It enables optimization of dosage regimen, especially in case of drugs that follow non-linear pharmacokinetics, and in special populations such as pregnancy, pediatrics, geriatrics, critically ill, and liver and renal impairment. This review summarizes the ongoing clinical practice utilizing TDM of first-generation or conventional AEDs, such as valproic acid, phenytoin, carbamazepine, phenobarbital, primidone, ethosuximide, clonazepam, clobazam, piracetam, and sulthiame. Prospective and retrospective data describing the serum drug concentration–efficacy–toxicity relationship, pharmacokinetic parameters, activity of metabolites, overdose and treatment, and drugs that alter pharmacokinetics, have been described. The therapeutic decision should not be finalized based on serum drug concentration alone; other important factors to be considered are clinical laboratory data, patient history, signs and symptoms, pharmacogenetics, and electroencephalogram.

Fully automated therapeutic drug monitoring of anti-epileptic drugs making use of dried blood spots

Fully automated dried blood spot (DBS) extraction systems, online coupled to standard liquid chromatography-tandem mass spectrometry (LC–MS/MS) configurations, decrease the hands-on time associated with conventional DBS analysis, resulting in a higher sample throughput, making the technique more compatible with a high-capacity bioanalytical workflow. The aim of this study was to develop and validate an LC–MS/MS method, using a DBS-MS 500 autosampler, for the determination and quantification of four anti-epileptic drugs (carbamazepine, valproic acid, phenobarbital and phenytoin) and one active metabolite (carbamazepine-10,11-epoxide) in DBS samples. Method development included thorough optimization of the fully automated extraction procedure (i.e. extraction solvent, extraction (loop) volume, internal standard application, internal standard drying time, etc.). The method was fully validated based on international guidelines. Accuracy (%bias), as well as precision (%RSD) (with a single exception) were below 13%. Neither carry-over nor unacceptable interferences were observed. All compounds were stable in DBS for at least 1 month when stored at room temperature, 4 °C and −20 °C and for at least 4 days when stored at 60 °C. Internal standard-corrected matrix effects were below 8%, with %RSDs below 9.1%. Reproducible relative recovery values (around 60% for all analytes) were obtained and the effect of the hematocrit on the relative recovery was overall limited. Successful application on capillary patient samples originating from developing countries demonstrated the applicability of the developed procedure in a remote setting.