An Updated Overview on Therapeutic Drug Monitoring of Recent Antiepileptic Drugs

A paradigm shift in trichinellosis management: curcumin-olive oil nanocomposite's multi-faceted therapeutic approach

BACKGROUND

Trichinella spiralis, a globally widespread zoonotic parasite, poses significant health and economic burdens due to its complex life cycle and the scarcity of effective, multi-stage treatments.

METHODS

This study investigated the therapeutic potential of a novel curcumin-olive oil nanocomposite (CO-NC) against three critical stages of T. spiralis infection in a murine model: adult worms (3-5 days post-inoculation, dpi), newborn larvae (8-10 dpi), and encapsulated larvae (33-35 dpi). CO-NC exhibited potent, stage-specific, and dose-dependent antiparasitic activity.

RESULTS

Remarkably, a 100 mg/kg dose achieved complete eradication of both newborn and encapsulated larvae, mirroring the efficacy of the current standard treatment, albendazole (50 mg/kg). This high dose also significantly reduced adult worm burdens by 91.6%. Even at a lower dose of 50 mg/kg, CO-NC demonstrated substantial activity, reducing adult worms and encapsulated larvae by 55.2% and 43.8%, respectively. Beyond its direct antiparasitic effects, CO-NC (100 mg/kg) significantly mitigated infection-induced oxidative stress by restoring key redox markers in muscle and intestinal tissues, including xanthine oxidase, glutathione, malondialdehyde, and total antioxidant capacity. Furthermore, complementary in vitro studies revealed superior anticancer and anti-inflammatory properties of CO-NC compared to crude curcumin and standard reference compounds at their respective IC50 values.

CONCLUSIONS

These findings highlight CO-NC as a promising multi-faceted therapeutic candidate for trichinellosis, offering potent antiparasitic efficacy comparable to albendazole alongside valuable antioxidant, anti-inflammatory, and anticancer properties. This integrated approach underscores the potential of CO-NC as an innovative and comprehensive solution for the challenges posed by T. spiralis infections.

Co-crystallization in Antiepileptic Drugs: A Path Toward Better Therapeutic Outcomes

Pharmaceutical cocrystals are highly valued in drug development as they can enhance active pharmaceutical ingredients (APIs)' physicochemical characteristics without changing their chemical structure. This is especially important for biopharmaceutical classification system (BCS) class II and IV drugs, which have poor water solubility, resulting in low bioavailability. Co-crystallization is the process of forming a crystalline solid where the API and a co-former are combined in a specified stoichiometric proportion within a crystal lattice, mainly stabilized by non-covalent interactions. This method can enhance properties like stability, dissolution rate, solubility, compressibility, and powder flowability and pharmacokinetics, resulting in an improved drug delivery system and therapeutic effectiveness. Pharmaceutical antiepileptic drugs (AEDs) are the main focus of this review. Pharmaceutical characteristics, conventional and advanced cocrystal generation, and assessment techniques, as well as recent developments related to cocrystals, may suggest perception for cocrystal potential, design approaches, and regulatory aspects. The study's overall finding emphasizes the growth of co-crystallization as a significant technique to enhance the drug's performance and also demonstrates its potential as a significant technique in the AED category and its future application.

Physiologically based pharmacokinetic modeling and simulation of topiramate in populations with renal and hepatic impairment and considerations for drug-drug interactions

Topiramate (TPM) is a broad-spectrum antiepileptic drug (AED) commonly prescribed for approved and off-label uses. Routine monitoring is suggested for clinical usage of TPM in special population due to its broad side effect profile. Therefore, it is crucial to further explore its pharmacokinetic characteristics. Physio-chemical properties of TPM were initially determined from online database and further optimized while establishing the PBPK model for healthy adults using the PK-Sim software. The model was then extrapolated to patients with renal impairment and patients who were hepatically impaired. A drug-drug interaction (DDI) model was also built to simulate plasma TPM concentrations while concomitantly used with carbamazepine (CBZ). The goodness-of-fit method and average fold error (AFE) method were used to compare the differences between predicted and observed values to assess the accuracy of the PBPK model. Almost all of the predicted concentration fell within twofold error range of corresponding observed concentrations. The AFE ratio of predicted to observed values of Cmax and AUC0-inf was all within 0.5 and 2. It is recommended that the doses be reduced to 70%, 50%, and 40% of the healthy adult dose for the chronic kidney disease (CKD) stage 3, stage 4, and stage 5 patients, respectively, and reduced to ~70%, and 35% for the Child-Pugh-B, and Child-Pugh C scored patient with hepatic impairment, respectively. If TPM is co-administered with CBZ, increasing TPM doses to 150%-175% of the monotherapy dose is recommended according to model simulation.

Prolonged Elimination of Lamotrigine After Suicidal Overdose: A Case Report

Lamotrigine (LTG) is an antiepileptic drug that stabilizes neuronal membranes by inhibiting excitatory neurotransmitter release, thereby reducing neuronal excitation. Various factors can contribute to its metabolic dysfunction. A 22-year-old female with bipolar disorder presented after intentionally ingesting 216 tablets, including LTG (4,100 mg), prescribed antipsychotics, over-the-counter cold medicine containing acetaminophen (27 g), and alcohol. She arrived at the hospital approximately one-hour post-ingestion in a confused state, with mild transaminase elevation but no significant electrocardiographic abnormalities. Initial management included activated charcoal, N-acetylcysteine therapy, and intravenous fluids. Despite these interventions, she deteriorated to a comatose state by hospital day two, accompanied by a mild skin rash later diagnosed as urticaria. Her hepatic function and consciousness gradually improved, with transaminase normalization and full neurological recovery by day six. She was discharged on day seven without residual deficits. Serial LTG serum measurements at 13, 55, and 79 hours post-ingestion (16.10 mg/L, 12.39 mg/L, and 6.84 mg/L, respectively) revealed a non-linear elimination pattern, with an estimated half-life of ~100 hours between the first two measurements. However, by the third measurement, elimination aligned with previously reported pharmacokinetics. The patient's young age, normal BMI, absence of hepatic disease, and minimal interaction potential with co-ingested antipsychotics did not explain the delayed LTG clearance. We hypothesize that hepatic metabolic pathway saturation led to this non-linear pharmacokinetic behavior. The resolution of delayed elimination corresponded with hepatic enzyme normalization. In drug overdose cases, prolonged consciousness disturbance may indicate an extended drug half-life due to metabolic dysfunction. If recovery exceeds expectations, further evaluation is warranted to identify and address potential causes.

Efficacy and Blood Levels of Lacosamide in Patients with Focal Epilepsy

Objectives: The aim of this paper is to analyze clinical targets for lacosamide (LCM) blood levels in patients with focal epilepsy. Referring to the LCM optimal range will encourage us to think about the importance and usefulness of measuring its blood levels. Methods: A total of 101 (45 female, 56 male) patients were treated with LCM. Blood sampling was performed 1 month after the start of oral medication (the levels reached a steady state) if the LCM treatment had been continued, and then 6 and 12 months after. The efficacy of LCM was evaluated by the reduction in the epileptic seizure rate (RR) at the time of blood sampling. The patients were classified as effective cases (seizure reduction rate ≥ 50%) and ineffective cases (<50%). The actual level, the calculated peak/trough levels, and the levels for each type of seizure were investigated. A statistical analysis was performed using Spearman's rank correlation coefficient and the Wilcoxon signed-rank test. Results: A positive correlation was seen between blood levels and dosage (r = 0.446). However, the blood levels and RR showed no correlation. The blood levels were higher in effective cases than in ineffective cases at all time points (measurement p < 0.001, peak p = 0.013, trough p = 0.001). Because the range was set so that the effective and ineffective groups did not overlap, the optimal range of LCM was found to be 8.0-10.5 µg/mL. Conclusions: Measuring and calculating blood levels of LCM and adjusting the dosage to reach the optimal range are recommended. Moreover, the optimal range for LCM was determined as a therapeutic target.

