Antiepileptic drugs--best practice guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies

Association of the ward pharmacy service with active implementation of therapeutic drug monitoring for vancomycin and teicoplanin-an epidemiological surveillance study using Japanese large health insurance claims database

Background

Ward pharmacists are required for the active implementation of therapeutic drug monitoring (TDM). This epidemiological study verified whether Japanese ward pharmacists contribute to improving the TDM implementation proportions of anti-methicillin-resistant Staphylococcus aureus (MRSA) agents using the large health insurance claims database.

Methods

The patients who received intravenous anti-MRSA agents from April 2012 to March 2017 were enrolled. We defined ward pharmacy service as the “drug management and guidance fee” and/or “inpatient pharmaceutical services premium”. In addition, implementation of TDM was identified by “the specific drug treatment management fee”. We compared the proportions of TDM implementation for vancomycin (VCM), teicoplanin (TEIC), and arbekacin (ABK) in the ward and non-ward pharmacy service groups. To avoid confounding, the propensity score method was employed. Moreover, the clinical variables affecting TDM implementation in each anti-MRSA agent were analyzed by using a multiple logistic regression model.

Results

The following number of patients were included in the study: VCM (n = 2138), TEIC (n = 596), and ABK (n = 142). After propensity score matching, the proportions of TDM implementation for VCM and TEIC were higher in the ward pharmacy service group than in the non-ward pharmacy service group (VCM: 69.2% vs 60.3%, TEIC: 51.4% vs 34.7%), while no significant difference was observed for ABK (21.2% vs 23.1%). As independent clinical variables affecting TDM implementation for VCM and TEIC, several clinical variables, including ward pharmacy services, were extracted. In contrast, no clinical variables were extracted for ABK.

Conclusions

We found that the ward pharmacy service is associated with the active implementation of TDM for anti-MRSA agents, such as VCM and TEIC.

Drug-drug and drug-food interactions in an infant with early-onset SCN2A epilepsy treated with carbamazepine, phenytoin and a ketogenic diet

Sodium channel 2 subunit α (SCN2A) mutations cause difficult-to-treat early-onset epilepsy. Effective treatment includes high-dose phenytoin or carbamazepine ± ketogenic diet (KD). We describe an infant with early-onset SCN2A-epilepsy with subtherapeutic carbamazepine concentration during transition from phenytoin treatment to avoid long-term neurotoxicity. The transition from high-dose phenytoin (20 mg kg^-1 d^-1 , concentration: ≥20 mg/L) with KD, to carbamazepine (50-75 mg kg^-1 d^-1 , concentration: 9-12 mg/L) lasted 85 days, which we suspected was due to significant drug-drug and/or drug-food interactions. Model-based analysis of carbamazepine pharmacokinetics quantified significant time- and dose-dependent phenytoin-mediated CYP3A4 induction and carbamazepine concentration-dependent auto-induction (apparent clearance increased up to 2.5/3-fold). Lower carbamazepine concentrations under KD were modelled as decreased relative bioavailability (44%), potentially related to decreased fraction absorbed (unexpected for this lipophilic drug), increased intestinal/hepatic metabolism and/or decreased protein-binding with KD. This suggests importance of carbamazepine-concentration monitoring during KD-introduction/removal and necessity of high carbamazepine doses to achieve therapeutic concentrations, especially in infants treated with high-dose phenytoin.

Critical Care Management of Status Epilepticus at a Tertiary Care University Hospital

BACKGROUND

Status epilepticus (SE) is a neurological emergency associated with significant morbidity and mortality. The objective of this study was to review the critical care management of patients with SE focusing on antiepileptic drugs (AEDs) as well as to determine the optimal dosing strategies of phenytoin (PHT) and predictors of its effectiveness.

METHODS

A retrospective chart review of adult patients with SE admitted to the University of Alberta Hospital, Canada, was conducted.

RESULTS

Fifty-six admissions were included. Benzodiazepines (BDZs) were initially given in 89% of our patients. Following BDZs, PHT and levetiracetam were the most commonly initiated AEDs as first- and second-line agents and were deemed effective in 30/44 and 5/11 patients, respectively. Patients who received a PHT loading dose (LD) of 1000 mg were less likely to reach target levels compared with a weight-based LD ≥15 mg/kg (29% vs. 60%). Likewise, patients who received a maintenance dose (MD) of 300 mg/day were less likely to reach target compared with 400 mg/day or >5 mg/kg per day; however, this did not reach statistical significance. Three variables were found to be associated with PHT effectiveness: tonic-clonic SE (OR 5.01, 95% CI 1.02-24.7, p = 0.048), history of seizures and BMI <30 kg/m2 (OR 0.16, 95% CI 0.03-1.07, p = 0.059).