Innovative LC-MS/MS method for therapeutic drug monitoring of fenfluramine and cannabidiol in the plasma of pediatric patients with epilepsy

We present a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying fenfluramine (FFA), its active metabolite norfenfluramine (norFFA), and Epidyolex®, a pure cannabidiol (CBD) oral solution in plasma. Recently approved by the EMA for the adjunctive treatment of refractory seizures in patients with Dravet and Lennox-Gastaut syndromes aged above 2 years, FFA and CBD still do not have established therapeutic blood ranges, and thus need careful drug monitoring to manage potential pharmacokinetic and pharmacodynamic interactions. Our method, validated by ICH guidelines M10, utilizes a rapid extraction protocol from 100 µL of human plasma and a reversed-phase C-18 HPLC column, with deuterated internal standards. The Thermofisher Quantiva triple-quadrupole MS coupled with an Ultimate 3000 UHPLC allowed multiple reaction monitoring detection, ensuring precise analyte quantification. The assay exhibited linear responses across a broad spectrum of concentrations: ranging from 1.64 to 1000 ng/mL for both FFA and CBD, and from 0.82 to 500 ng/mL for norFFA. The method proves accurate and reproducible, free from matrix effect. Additionally, FFA stability in plasma at 4 °C and -20 °C for up to 7 days bolsters its clinical applicability. Plasma concentrations detected in patients samples, expressed as mean ± standard deviation, were 0.36 ± 0.09 ng/mL for FFA, 19.67 ± 1.22 ng/mL for norFFA. This method stands as a robust tool for therapeutic drug monitoring (TDM) of FFA and CBD, offering significant utility in assessing drug-drug interactions in co-treated patients, thus contributing to optimized patient care in complex therapeutic scenarios.

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.

Titania-based fabric phase sorptive extraction approach for the determination of antiepileptic drugs, levetiracetam and lamotrigine in urine samples using high-performance liquid chromatography-photo diode array detection

A new fabric phase sorptive extraction (FPSE) based separation and enrichment method was developed for sensitive determination of two antiepileptic drug molecules, Levetiracetam (LEV) and Lamotrigine (LTG). The analysis of these drug molecules was performed with high-performance liquid chromatography equipped with photodiode array detector (HPLC-PDA) after FPSE. HPLC analysis was carried out by using phenyl hexyl column, under isocratic conditions with the mobile phase composed of pH 3.0 buffer-acetonitrile (77:23 v: v). All parameters affecting the separation and enrichment process were studied and optimized step by step. The linear working range of the developed method was calculated in the range of 10.0-1000.0 ng mL-1 for both the drug molecules (LEV and LTG). The limits of detection of the method (LODs) were calculated as 2.72 and 3.64 ng mL-1, respectively. The relative standard deviation (%RSD) values of the developed method as an indicator of precision were varied between 4.0 and 7.3. The accuracy of the optimized FPSE method was determined by the recovery tests utilizing spiked samples and results were assessed in the range from 94.6 to 106.3%. This is the first application of sol-gel Titania polycaprolactone-polydimethylsiloxane-polycaprolactone (Ti-PCAP-PDMS-PCAP) based FPSE membrane in the determination of antiepileptic drug molecules.

Efficacy of silver nanoparticles against Trichinella spiralis in mice and the role of multivitamin in alleviating its toxicity

Trichinellosis is a worldwide zoonotic disease. The majority of currently available anti-trichinellosis medications exhibit inadequate efficacy. The efficacy of a natively prepared new formulation of silver nanoparticles (Ag-NPs) was evaluated in the treatment of Trichinella spiralis (T. spiralis) infection in mice alone and combined with multivitamin-mineral (MM). After investigating the product's biological and pharmacological characteristics, its therapeutic dose was estimated to be Ag-NPs at 21.5 mg/kg B.W. This dose was orally inoculated to experimentally infected mice at 3-5 days post-inoculation (dpi) against the mature worms, at 8-10 dpi against the newborn larvae, and at 33-35th dpi against the encapsulated larvae. Each treatment's efficacy was assessed by scarifying control and treated mice 3 days post-treatment. The drug alone or in supplement form has a high trichinocidal effect exceeding that of the reference drug. Early treatment (3-5 dpi) by Ag-NPs or Ag-NPs + MM and albendazole revealed high efficacy against the intestinal stage, reaching 93.3%, 94.7%, and 90.6% for the three treatments, respectively. The materials causing a significant (P-value < 0.001) decrease in the mean encapsulated larvae reached 86.61%, 89.07%, and 88.84%/gm of muscles using the three treatments, respectively. Moreover, all larvae extracted from Ag-NPs-treated groups failed to induce infection post-inoculation in new mice. Additionally, combining the material with MM proved to overcome the reversible adverse effects of silver material on the estimated redox parameters and liver and kidney biomarkers, denoting its ability to alleviate Ag-NP toxicity. In conclusion, the high trichinocidal effect of Ag-NPs against the adult and encapsulated larvae during a short inoculation period introduced Ag-NPs as an alternative to other nematicidal drugs.

Topiramate dosage optimization for effective antiseizure management via population pharmacokinetic modeling

OBJECTIVE

Despite the suggested topiramate serum level of 5-20 mg/L, numerous institutions have observed substantial drug response at lower levels. We aim to investigate the correlation between topiramate serum levels, drug responsiveness, and adverse events to establish a more accurate and tailored therapeutic range.

METHODS

We retrospectively analyzed clinical data collected between January 2017 and January 2022 at Seoul National University Hospital. Drug responses to topiramate were categorized as "insufficient" or "sufficient" by reduction in seizure frequency ≥ 50%. A population pharmacokinetic model estimated serum levels from spot measurements. ROC curve analysis determined the optimal cutoff values.

RESULTS

A total of 389 epilepsy patients were reviewed having a mean dose of 178.4 ± 117.9 mg/day and the serum level, 3.9 ± 2.8 mg/L. Only 5.6% samples exhibited insufficient response, with a mean serum level of 3.6 ± 2.5 mg/L while 94.4% demonstrated sufficient response, with a mean 4.0 ± 2.8 mg/L, having no statistical significance. Among the 69 reported adverse events, logistic regression analysis identified a significant association between ataxia and serum concentration (p = 0.04), with an optimal cutoff value of 6.5 mg/L.

INTERPRETATION

This study proposed an optimal therapeutic concentration for topiramate based on patients' responsiveness to the drug and the incidence of adverse effects. We recommended serum levels below 6.5 mg/L to mitigate the risk of ataxia-related side effects while dose elevation was found unnecessary for suboptimal responders, as the drug's effectiveness plateaus at minimal doses.

Anti-seizure Medications: Challenges and Opportunities

Epilepsy is a chronic neurological condition characterized by unprovoked, recurrent seizures. There are several types of epilepsy, and the cause of the condition can vary. Some cases of epilepsy have a genetic component, while others may be caused by brain injuries, infections, or other underlying conditions. Treatment for epilepsy typically involves anti-seizure medications (ASMs), although different approaches, such as surgery or a special diet, may be considered in specific cases. The treatment aims to effectively manage and potentially eliminate seizures while minimizing any accompanying side effects. Many different ASMs are available, and the choice of medication depends on several factors, including the type of seizures, the patient's age, general health, and potential drug interactions. For the treatment of epilepsy, there have been significant advancements in recent decades, which have led to the approval of many different ASMs. Newer ASMs offer a broader range of mechanisms of action, improved tolerability profiles, and reduced drug interactions compared to older drugs. This review aims to discuss the pharmacological characteristics, clinical applications, effectiveness, and safety of ASMs, with a particular emphasis on various age groups, especially children. Moreover, this review seeks to provide a comprehensive understanding of ASM therapy for epilepsy management, assisting physicians in selecting suitable ASMs for their patients.

E2730, an uncompetitive γ-aminobutyric acid transporter-1 inhibitor, suppresses epileptic seizures in a rat model of chronic mesial temporal lobe epilepsy

OBJECTIVE

More than one third of mesial temporal lobe epilepsy (MTLE) patients are resistant to current antiseizure medications (ASMs), and half experience mild-to-moderate adverse effects of ASMs. There is therefore a strong need to develop and test novel ASMs. The objective of this work is to evaluate the pharmacokinetics and neurological toxicity of E2730, a novel uncompetitive inhibitor of γ-aminobutyric acid transporter-1, and to test its seizure suppression effects in a rat model of chronic MTLE.

METHODS

We first examined plasma levels and adverse neurological effects of E2730 in healthy Wistar rats. Adult male rats were implanted with osmotic pumps delivering either 10, 20, or 100 mg/kg/day of E2730 subcutaneously for 1 week. Blood sampling and behavioral assessments were performed at several timepoints. We next examined whether E2730 suppressed seizures in rats with chronic MTLE. These rats were exposed to kainic acid-induced status epilepticus, and 9 weeks later, when chronic epilepsy was established, were assigned to receive one of the three doses of E2730 or vehicle for 1 week in a randomized crossover design. Continuous video-electroencephalographic monitoring was acquired during the treatment period to evaluate epileptic seizures.