CONCLUSIONS

Further studies of the predictors of PHT effectiveness, specifically obesity, are necessary to help individualize care. Finally, we suggest that PHT should be loaded according to the guidelines as 20 mg/kg followed by an MD of at least 400 mg/day or >5 mg/kg per day.

[Significant Changes Associated with the Transition from Outsourcing to In-hospital Therapeutic Drug Monitoring of Novel Antiepileptics]

For many of the novel antiepileptics, immunoassays, used for routine therapeutic drug monitoring (TDM), cannot be used. We could monitor eight novel antiepileptics using an LC/MS method since July 2017. The purpose of this study was to evaluate the significant changes associated with the transition from outsourcing to in-hospital monitoring of novel antiepileptics. The number of measurements of novel antiepileptics was significantly increased during the first (p<0.01) and second (p<0.001) years of in-hospital monitoring as compared to that one year prior to in-hospital monitoring which was outsourced. The proportion of measurements of novel antiepileptics to all antiepileptics was 19.7%, 31.1%, and 38.4% during outsourcing, and first, and second years of in-hospital monitoring, respectively. The measurement cost was significantly reduced during the first (p<0.001) and second (p<0.001) years of in-hospital monitoring as compared to that during outsourcing. In addition, the revenue from TDM of antiepileptic drugs was significantly increased during the first (p<0.05) and second (p<0.01) years of in-hospital monitoring as compared with that during outsourcing. In conclusion, the switch from outsourcing to in-hospital monitoring led to an increase in the number of orders, a reduction in the measurement-related expenses of novel antiepileptics, and an increase in the revenue from TDM of antiepileptic drugs, which could promote the proper use of novel antiepileptics through TDM.

Population Pharmacokinetics of IV Phenobarbital in Neonates After Congenital Heart Surgery

OBJECTIVES

To develop a population pharmacokinetic model for IV phenobarbital in neonates following cardiac surgery and perform simulations to identify optimal dosing regimens.

DESIGN

Retrospective single-center pharmacokinetic study.

SETTING

Cardiac ICU at Children's Hospital of Philadelphia.

PATIENTS

Consecutive neonates who received greater than or equal to one dose of IV phenobarbital and had greater than or equal to one phenobarbital concentration drawn per standard of care from June 15, 2012, to October 15, 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A population pharmacokinetic model was developed using nonlinear mixed-effects modeling. Simulations were performed using the final model variables. Optimal phenobarbital loading doses were determined based on attainment of peak and maintenance concentrations between 20 and 40 mg/L. A total of 37 neonates contributed 159 pharmacokinetic samples. The median (range) weight, postmenstrual age, and postnatal age were 3.2 kg (1.3-3.8), 39 2/7 weeks (28 2/7 to 42 6/7), and 5 days (0-26 d), respectively. Twelve patients (32%) were on extracorporeal membrane oxygenation. An one-compartment model best described the data. The final population pharmacokinetic model included (1) weight and postnatal age for clearance and (2) weight, extracorporeal membrane oxygenation, and albumin for volume of distribution. In neonates not on extracorporeal membrane oxygenation, loading doses of 30 and 20 mg/kg reached goal concentration with albumin values less than or equal to 3 and 3.5 mg/dL, respectively. Loading doses of 30 mg/kg reached goal concentration on extracorporeal membrane oxygenation regardless of albumin values. Maintenance doses of 4-5 mg/kg/d reached goal concentration in all neonates.

CONCLUSIONS

In neonates following cardiac surgery, phenobarbital clearance increased with postnatal age. Volume of distribution increased with extracorporeal membrane oxygenation and lower albumin values. Loading doses of 30 mg/kg on extracorporeal membrane oxygenation and 20-30 mg/kg without extracorporeal membrane oxygenation were needed to reach goal concentration based on simulations.