RESULTS

Plasma levels following continuous infusion of E2730 showed a clear dose-related increase in concentration. The drug was well tolerated at all doses, and any sedation or neuromotor impairment was mild and transient, resolving within 48 h of treatment initiation. Remarkably, E2730 treatment in chronically epileptic rats led to seizure suppression in a dose-dependent manner, with 65% of rats becoming seizure-free at the highest dose tested. Mean seizure class did not differ between the treatment groups.

SIGNIFICANCE

This study shows that continuous subcutaneous infusion of E2730 over 7 days results in a marked, dose-dependent suppression of spontaneous recurrent seizures, with minimal adverse neurological effects, in a rat model of chronic MTLE. E2730 shows strong promise as an effective new ASM to be translated into clinical trials.

Effects of valproic acid on syncytialization in human placental trophoblast cell lines

The placenta is a critical organ for fetal development and a healthy pregnancy, and has multifaceted functions (e.g., substance exchange and hormone secretion). Syncytialization of trophoblasts is important for maintaining placental functions. Epilepsy is one of the most common neurological conditions worldwide. Therefore, this study aimed to reveal the influence of antiepileptic drugs, including valproic acid (VPA), carbamazepine, lamotrigine, gabapentin, levetiracetam, topiramate, lacosamide, and clobazam, at clinically relevant concentrations on syncytialization using in vitro models of trophoblasts. To induce differentiation into syncytiotrophoblast-like cells, BeWo cells were treated with forskolin. Exposure to VPA was found to dose-dependently influence syncytialization-associated genes (ERVW-1, ERVFRD-1, GJA1, CGB, CSH, SLC1A5, and ABCC4) in differentiated BeWo cells. Herein, the biomarkers between differentiated BeWo cells and the human trophoblast stem model (TSCT) were compared. In particular, MFSD2A levels were low in BeWo cells but abundant in TSCT cells. VPA exposure affected the expression of ERVW-1, ERVFRD-1, GJA1, CSH, MFSD2A, and ABCC4 in differentiated cells (ST-TSCT). Furthermore, VPA exposure attenuated BeWo and TSCT cell fusion. Finally, the relationships between neonatal/placental parameters and the expression of syncytialization markers in human term placentas were analyzed. MFSD2A expression was positively correlated with neonatal body weight, head circumference, chest circumference, and placental weight. Our findings have important implications for better understanding the mechanisms of toxicity of antiepileptic drugs and predicting the risks to placental and fetal development.

A Novel Approach for Therapeutic Drug Monitoring of Valproic Acid Using FT-IR Spectroscopy and Nonlinear Support Vector Regression

BACKGROUND

Recent technological progress has bolstered efforts to bring personalized medicine from theory into clinical practice. However, progress in areas such as therapeutic drug monitoring (TDM) has remained somewhat stagnant. In drugs with well-known dose-response relationships, TDM can enhance patient outcomes and reduce health care costs. Traditional monitoring methods such as chromatography-based or immunoassay techniques are limited by their higher costs and slow turnaround times, making them unsuitable for real-time or onsite analysis.

OBJECTIVE

In this work, we propose the use of a fast, direct, and simple approach using Fourier transform infrared spectroscopy (FT-IR) combined with chemometric techniques for the therapeutic monitoring of valproic acid (VPA).

METHOD

In this context, a database of FT-IR spectra was constructed from human plasma samples containing various concentrations of VPA; these samples were characterized by the reference method (immunoassay technique) to determine the VPA contents. The FT-IR spectra were processed by two chemometric regression methods: partial least-squares regression (PLS) and support vector regression (SVR).

RESULTS

The results provide good evidence for the effectiveness of the combination of FT-IR spectroscopy and SVR modeling for estimating VPA in human plasma. SVR models showed better predictive abilities than PLS models in terms of root-mean-square error of calibration and prediction RMSEC, RMSEP, R2Cal, R2Pred, and residual predictive deviation (RPD).

CONCLUSIONS

This analytical tool offers potential for real-time TDM in the clinical setting.

HIGHLIGHTS

FTIR spectroscopy was evaluated for the first time to predict VPA in human plasma for TDM. Two regressions were evaluated to predict VPA in human plasma, and the best-performing model was obtained using nonlinear SVR.

Revolutionizing Precision Medicine: Exploring Wearable Sensors for Therapeutic Drug Monitoring and Personalized Therapy

Precision medicine, particularly therapeutic drug monitoring (TDM), is essential for optimizing drug dosage and minimizing toxicity. However, current TDM methods have limitations, including the need for skilled operators, patient discomfort, and the inability to monitor dynamic drug level changes. In recent years, wearable sensors have emerged as a promising solution for drug monitoring. These sensors offer real-time and continuous measurement of drug concentrations in biofluids, enabling personalized medicine and reducing the risk of toxicity. This review provides an overview of drugs detectable by wearable sensors and explores biosensing technologies that can enable drug monitoring in the future. It presents a comparative analysis of multiple biosensing technologies and evaluates their strengths and limitations for integration into wearable detection systems. The promising capabilities of wearable sensors for real-time and continuous drug monitoring offer revolutionary advancements in diagnostic tools, supporting personalized medicine and optimal therapeutic effects. Wearable sensors are poised to become essential components of healthcare systems, catering to the diverse needs of patients and reducing healthcare costs.

Nose-to-brain delivery of perampanel formulated in a self-microemulsifying drug delivery system improves anticonvulsant and anxiolytic activity in mice

Perampanel (PER) is a potent third-generation antiepileptic drug only available for oral administration. Additionally, PER has shown potential in managing epilepsy comorbidities such as anxiety. Previously, we demonstrated that the intranasal (IN) administration of PER, loaded in a self-microemulsifying drug delivery system (SMEDDS), improved brain-targeting and exposure in mice. Herein, we investigated PER brain biodistribution, its anticonvulsant and anxiolytic effects, and its potential olfactory and neuromotor toxicity after IN administration to mice (1 mg/kg). PER showed a rostral-caudal brain biodistribution pattern when administered intranasally. At short times post-nasal dosing, high PER concentrations were found in olfactory bulbs (olfactory bulbs/plasma ratios of 1.266 ± 0.183 and 0.181 ± 0.027 after IN and intravenous administrations, respectively), suggesting that a fraction of the drug directly reaches brain through the olfactory pathway. In maximal electroshock seizure test, IN PER protected 60% of mice against seizure development, a substantially higher value than the 20% protected after receiving oral PER. . PER also demonstrated anxiolytic effects in open field and elevated plus maze tests. Buried food-seeking test showed no signs of olfactory toxicity. Neuromotor impairment was found in rotarod and open field tests at the times of PER maximum concentrations after IN and oral administrations. Nevertheless, neuromotor performance was improved after repeated administrations. Compared with IN vehicle, PER IN administration decreased brain levels of L-glutamate (0.91 ± 0.13 mg/mL vs 0.64 ± 0.12 mg/mL) and nitric oxide (100 ± 15.62% vs 56.62 ± 4.95%), without interfering in GABA levels. Altogether, these results suggest that the IN PER delivery through the developed SMEDDS can be a safe and promising alternative to oral treatment, which support the design of clinical studies to evaluate the IN PER delivery to treat epilepsy and neurological-related conditions as anxiety.

Population Pharmacokinetic Analysis of Perampanel in Portuguese Patients Diagnosed with Refractory Epilepsy

Perampanel is a promising antiepileptic drug (AED) for refractory epilepsy treatment due to its innovative mechanism of action. This study aimed to develop a population pharmacokinetic (PopPK) model to be further used in initial dose optimization of perampanel in patients diagnosed with refractory epilepsy. A total of seventy-two plasma concentrations of perampanel obtained from forty-four patients were analyzed through a population pharmacokinetic approach by means of nonlinear mixed effects modeling (NONMEM). A one-compartment model with first-order elimination best described the pharmacokinetic profiles of perampanel. Interpatient variability (IPV) was entered on clearance (CL), while the residual error (RE) was modeled as proportional. The presence of enzyme-inducing AEDs (EIAEDs) and body mass index (BMI) were found as significant covariates for CL and volume of distribution (V), respectively. The mean (relative standard error) estimates for CL and V of the final model were 0.419 L/h (5.56%) and 29.50 (6.41%), respectively. IPV was 30.84% and the proportional RE was 6.44%. Internal validation demonstrated an acceptable predictive performance of the final model. A reliable population pharmacokinetic model was successfully developed, and it is the first enrolling real-life adults diagnosed with refractory epilepsy.