A perspective on the physicochemical and biopharmaceutic properties of marketed antiseizure drugs-From phenobarbital to cenobamate and beyond

The success rate from first time in man to regulatory approval of central nervous system (CNS) drugs is lower than the overall success rate across all therapeutic indications (eg, cardiovascular, infectious diseases). To understand the reasons for drug-candidate failure and to capture trends in antiseizure drug (ASD) design, we have analyzed the physicochemical and biopharmaceutical properties of marketed ASDs in comparison with new ASDs in development. Our comparative analysis included molecular weight (MW), logP, polar surface area (PSA), the "Lipinski rule of five," and the CNS Multiparameter Optimization (MPO) score. LogP is the logarithm of a drug-partition coefficient (P) between n-octanol and water. PSA is the molecule's surface sum of its polar atoms. ASDs' biopharmaceutical properties were classified according to their water solubility, permeability, and route of elimination as outlined by the Biopharmaceutics Classification System (BCS) and Biopharmaceutics Drug Disposition Classification System (BDDCS). For old ASDs (1912-1990), logP, PSA, and CNS MPO values ranged between 0.4 and 2.8, 37 and 87 Å² , and 4.4 and 6.0, respectively. For second-generation ASDs (1990-2008), PSA values ranged between 39 and 116 Å² . However, logP values showed a difference between the lipophilic (logP = 0.3-3.21) and hydrophilic (logP = -0.6 to -2.16) ASDs. For third-generation ASDs (2008-2020), logP and PSA ranged between 0.3 and 3.5 and between 57 and 76 Å² , respectively. The mean CNS MPO scores of all marketed ASDs were similar, ranging between 4.9 and 5.4, and were similar to those of the ASDs in development (3.5-5.8). Most ASDs belong to BCS and BDDCS classes 1 and 2. MW, logP, CNS MPO score, and PSA assess lipophilicity and correlate with antiseizure activity. To succeed, a new small-molecule ASD must have MW < 375 and PSA < 140Ų , belong to BCS and/or BDDCS class 1 or 2, and obey the Lipinski rule of five: logP < 5, MW < 500, and <5 and <10 of hydrogen-bond donors and acceptors, respectively. The similarity in the MW, logP, and PSA values of marketed and new drugs in development indicates a conservative trend in ASD design.

Relationship between saliva and plasma rufinamide concentrations in patients with epilepsy

The assay of saliva samples provides a valuable alternative to the use of blood samples for therapeutic drug monitoring (TDM), at least for certain categories of patients. To determine the feasibility of using saliva sampling for the TDM of rufinamide, we compared rufinamide concentrations in paired samples of saliva and plasma collected from 26 patients with epilepsy at steady state. Within-patient relationships between plasma rufinamide concentrations and dose, and the influence of comedication were also investigated. Assay results in the two tested fluids showed a good correlation (r²  = .78, P < .0001), but concentrations in saliva were moderately lower than those in plasma (mean saliva to plasma ratio = 0.7 ± 0.2). In eight patients evaluated at three different dose levels, plasma rufinamide concentrations increased linearly with increasing dose. Patients receiving valproic acid comedication had higher dose-normalized plasma rufinamide levels than patients comedicated with drugs devoid of strong enzyme-inducing or enzyme-inhibiting activity. Overall, these findings indicate that use of saliva represents a feasible option for the application of TDM in patients treated with rufinamide. Because rufinamide concentrations are lower in saliva than in plasma, a correction factor is needed if measurements made in saliva are used as a surrogate for plasma concentrations.

Epilepsy Research in Mali: A Pilot Pharmacokinetics Study on First-Line Antiepileptic Drug Treatment

BACKGROUND AND PURPOSE

The indication and benefit of plasma level of antiepileptic (AEDs) has been debating in the monitoring of people living with epilepsy and the epilepsy treatment gap has largely been documented in developed countries. This study was aimed to highlight the epilepsy treatment gap between rural and urban Mali.

METHODS

We conducted a pilot study on AEDs treatment from September 2016 to May 2019. For 6 months, 120 children and young adults living with epilepsy (rural site, 90; urban site, 30) received phenobarbital, valproic acid and/or carbamazepine. At our rural study site, we determined the AED plasma levels, monitored the frequency, severity and the duration of seizure, and administered monthly the McGill quality of life questionnaire. At our urban study site, each patient underwent an electroencephalogram and brain computed tomography scan without close monitoring.

RESULTS

At the rural study site, patients were mostly on monotherapy; AED levels at 1 month (M1) (n=90) and at 3 months (M3) (n=27) after inclusion were normal in 50% at M1 versus 55.6% at M3, low in 42.2% at M1 versus 33.3% at M3 and high in 7.8% at M1 versus 11.1% at M3. AED levels at M1 and at M3 were significantly different p<0.0001. By M3, seizures (n=90) were <1/month in 26.7%, and lasted less than 1 minute in 16.7%. After a yearlong follow up, all 90 patients reported a good or excellent quality of life. At our urban study site, patients (n=30) were on carbamazepine and valproid acid in 66.67% and monotherapy (carbamazepine) in 33.33%. By November 2018, only six out 30 patients (on bi-therapy) were still taking their medications.