The Antiepileptic Drug Oxcarbazepine Inhibits the Growth of Patient-Derived Isocitrate Dehydrogenase Mutant Glioma Stem-like Cells

Patients diagnosed with isocitrate dehydrogenase mutant (IDH^mut) gliomas suffer frequently from seizures. Although the clinical course is less aggressive than that of its IDH wildtype counterpart, recent discoveries have shown that epileptic activity can promote tumor proliferation. However, it is not known if antiepileptic drugs confer additional value by inhibiting tumor growth. In this study, the antineoplastic properties of 20 FDA-approved antiepileptic drugs (AEDs) were tested in six patient-derived IDH^mut glioma stem-like cells (GSCs). Cell proliferation was assessed using the CellTiterGlo-3D assay. Two of the screened drugs (oxcarbazepine and perampanel) demonstrated an antiproliferative effect. A subsequent eight-point dose-response curve proved the dose-dependent growth inhibition for both drugs, but only oxcarbazepine reached an IC₅₀ value below 100 µM in 5/6 GSCs (mean 44.7 µM; range 17.4-98.0 µM), approximating the possible c_max for oxcarbazepine in patient serums. Furthermore, the treated GSC spheroids were 82% smaller (mean volume 1.6 nL vs. 8.7 nL; p = 0.01 (live/dead^TM fluorescence staining)), and the apoptotic events increased by more than 50% (caspase-3/7 activity; p = 0.006). Taken together, this drug screen of a large series of antiepileptic drugs identified oxcarbazepine as a potent proapoptotic drug in IDH^mut GSCs, which combines antiepileptic and antineoplastic properties to treat this seizure-prone patient population.

Intravenous topiramate for seizure emergencies - First in human case report

Topiramate (TPM) is widely used in focal and generalized epilepsies. It is commercially available as tablets and sprinkles capsules for oral treatment. Previous studies comparing intravenous (IV) to oral TPM in healthy adults showed more rapid pharmacodynamic effects in cases of IV administration. Despite promising findings, no clinical application in humans followed. We present a case of a pregnant woman with idiopathic generalized epilepsy who experienced a generalized tonic-clonic seizure in the third trimenon due to low TPM levels attributed to pregnancy followed by repeated prolonged absences. We applied a new meglumine-based solution (1%) of TPM (10 mg/ml) in two IV infusions of 200 mg each under EEG monitoring over a total duration of 1 hour. The infusion was well tolerated and led to a rapid increase in plasma TPM levels. A clinical as well as electroencephalographic improvement was documented within the first hours. To the best available knowledge, this is the first reported case where IV TPM was used therapeutically for seizure treatment in humans. It is also the first time that the new meglumine-based solution was used in a human with epilepsy. The advantages of IV route delivery and the solution's quick preparation, high tolerability, and low toxicity make it ideal for use in many clinical settings and high-care patients. IV TPM seems to be a reasonable adjunctive option for adults with seizures, previously stabilized on oral TPM, who need rapid plasma concentration boosting. Although our experience was successful in using injectable TPM in seizure emergencies, randomized controlled clinical trials are required to make recommendations for the use of IV TPM on patients with epilepsy. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022 in Salzburg, Austria.

The Anti-Epileptic Drugs Lamotrigine and Valproic Acid Reduce the Cardiac Sodium Current

Anti-epileptic drugs (AEDs) are associated with increased risk of sudden cardiac death. To establish whether gabapentin, lamotrigine, levetiracetam, pregabalin, and valproic acid reduce the Na_v1.5 current, we conducted whole-cell patch-clamp studies to study the effects of the five AEDs on currents of human cardiac Na_v1.5 channels stably expressed in HEK293 cells, and on action potential (AP) properties of freshly isolated rabbit ventricular cardiomyocytes. Lamotrigine and valproic acid exhibited inhibitory effects on the Na_v1.5 current in a concentration-dependent manner with an IC₅₀ of 142 ± 36 and 2022 ± 25 µM for lamotrigine and valproic acid, respectively. In addition, these drugs caused a hyperpolarizing shift of steady-state inactivation and a delay in recovery from inactivation. The changes on the Na_v1.5 properties were reflected by a reduction in AP upstroke velocity (43.0 ± 6.8% (lamotrigine) and 23.7 ± 10.6% (valproic acid) at 1 Hz) and AP amplitude; in contrast, AP duration was not changed. Gabapentin, levetiracetam, and pregabalin had no effect on the Na_v1.5 current. Lamotrigine and valproic acid reduce the Na_v1.5 current density and affect its gating properties, resulting in a decrease of the AP upstroke velocity. Gabapentin, levetiracetam, and pregabalin have no effects on the Na_v1.5 current.

A simple and easy non-derivatization gas chromatography-mass spectrometry method for simultaneous quantification of valproic acid, gabapentin, pregabalin, and vigabatrin in human plasma

Immunoassays are currently not available in commercial kits for the quantification of valproic acid, vigabatrin, pregabalin, and gabapentin, which also cannot suffer the limitations of interferences of substances with similar structures. Chromatography is a good alternative to immunoassay. In this study, a simple and robust non-derivatization gas chromatography-mass spectrometry method for simultaneous determination of the above four drugs in human plasma was developed and validated for therapeutic drug monitoring purposes. This method employed benzoic acid as the internal standard with hydrochloric acid for plasma acidification and ACN for precipitate protein. The supernatant was directly injected into gas chromatography-mass spectrometry for analysis. Good linearity was obtained with linear correlation coefficients of the four analytes of 0.9988-0.9996. Extraction recoveries of valproic acid, vigabatrin, pregabalin, and gabapentin were respectively in the ranges of 91.3%-94.5%, 90.0%-90.9%, 90.0%-92.1%, and 88.0%-92.2% with the relative standard deviation values less than 12.6%. Intra- and inter-batch precision and accuracy, and stability assays were all acceptable. Taken together, the novel method developed in this study provided easy plasma pretreatment, good extraction yield, and high chromatographic resolution, which has been successfully validated through the quantification of valproic acid in the plasma of 46 patients with epilepsy.

The protective effects of topiramate and spirulina against doxorubicin-induced cardiotoxicity in rats

Doxorubicin (DOX) is a widely used chemotherapy drug that can cause significant cardiotoxicity, limiting its clinical application. This study aimed to investigate the potential protective effects of topiramate (TPM) and spirulina (SP), either alone or in combination, in preventing DOX-induced cardiotoxicity. Adult Sprague Dawley rats were divided into five groups, including a normal control group and groups receiving DOX alone, DOX with TPM, DOX with SP, or DOX with a combination of TPM and SP. Cardiotoxicity was induced by administering DOX intraperitoneally at a cumulative dose of 16 mg/kg over 4 weeks. TPM and/or SP administration started 1 week before DOX treatment and continued for 35 days. Body weight, serum markers of cardiac damage, oxidative stress and inflammatory parameters were assessed. Histopathological and immunohistochemical examinations were performed on cardiac tissues. Results showed that TPM and SP monotherapy led to significant improvements in serum levels of cardiac markers, decreased oxidative stress, reduced fibrosis-related growth factor levels, increased antioxidant levels, and improved histopathological features. SP demonstrated more prominent effects in comparison to TPM, and the combination of TPM and SP exhibited even more pronounced effects. In conclusion, TPM and SP, either alone or in combination, hold promise as therapeutic interventions for mitigating DOX-induced cardiotoxicity.

Evaluation of a Capillary Microsampling Device for Analyzing Plasma Lenvatinib Concentration in Patients With Hepatocellular Carcinoma

BACKGROUND

The anticancer drug, Lenvima (lenvatinib), has severe side effects. Therapeutic drug monitoring helps ensure its efficacy and safety. Regular and optimally timed blood sampling is tough, especially when lenvatinib is self-medicated. Microsampling using the easy to handle Microsampling Wing (MSW) may help circumvent this problem. However, current lenvatinib detection methods are not sensitive enough to detect its concentrations in microsamples (<50-250 μL). Thus, the aim of this study was 2-fold (1) develop an analytic method to estimate plasma lenvatinib concentrations in microsamples and (2) verify whether this method works on micro (5.6 μL) blood plasma samples obtained clinically through MSW from patients with unresectable hepatocellular carcinoma (HCC).

METHODS

A simple, highly sensitive, and specific liquid chromatography-electrospray ionization tandem mass spectrometry method was developed. Using this novel protocol, the trough blood plasma concentration of lenvatinib was measured for both blood sampled conventionally and that using MSW. Thirty-five venous whole blood samples were obtained from 11 patients with HCC. Furthermore, the stability of lenvatinib in MSW samples during storage was evaluated.

RESULTS

The mean plasma lenvatinib concentration estimates were not significantly different between the MSW and conventional venous blood samples. CV for interday and intraday assays was low. Up to day 5, the lenvatinib concentration in the MSW samples was 85%-115% of the initial day concentration (when stored at 25°C or 4°C). The interference of endogenous matrix components in the human plasma was low.

CONCLUSIONS

These results indicate that the novel mass spectrometry protocol accurately measures lenvatinib in human plasma and is reproducible. Thus, MSW could be a useful microsampling device for lenvatinib therapeutic drug monitoring in patients with HCC when used in combination with this novel liquid chromatography-electrospray ionization tandem mass spectrometry detection method.

Management of anti-seizure medications in lactating women with epilepsy

Epilepsy is a common neurological disease. At present, there are about 70 million epilepsy patients in the world, half of them are women, and 30-40% of women with epilepsy are of childbearing potential. Patients with epilepsy who are of childbearing potential face more challenges, such as seizures caused by hormonal fluctuations and the risk of adverse effects on the mother and baby from taking anti-seizure medications (ASMs). Breast milk is one of the best gifts that a mother can give her baby, and breastfeeding can bring more benefits to the baby. Compared with healthy people, people with epilepsy have more concerns about breastfeeding because they are worried that ASMs in their milk will affect the growth and development of the baby, and they are always faced with the dilemma of whether to breastfeed after childbirth. Regarding, whether women with epilepsy can breastfeed while taking ASMs, and whether breastfeeding will adversely affect the baby is still an important topic of concern for patients and doctors. This article reviews the existing research on breastfeeding-related issues in women with epilepsy to guide clinical practice, and improve the breastfeeding compliance of women with epilepsy.

Development and Validation of a UHPLC-MS/MS-Based Method to Quantify Cenobamate in Human Plasma Samples

Cenobamate (CNB) is the newest antiseizure medication (ASM) approved by the FDA in 2019 to reduce uncontrolled partial-onset seizures in adult patients. Marketed as Xcopri in the USA or Ontozry in the EU (tablets), its mechanism of action has not been fully understood yet; however, it is known that it inhibits voltage-gated sodium channels and positively modulates the aminobutyric acid (GABA) ion channel. CNB shows 88% of oral bioavailability and is responsible for modifying the plasma concentrations of other co-administered ASMs, such as lamotrigine, carbamazepine, phenytoin, phenobarbital and the active metabolite of clobazam. It also interferes with CYP2B6 and CYP3A substrates. Nowadays, few methods are reported in the literature to quantify CNB in human plasma. The aim of this study was to develop and validate, according to the most recent guidelines, an analytical method using ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) to evaluate CNB dosage in plasma samples. Furthermore, we provided a preliminary clinical application of our methodology by evaluating the pharmacokinetic parameters of CNB in two non-adult patients. Plasma levels were monitored for two months. Preliminary data showed a linear increase in plasma CNB concentrations, in both patients, in agreement with the increase in CNB dosage. A seizure-free state was reported for both patients at the dose of 150 mg per day.

Therapeutic drug monitoring of perampanel in children diagnosed with epilepsy: Focus on influencing factors on the plasma concentration-to-dose ratio

OBJECTIVE

This study aimed to investigate the efficacy and tolerability of perampanel (PER) therapy and to optimize a specific plasma reference range for PER in children. Another major aim was to evaluate the potential determinators of PER concentration.

METHODS

Concentrations obtained from 80 children were analyzed for routine therapeutic drug monitoring (TDM) between 2021 and 2022. We retrospectively reviewed the clinical data of these patients and assessed the efficacy at 3 months after treatment initiation. Trough concentration-to-dose ratio (C₀ /Dose ratio) of PER was compared among patients on various potential influencing factors.

RESULTS

A 3-month PER therapy produced a ≥50% reduction in seizure frequency in 58.8% of patients. Twelve patients reported at least one adverse effect (AE), mainly dizziness. The monitoring data showed that the median C₀ was 325.5 ng/mL. Under maintenance dosages, approximately 75% of the C₀ values were 180.0-610.0 ng/mL. The C₀ /Dose ratio in patients aged 1 to <4 was significantly lower by twofold than in those aged 4 to ≤12 years (P = 0.001). Enzyme-inducing ASMs (EIASMs) decreased the C₀ /Dose ratio of PER by 25.9% (P = 0.165). In addition, seizure frequency reduction in responders was achieved at a median PER C₀ value of 357 ng/mL, which was similar to the value of 314 ng/mL found in nonresponders (P = 0.288). No significant difference was found in PER C₀ values between patients with and without AEs (P = 0.082).

SIGNIFICANCE

In this study, PER treatment showed acceptable efficacy and tolerance in Chinese children with epilepsy. Contributing factors like age to variable C₀ /Dose ratios were identified, and complex PER-ASMs interactions were observed. Notably, the reference range, that is, 180.0-610.0 ng/mL, for routine PER monitoring may be more applicable for them. Routine TDM should be considered a positive attempt to manage the effectiveness and safety of PER.

Development and application of a novel LC-MS-MS method for human plasma concentration monitoring of perampanel in pediatric epilepsy patients

This study has developed and validated a novel LC-MS/MS assay method to quantify perampanel in pediatric patients with epilepsy in Xinjiang, China. Our assay reduces current specimen volume requirements, and decreases the turnaround time for results. Samples were separated by gradient elution and then injected into the mass spectrometer with a total run-time of 3 min per sample. Detection of ions from the analytes was conducted using multiple reactions by monitoring transitions of m/z 350.2-m/z 219.0 for perampanel and m/z 359.1-m/z 323.1 for IS, as precursor ion and product one, respectively. The peak area ratios of perampanel with IS within the plasma samples were linear in the concentration range of 0.1-3.2 μg/mL (y = 2.87 x + 0.61; r ² ≥ 0.99). The within-run and between-run precision coefficient of variation (CV (%) did not exceed 11.03%, and the accuracy (bias) ranged from -1.07% to 6.69%. The mean absolute recoveries of perampanel for four QC levels (including LLOQ, LQC, MQC and HQC) determined by this method were 87.69%, 94.04%, 107.50% and 95.15%, respectively. The stability results for this method showed that the plasma samples of perampanel were stable under all tested conditions (86.43-104.81%), with % CV maximum of 8.74%.

Treatment and care of women with epilepsy before, during, and after pregnancy: a practical guide

Women with epilepsy (WWE) wishing for a child represent a highly relevant subgroup of epilepsy patients. The treating epileptologist needs to delineate the epilepsy syndrome and choose the appropriate anti-seizure medication (ASM) considering the main goal of seizure freedom, teratogenic risks, changes in drug metabolism during pregnancy and postpartum, demanding for up-titration during and down-titration after pregnancy. Folic acid or vitamin K supplements and breastfeeding are also discussed in this review. Lamotrigine and levetiracetam have the lowest teratogenic potential. Data on teratogenic risks are also favorable for oxcarbazepine, whereas topiramate tends to have an unfavorable profile. Valproate needs special emphasis. It is most effective in generalized seizures but should be avoided whenever possible due to its teratogenic effects and the negative impact on neuropsychological development of in utero-exposed children. Valproate still has its justification in patients not achieving seizure freedom with other ASMs or if a woman decides to or cannot become pregnant for any reason. When valproate is the most appropriate treatment option, the patient and caregiver must be fully informed of the risks associated with its use during pregnancies. Folate supplementation is recommended to reduce the risk of major congenital malformations. However, there is insufficient information to address the optimal dose and it is unclear whether higher doses offer greater protection. There is currently no general recommendation for a peripartum vitamin K prophylaxis. During pregnancy most ASMs (e.g. lamotrigine, oxcarbazepine, and levetiracetam) need to be increased to compensate for the decline in serum levels; exceptions are valproate and carbamazepine. Postpartum, baseline levels are reached relatively fast, and down-titration is performed empirically. Many ASMs in monotherapy are (moderately) safe for breastfeeding and women should be encouraged to do so. This review provides a practically oriented overview of the complex management of WWE before, during, and after pregnancy.