CONCLUSIONS

Epilepsy diagnostic and treatment are a real concern in Mali. Our data showed appropriate AED treatment with close follow up resulted in a better quality of life of patients in rural Mali. We will promote the approach of personalized medicine in AED treatment in Mali.

Valproic Acid Impacts the Growth of Growth Plate Chondrocytes

A range of bone abnormalities including short stature have been reported to be associated with the use of antiepileptic drugs (AEDs) in children. Exactly how AEDs impact skeletal growth, however, is not clear. In the present study, rat growth plate chondrocytes were cultured to study the effects of AEDs, including valproic acid (VPA), oxcarbazepine (OXA), levetiracetam (LEV), lamotrigine (LTG), and topiramate (TPM) on the skeletal growth. VPA markedly reduced the number of chondrocytes by apoptosiswhile other AEDs had no effect. The apoptosis associated noncleaved and cleaved caspase 3, and caspases were increased by exposure to VPA, which up-regulated cyclooxygenase 2 (COX-2) mRNA and protein levels likely through histone acetylation. The COX-2 inhibitor NS-398 attenuated the effects of VPA up-regulating COX-2 expression and decreased VPA-induced caspase 3 expression. The use of VPA in children should be closely monitored or replaced, where appropriate, by AEDs which do not apparently affect the growth plate chondrocytes.

Clinical characteristics and fetal outcomes in women with epilepsy with planned and unplanned pregnancy: A retrospective study

PURPOSE

To compare the antiepileptic drug (AED) treatment patterns, seizure control, and folic acid supplementation between planned and unplanned pregnancy in women with epilepsy (WWE) and to investigate the effects of planned pregnancy on fetal outcomes.

METHODS

A prospectively collected database including WWE with pregnancy from Feb 2010 to Dec 2018 was retrospectively analyzed. Planned pregnancy was defined as WWE being regularly supervised by epileptologists from the time of intended pregnancy until delivery. Clinical characteristics and fetal outcomes were compared between the planned and unplanned pregnancy groups. Logistic regression was used to identify modifiable factors associated with adverse fetal outcomes.

RESULTS

A total of 188 planned pregnancies and 289 unplanned pregnancies were enrolled in our study. Among planned pregnancies, 66.0 % took AED monotherapy, and 32.4 % received polytherapy. Among unplanned pregnancies, 58.1 % didn't take AEDs, 28.0 % took monotherapy, and 12.8 % received polytherapy. The planned pregnancies had less generalized tonic-clonic seizures (P = 0.002) and higher proportion of being seizure-free (41.0 % vs. 22.8 %; P <0.001). All planned pregnancies took folic acid while 39.8 % of unplanned pregnancies never took it (P <0.001). The planned pregnancies had less rates of induced abortions (2.7 % vs. 13.5 %; P <0.001), preterm births (3.3 % vs. 20.4 %; P <0.001), and major congenital malformations (1.6 % vs. 7.5 %; P = 0.016). Pregnancy planning was independently associated with adverse fetal outcomes (adjusted OR, 0.14; 95 % CI, 0.08-0.27; P <0.001).

CONCLUSION

Planned pregnancy in WWE contributes to more optimized AED pattern, better seizure control, more appropriate folic acid supplementation, and less adverse fetal outcomes.

Usefulness of saliva for perampanel therapeutic drug monitoring

OBJECTIVE

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.

METHODS

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.

RESULTS

Thirty patients were enrolled, aged 16 to 60; 10 (33%) were women. Patients received 2 to 12 mg (mean, 6 mg) 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).

SIGNIFICANCE

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.

Characterization and treatment of spontaneous recurrent seizures following nerve agent-induced status epilepticus in mice

PURPOSE

To develop and characterize a mouse model of spontaneous recurrent seizures following nerve agent-induced status epilepticus (SE) and test the efficacy of existing antiepileptic drugs.

METHODS

SE was induced in telemeterized male C57Bl6/J mice by soman exposure, and electroencephalographic activity was recorded for 4-6 weeks. Mice were treated with antiepileptic drugs (levetiracetam, valproic acid, phenobarbital) or corresponding vehicles for 14 d after exposure, followed by 14 d of drug washout. Survival, body weight, seizure characteristics, and histopathology were used to characterize the acute and chronic effects of nerve agent exposure and to evaluate the efficacy of treatments in mitigating or preventing neurological effects.

RESULTS

Spontaneous recurrent seizures manifested in all survivors, but the number and frequency of seizures varied considerably among mice. In untreated mice, seizures became longer over time. Moderate to severe histopathology was observed in the amygdala, piriform cortex, and CA1. Levetiracetam provided modest improvements in neurological parameters such as reduced spike rate and improved histopathology scores, whereas valproic acid and phenobarbital were largely ineffective.