Serum monitoring of carbamazepine in patients with epilepsy and clinical implications

Carbamazepine is a drug with a narrow therapeutic range that requires clinical monitoring, since its toxic effects are not easily predictable, and the therapeutic level can vary. Our study aimed to monitor the serum level and determine the concentration/dose relationship of carbamazepine in people with epilepsy, analyzing its clinical implication. It is observed that 90.48% of the study volunteers present serum level values (4.3–10.4 mg/L) within the therapeutic range (4–12 mg/L); 7.14% present supratherapeutic levels (12.7–14.4 mg/L), 2.38% subtherapeutic (0.93 mg/L). The findings indicate a negative correlation (r = -0.616; r2 = 0.379; p = 0.001), between the dose (mg/day) and the dose ratio (mg/L/mg/day); and a positive correlation (r = 0.544; r2 = 0.296; p = 0.002), between the dose (mg/day)-serum concentration (mg/L). ANOVA and Tukey’s test mean difference is significant (p&lt;0.05). It is concluded that there is a positive and significant linear correlation between daily doses and serum carbamazepine concentrations, which should be considered to individualize the dose and optimize clinical results.

Development and evaluation of a simple and easy HPLC-UV system simultaneously suitable for determination of 24 anti-epileptic drugs in plasma

This paper aims to establish a simple and easy HPLC system coupled with UV detector suitable for simultaneous determination of 24 antiepileptic drugs in human plasma. Optimized chromatographic separation was performed on a ZORBAX Eclipse Plus-C18 (4.6 mm×150 mm, 3.5 μm) column with acetonitrile and 5 mM potassium dihydrogen phosphate water solution as mobile phase. 24 antiepileptic drugs were divided into three groups and eluted with different gradient procedures, respectively. The column temperature was maintained at 35 °C and the detection wavelength was set at 210 nm. Plasma was processed with ethyl acetate or acetonitrile. The calibration curves of 24 antiepileptic drugs demonstrated good linearity within the test range (r > 0.996). The intra- and inter-batch precision and accuracy were all less than 15%, while extraction recoveries were in the range of 74.57%∼90.89% with the RSD values less than 15%. The validated methods have been successfully applied to determination of some antiepileptic drugs in rat or patient plasma. Those results indicated that the developed methods were simple and easy, and could be suitable for the determination of 24 antiepileptic drugs in plasma just by changing the gradient elution procedures of mobile phase. This article is protected by copyright. All rights reserved.

Individualizing doses of antiepileptic drugs

INTRODUCTION

This review aims to identify the optimal therapeutic dosage of anti-epileptic drugs in terms of efficacy and safety in patients with multiple comorbidities.

AREAS COVERED

We have analyzed changes in terms of pharmacokinetics and pharmacodynamics of Brivaracetam, Carbamazepine, Lacosamide, Lamotrigine, Levetiracetam, Topiramate, Valproate, and Zonisamide in liver disease, chronic kidney disease, and in patients admitted to intensive care unit. Our literature search covers the past 5 years. We used PubMed, Google Scholar, and EMBASE database's to support our article.

EXPERT OPINION

To ensure that the patient with seizure receives the best treatment in relation to their comorbidities, careful clinical-laboratory monitoring is necessary to maximize effectiveness while maintaining safety, especially in the case of polytherapy.

The Pharmacokinetics of Levetiracetam in Critically Ill Adult Patients: An Intensive Care Unit Clinical Study

The aim of this study was to investigate levetiracetam pharmacokinetics in critically ill adult intensive care patients and to identify pathophysiological factors affecting its kinetics. Fourteen critically ill patients in an intensive care unit were enrolled in the study and received intravenous levetiracetam. Blood samples were collected at specific time points to determine the levetiracetam pharmacokinetics. Patient characteristics such as renal function, demographics, disease severity, organ dysfunction, and biochemical laboratory tests were evaluated for their influence on the kinetics of levetiracetam. Estimated glomerular filtration rate (eGFR) had a statistically significant (p = 0.001) effect on levetiracetam clearance. None of the other patient characteristics had a statistically significant effect on the pharmacokinetics. Simulations of dosing regimens revealed that even typically administered doses of levetiracetam may result in significantly increased concentrations and risk of drug toxicity in patients with impaired renal function. The Acute Physiology and Chronic Health Evaluation II (APACHE II) score differed significantly among the three groups with different epileptic activity (p = 0.034). The same groups also differed in terms of renal function (p = 0.031). Renal dysfunction should be considered when designing levetiracetam dosage. Patients with a low APACHE II score had the lowest risk of experiencing epileptic seizures.

Increased amisulpride serum concentration in a patient treated with concomitant pregabalin and trazodone: a case report

We report on the case of a 46-year-old woman with generalized anxiety disorder, paranoid personality disorder, and mild reduction in glomerular filtration rate (GFR). She was treated with pregabalin, trazodone, hydroxyzine, and clonazepam before hospital admission. Pharmacotherapy for the patient was changed during her first week in the hospital. Dosing of hydroxyzine and clonazepam was gradually decreased, and then these two drugs were withdrawn. Treatment with amisulpride was started on the fourth day after admission, and amisulpride serum levels were then measured three times as a part of therapeutic drug monitoring (TDM). The serum concentration of amisulpride detected during concurrent use of trazodone and pregabalin was approximately twice the therapeutic range for amisulpride. When the dose of pregabalin was reduced by half, the serum concentration of amisulpride decreased to therapeutic serum levels. We hypothesize that an interaction between amisulpride and pregabalin was responsible for the increased amisulpride concentration since both drugs are almost exclusively excreted from the body by the renal route. Pregabalin-amisulpride interaction might also be influenced by concomitant therapy with trazodone or a mild reduction in GFR. However, we only have clinical evidence for an interaction between amisulpride and pregabalin because after we halved the dose of pregabalin, the amisulpride concentration decreased, and the C/D ratio normalized. This could be helpful information for psychiatrists in order to avoid drug-drug interactions between amisulpride and pregabalin. We recommend TDM of amisulpride in patients treated concomitantly with other drugs eliminated mainly by the kidneys.

Ion-Channel Antiepileptic Drugs: An Analytical Perspective on the Therapeutic Drug Monitoring (TDM) of Ezogabine, Lacosamide, and Zonisamide

The term seizures includes a wide array of different disorders with variable etiology, which currently represent one of the most important classes of neurological illnesses. As a consequence, many different antiepileptic drugs (AEDs) are currently available, exploiting different activity mechanisms and providing different levels of performance in terms of selectivity, safety, and efficacy. AEDs are currently among the psychoactive drugs most frequently involved in therapeutic drug monitoring (TDM) practices. Thus, the plasma levels of AEDs and their metabolites are monitored and correlated to administered doses, therapeutic efficacy, side effects, and toxic effects. As for any analytical endeavour, the quality of plasma concentration data is only as good as the analytical method allows. In this review, the main techniques and methods are described, suitable for the TDM of three AEDs belonging to the class of ion channel agents: ezogabine (or retigabine), lacosamide, and zonisamide. In addition to this analytical overview, data are provided, pertaining to two of the most important use cases for the TDM of antiepileptics: drug–drug interactions and neuroprotection activity studies. This review contains 146 references.

Utility, promise, and limitations of liquid chromatography-mass spectrometry-based therapeutic drug monitoring in precision medicine

Therapeutic drug monitoring (TDM) is typically referred to as the measurement of the concentration of drugs in patient blood. Although in the past, TDM was restricted to drugs with a narrow therapeutic range in order to avoid drug toxicity, TDM has recently become a major tool for precision medicine being applied to many more drugs. Through compensating for interindividual differences in a drug's pharmacokinetics, improved dosing of individual patients based on TDM ensures maximum drug effectiveness while minimizing side effects. This is especially relevant for individuals that present a particularly high intervariability in pharmacokinetics, such as newborns, or for critically/severely ill patients. In this article, we will review the applications for and limitations of TDM, discuss for which patients TDM is most beneficial and why, examine which techniques are being used for TDM, and demonstrate how mass spectrometry is increasingly becoming a reliable and convenient alternative for the TDM of different classes of drugs. We will also highlight the advances, challenges, and limitations of the existing repertoire of TDM methods and discuss future opportunities for TDM-based precision medicine.

Pharmacokinetic variability of eslicarbazepine in real clinical practice

INTRODUCTION

Eslicarbazepine acetate (ESL) is a sodium channel blocker indicated for partial-onset seizures with or without secondary generalization, at a single daily dose. There are very few publications on the levels of ESL metabolites in real clinical practice.

OBJECTIVE

To describe the serum levels of licarbazepine (main metabolite of ESL) in patients with refractory epilepsy in real clinical practice. To evaluate the influence of age, sex, and polytherapy on levels and adverse effects.

METHODS

This study involved a retrospective analysis of patients diagnosed with epilepsy treated with ESL for whom plasma levels of licarbazepine were available, measured by spectrophotometry.

RESULTS

Sixty-four patients were included. One patient had licarbazepine levels of 0 (admitted not taking the drug) was not analyzed. Mean licarbazepine levels of 7.66 µg/mL (400 mg/day dose), 16.56 µg/mL (800-mg dose), and 20.80 µg/mL (1200 mg) were significantly different. There was a significant correlation between daily dose and serum levels (p < 0.05) and between the concentration/dose ratio and lower to higher doses (p < 0.05). Pharmacokinetic variability (coefficient of variation for the concentration/dose ratio) was 33.2%. We found a decrease in the concentration/dose ratio in the 1200 mg/day dose, compared to lower doses. We did not find differences by sex or intake of other antiepileptic inducers or metabolic inhibitors. Fifteen patients (23.8%) had mild nonsymptomatic hyponatremia.

CONCLUSION

These results suggest that it is not necessary to routinely determine licarbazepine levels. In specific cases, licarbazepine levels can be useful to assess adherence to treatment and for personalized dose adjustment.

Pharmacokinetic Drug-Drug Interactions among Antiepileptic Drugs, Including CBD, Drugs Used to Treat COVID-19 and Nutrients

Anti-epileptic drugs (AEDs) are an important group of drugs of several generations, ranging from the oldest phenobarbital (1912) to the most recent cenobamate (2019). Cannabidiol (CBD) is increasingly used to treat epilepsy. The outbreak of the SARS-CoV-2 pandemic in 2019 created new challenges in the effective treatment of epilepsy in COVID-19 patients. The purpose of this review is to present data from the last few years on drug–drug interactions among of AEDs, as well as AEDs with other drugs, nutrients and food. Literature data was collected mainly in PubMed, as well as google base. The most important pharmacokinetic parameters of the chosen 29 AEDs, mechanism of action and clinical application, as well as their biotransformation, are presented. We pay a special attention to the new potential interactions of the applied first-generation AEDs (carbamazepine, oxcarbazepine, phenytoin, phenobarbital and primidone), on decreased concentration of some medications (atazanavir and remdesivir), or their compositions (darunavir/cobicistat and lopinavir/ritonavir) used in the treatment of COVID-19 patients. CBD interactions with AEDs are clearly defined. In addition, nutrients, as well as diet, cause changes in pharmacokinetics of some AEDs. The understanding of the pharmacokinetic interactions of the AEDs seems to be important in effective management of epilepsy.

The Effect of Plasma Protein Binding on the Therapeutic Monitoring of Antiseizure Medications

Epilepsy is a widely diffused neurological disorder including a heterogeneous range of syndromes with different aetiology, severity and prognosis. Pharmacological treatments are based on the use, either in mono- or in polytherapy, of antiseizure medications (ASMs), which act at different synaptic levels, generally modifying the excitatory and/or inhibitory response through different action mechanisms. To reduce the risk of adverse effects and drug interactions, ASMs levels should be closely evaluated in biological fluids performing an appropriate Therapeutic Drug Monitoring (TDM). However, many decisions in TDM are based on the determination of the total drug concentration although measurement of the free fraction, which is not bound to plasma proteins, is becoming of ever-increasing importance since it correlates better with pharmacological and toxicological effects. Aim of this work has been to review methodological aspects concerning the evaluation of the free plasmatic fraction of some ASMs, focusing on the effect and the clinical significance that drug-protein binding has in the case of widely used drugs such as valproic acid, phenytoin, perampanel and carbamazepine. Although several validated methodologies are currently available which are effective in separating and quantifying the different forms of a drug, prospective validation studies are undoubtedly needed to better correlate, in real-world clinical contexts, pharmacokinetic monitoring to clinical outcomes.

Past, present and future perspectives of therapeutic drug monitoring in India

Therapeutic drug monitoring (TDM) is the clinical practice of performing drug assays and interpreting results to maintain constant therapeutic concentrations in patients' bloodstream. Conventional TDM was started way back in the 1960s and served to optimise pharmacotherapy by maximising therapeutic efficacy by evaluating efficacy failure and monitoring drug compliance, while minimising adverse events, in drugs with a narrow therapeutic range. Currently, the scope of TDM has been extended to additional indications which are of importance to India. Apart from the conventional indications, TDM can also help combat drug resistance amongst patients treated with antimicrobials, including anti-tubercular drugs and critically ill patients with compromised pharmacokinetics. TDM is also indicated for patients on antiretroviral drugs under specific clinical scenarios and is of high importance to India. Target concentration intervention (TCI) and apriori TDM (by merging TDM with pharmacogenomics) are emerging fields explored in developed nations. The authors sought to assess the evolution of TDM in India and evaluate the potential impact of newer indications in rationalising pharmacotherapy. In the mid-1980s, TDM was presented to India. Despite showing some initial progress, its use is limited to conventional indications. Its utility is also challenged by cost and higher reliance on conventional prescribing practices. However, the newer indications such as antimicrobial resistance, tuberculosis and HIV, with their high prevalence in developing nations, present an opportunity for the growth of TDM in these countries. Indian clinician's awareness and buoyant demands alongside expert contributions from clinical pharmacologists could widen its scope.

Seizure freedom and plasma levels of newer generation antiseizure medications

OBJECTIVES

Contrary to older antiseizure medications (ASM), correlation between plasma levels and seizure freedom is not well defined for newer generation ASM. We assessed correlations between efficacy and newer generation ASM plasma levels in patients with epilepsy.

MATERIALS AND METHODS

Plasma medication levels were measured over two years in consecutive patients taking lamotrigine, levetiracetam, oxcarbazepine, topiramate, zonisamide, lacosamide, perampanel or pregabalin. Seizure freedom was defined as three times the longest inter-seizure pre-treatment interval, or at least one year. Each medication level was stratified according to its position in relation to its proposed reference range (below or in lower half vs upper half or above).

RESULTS

168 patients on stable therapy were included. ASM plasma levels of seizure-free patients were lower than those with ongoing seizures; 45/48 (93.7%) were in the lower half or below the reference ranges, compared to 86/106 (81.1%; p = .004). Lamotrigine plasma levels were significantly lower in seizure-free patients (median 2.4 mg/L range 0.4-6.5 mg/L, none above 6.5 mg/L) compared with those with ongoing seizures (5 mg/L, 0.5-14.2 mg/L; p < .0001). Levetiracetam showed similar results (7.2 mg/L, 1.6-15.1 mg/L; none above 15.1 mg/L in seizure-free patients vs 16.4 mg/L, 0.6-47.7 mg/L; p = .005). Demographics, epilepsy type and polytherapy did not influence the results.

CONCLUSIONS

Efficacy of newer generation ASMs seems to be reached at the lower part or at times even below the reference ranges in drug responsive patients; this could inform regarding titrations of these treatments.

Liquid chromatographic methods for determination of the new antiepileptic drugs stiripentol, retigabine, rufinamide and perampanel: A comprehensive and critical review

The new antiepileptic drugs perampanel, retigabine, rufinamide and stiripentol have been recently approved for different epilepsy types. Being them an innovation in the antiepileptics armamentarium, a lot of investigations regarding their pharmacological properties are yet to be performed. Besides, considering their broad anticonvulsant activities, an extension of their therapeutic indications may be worthy of investigation, especially regarding other seizure types as well as other central nervous system disorders. Although different liquid chromatographic (LC) methods coupled with ultraviolet, fluorescence, mass or tandem-mass spectrometry detection have already been developed for the determination of perampanel, retigabine, rufinamide and stiripentol, new and more cost-effective methods are yet required. Therefore, this review summarizes the main analytical aspects regarding the liquid chromatographic methods developed for the analysis of perampanel, retigabine (and its main active metabolite), rufinamide and stiripentol in biological samples and pharmaceutical dosage forms. Furthermore, the physicochemical and stability properties of the target compounds will also be addressed. Thus, this review gathers, for the first time, important background information on LC methods that have been developed and applied for the determination of perampanel, retigabine, rufinamide and stiripentol, which should be considered as a starting point if new (bio)analytical techniques are aimed to be implemented for these drugs.

Separation of vigabatrin enantiomers using mixed-mode chromatography and its application to determine the vigabatrin enantiomer levels in rat plasma

Mixed-mode chromatography-comprising a mixed phase with reversed and ionic phases, enabling hydrophobic and ion-exchange interactions simultaneously-was applied to identify vigabatrin enantiomers by HPLC with pre-column fluorescence derivatization with 2,5-dioxopyrrolidin-1-yl (4-(((2-nitrophenyl)sulfonyl)oxy)-6-(3-oxomorpholino)quinoline-2-carbonyl)prolinate (Ns-MOK-(S)-Pro-OSu). The MOK-(S)-Pro-vigabatrin enantiomers were efficiently separated within 12 min (total analysis time per sample: 28 min, including washing and equilibrium time for the column). The mobile phase was H₂O/CH₃OH/10 mM ammonium formate (pH 2.0) (20/20/60, v/v/v). Column temperature was maintained at 60℃. The proposed HPLC method could successfully monitor plasma vigabatrin enantiomer levels in rats administered (±)-vigabatrin (50 mg/kg, p.o.).

Redefining the age-specific therapeutic ranges of lamotrigine for patients with epilepsy: A step towards optimizing treatment and increasing cost-effectiveness

OBJECTIVE

The pharmacokinetics of lamotrigine exhibits age-related characteristics. Nevertheless, current evidence regarding the therapeutic range of lamotrigine has been derived almost exclusively from studies in adult patients, and the applicability of this therapeutic range to the pediatric population remains unclear. The purpose of this study was to establish the appropriate age-specific therapeutic ranges of lamotrigine corresponding to adequate clinical responses for patients with epilepsy.

METHODS

This prospective cohort study of therapeutic drug monitoring included 582 Chinese epilepsy patients receiving lamotrigine monotherapy. Patients were divided into three age-related subgroups: (1) toddler and school-age group (2-12 years old, n = 168), (2) adolescent group (12-18 years old, n = 171), and (3) adult group (>18 years old, n = 243). Patients with a reduction in seizure frequency of 50 % or greater than baseline were defined as responders, and the remaining patients were non-responders. The relationship between lamotrigine serum concentrations and clinical response was assessed using multivariate logistic regression analysis. A receiver operating characteristic curve was generated to determine the representative cut-off values of lamotrigine trough levels, to distinguish responders from non-responders. The upper margin of the therapeutic range of lamotrigine was determined by developing concentration-effect curves for the three age-related subgroups.

RESULTS

The median trough levels of lamotrigine were significantly higher in responders than in non-responders from all three age-related groups (P < 0.0001). Results of logistic regression analysis revealed that higher serum concentrations of lamotrigine predicted a higher probability that seizure frequency would be reduced by more than 50 % compared to baseline (adjusted odds ratio: 1.228, 95 % CI: 1.137-1.327; P < 0.0001), and younger children were less likely to be responders (adjusted odds ratio: 1.027, 95 % CI: 1.012-1.043; P = 0.001). Based on a trade-off between sensitivity and specificity, the optimal cut-off values for lamotrigine trough concentrations corresponding to clinical response were 3.29 mg/L, 2.06 mg/L, and 1.61 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. By reducing interpatient variability, the results of the concentration-effect curves suggested no additional clinical benefit from a continued increase of doses for lamotrigine concentrations exceeding 9.08 mg/L, 8.43 mg/L, and 10.38 mg/L in the toddler and school-age group, adolescent group, and adult group, respectively. In conclusion, the therapeutic ranges of lamotrigine trough concentrations corresponding to adequate clinical response were 3.29-9.08 mg/L in the toddler and school-age group, 2.06-8.43 mg/L in the adolescent group, and 1.61-10.38 mg/L in the adult group.

CONCLUSIONS

The study determined age-specific therapeutic ranges corresponding to optimal clinical efficacy for lamotrigine. Our findings lay the foundation for catalyzing novel opportunities to optimize treatment and reduce therapeutic costs. Based on the age-specific therapeutic ranges identified in this study, individualized and cost-effective algorithms for lamotrigine treatment of epilepsy patients may be developed and validated in larger cohort studies of therapeutic drug monitoring.

Case Report: Predicting the Range of Lamotrigine Concentration Using Pharmacokinetic Models Based on Monte Carlo Simulation: A Case Study of Antiepileptic Drug-Related Leukopenia

Lamotrigine (LTG), a wide-spectrum antiepileptic drug, is frequently associated with cutaneous side-effects, whereas hematological side-effects such as leukopenia have rarely been reported for it. We report the case of a 15-year-old Chinese female epileptic patient weighing 60 kg who developed combined asymptomatic leukopenia after receiving concomitant therapy with LTG and valproate acid (VPA). In this case report, antiepileptic drug-related leukopenia may have occurred in definite relation to an increase in LTG concentration and reversed with the discontinuation of VPA. Monte Carlo (MC) simulations were performed to estimate the steady-state serum concentrations (C_ss) of LTG for different dosing regimens in adolescent Chinese epileptic patients weighing the same as the patient considered in the case study, based on pharmacokinetic (PK) models published in past research. Adjustments to the dosage of LTG for the patient were analyzed to illustrate the application of MC simulations and verify the results. The predicted LTG concentrations within a prediction interval between the 10th and 90th percentiles that represented 80% of the simulated populations, could adequately capture the measured LTG concentrations of the patient, indicating that MC simulations are a useful tool for estimating drug concentrations. Clinicians may benefit from the timely probabilistic predictions of the range of drug concentration based on an MC simulation that considers a large sample of virtual patients. The case considered here highlights the importance of therapeutic drug monitoring (TDM) and implementing model-informed precision dosing in the course of a patient’s individualized treatment to minimize adverse reactions.

Personalization of drug dose thematic issue: introduction article

INTRODUCTION

The need to individualize a drug dosage and adjust it to a patient's physiological and/or pathophysiological status is rarely satisfied in routine clinical practice, primarily because of complexity of the adjustment task.

AREAS COVERED

The aim of this article is to shed light to basic principles of drug dosage individualization in the most frequent clinical states that affect pharmacokinetics of drugs. The principles are derived from published clinical studies conducted on diverse patient populations, using non-compartmental pharmacokinetic model.

EXPERT OPINION

Simple, but sufficiently exact, way to calculate appropriate drug dose for a patient is the one based on target average steady-state concentration and non-compartmental pharmacokinetic model. If target steady-state drug concentration and dosage interval are considered fixed, maintenance dose could be adjusted on the basis of expected changes of total drug clearance and bioavailability, while loading dose should be related to changes of volume of distribution and bioavailability. Relative increase or decrease of these pharmacokinetic parameters in regard to normal values in healthy persons is translated to relative (percentual) increase or decrease of maintenance and loading doses recommended in the drug monograph.

Therapeutic Drug Monitoring of Antiseizure Medications Using Volumetric Absorptive Microsampling: Where Are We?

Therapeutic drug monitoring (TDM) of antiseizure medications (ASMs) represents a valuable tool to establish an appropriate patient therapy, to collect important information about drugs’ interactions and to evaluate patient’s metabolic capabilities. In recent years, a new volumetric absorptive microsampling technique using VAMS^® technology and Mitra^® devices, consisting of a sampling technique for the collection of fixed-volume capillary blood, was developed. These new devices provide a new home-sampling technique for whole blood that has been spread out to simplify sample collection from finger-pricks. This review is aimed to compare published articles concerning the application of VAMS^® in epilepsy and to identify the strengths and improvement points for the TDM of antiseizure medications. VAMS^® allowed a minimally invasive blood sampling even in the absence of trained personnel. Good stability data have indicated that storage and delivery can be facilitated only for specific ASMs. Trueness and precision parameters have been evaluated, and the hematocrit (HCT) effect was minimized.

Predictive Performance of Population Pharmacokinetic Models of Levetiracetam in Children and Evaluation of Dosing Regimen

Levetiracetam is a broad-spectrum antiepileptic drug that exhibits high interindividual variability in serum concentrations in children. A population pharmacokinetic approach can be used to explain this variability and optimize dosing schemes. The objectives are to identify the best predictive population pharmacokinetic model for children and to evaluate recommended doses using simulations and Bayesian forecasting. A validation cohort included children treated with levetiracetam who had a serum drug concentration assayed during therapeutic drug monitoring. We assessed the predictive performance of all the population pharmacokinetic models published in the literature using mean prediction errors, root mean squared errors, and visual predictive checks. A population model was finally constructed on the data, and dose simulations were performed to evaluate doses. We included 267 levetiracetam concentrations ranging from 2 to 69 mg/L from 194 children in the validation cohort. Six published models were externally evaluated. Most of the models underestimated the variability of our population. A 1-compartment model with first-order absorption and elimination with allometric scaling was finally fitted on our data. In our cohort, 57% of patients had a trough concentration <12 mg/L and 12% <5 mg/L. To reach a trough concentration >5 mg/L, doses ≥30 mg/kg/d for patients ≤50 kg and ≥2000 mg/d for patients >50 kg are required. In our population, a high percentage of children had low trough concentrations. Our population pharmacokinetic model could be used for therapeutic drug monitoring of levetiracetam in children.