CONCLUSIONS

This model of post-SE spontaneous recurrent seizures differs from other experimental models in the brief latency to seizure development, the occurrence of seizures in 100 % of exposed animals, and the lack of damage to CA4/dentate gyrus. It may serve as a useful tool for rapidly and efficiently screening novel therapies that would be effective against severe epilepsy cases.

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.

Serum Levels of Valproic Acid and Carbamazepine Do Not Correlate Well with End-Organ Dysfunction

BACKGROUND

Serum levels of anticonvulsants are commonly ordered; however, the clinical utility of these laboratory tests is unclear. Clarifying the significance of anticonvulsant drug levels is essential to allow physicians to make appropriate management decisions. We aimed to determine to what extent elevated serum levels of valproic acid (VPA) and carbamazepine (CBZ) correlate with laboratory indications of end-organ dysfunction.

METHODS

We reviewed a consecutive sample of patients 0-18 years of age who, over a 2-year period, had at least one blood collection in which (1) serum [VPA] or [CBZ] was tested; and (2) at least one of the following tests was performed: alanine aminotransferase (ALT), aspartate aminotransferase (AST), platelets, white blood cells (WBC), ammonia, sodium.

RESULTS

913 and 300 blood collections met criteria for VPA and CBZ, respectively. A slight increased frequency of having any abnormal laboratory value for elevated [VPA] compared to low/normal [VPA] was observed (p = 0.02; relative risk 1.27), while there was no difference in frequency of having any abnormal lab value for CBZ, nor were there significant differences for the individual lab values. When ALT and AST were plotted against [VPA] and [CBZ], no significant correlation was observed.

CONCLUSION

Serum [VPA] and [CBZ] are poor indicators of risk for drug-induced end-organ dysfunction. There are likely other, individualized risk factors that explain why certain patients develop adverse effects from these medications.

Randomized controlled trial of pregabalin for analgesia after surgical treatment of intervertebral disc disease in dogs

OBJECTIVE

To assess the effect of perioperative pregabalin on pain behavior in dogs after intervertebral disc surgery.

STUDY DESIGN

Prospective, randomized, controlled clinical trial with a blinded observer.

ANIMALS

Forty-six client-owned dogs undergoing intervertebral disc surgery.

METHODS

Dogs were randomly assigned to two groups, with the placebo group receiving opioids alone and the pregabalin group receiving opioids plus pregabalin. Opioid analgesia consisted of 0.6 mg/kg l-methadone given intravenously at anesthetic induction, followed by 0.2 mg/kg given at 8, 16, and 24 hours after extubation and fentanyl patches applied at the end of surgery. Pregabalin was given orally (4 mg/kg) 1 hour before anesthesia, followed by postoperative treatment three times per day (4 mg/kg) for 5 days. The outcome measures were the treatment-group differences in peri-incisional mechanical sensitivity and Glasgow Composite Measure Pain Scale (CMPS-SF) assessed during the first 5 postoperative days. Pregabalin serum concentrations were measured after 24, 72, and 120 hours.

RESULTS

Pregabalin reduced pain levels in the treatment group by a mean of 2.5 CMPS-SF units (95% confidence interval [CI] = -3.19 to -1.83, P < .001) compared with the control group during the study period. Pregabalin increased the mechanical nociceptive threshold by a mean of 6.89 N per day (95% CI = 1.87-11.92, P < .001) and of 7.52 N per day (95% CI = 2.29-12.77, P < .001) during the study period, depending on location. Mean levels of serum pregabalin were 5.1, 4.71, and 3.68 μg/mL at 24, 72, and 120 hours postoperatively, respectively.

CONCLUSION

Postoperative signs of pain after surgical treatment of intervertebral disc herniation (IVDH) were reduced when dogs received perioperative pregabalin rather than opioids alone.

CLINICAL SIGNIFICANCE

Perioperative pregabalin reduces postoperative pain after surgical treatment of IVDH.

Influence of dose and antiepileptic comedication on brivaracetam serum concentrations in patients with epilepsy

The aim of this study was to investigate the influence of concomitant antiepileptic drugs (AEDs) on brivaracetam (BRV) trough serum concentrations. A total number of 368 routinely collected blood samples from 148 inpatients from Mara Hospital (Bethel Epilepsy Center) and von Bodelschwingh Foundation Bethel were retrospectively evaluated. Generalized estimation equations (GEEs) were used for statistical analysis. GEE analyses showed that BRV trough serum concentrations were significantly lower in patients with strong enzyme-inducing AEDs (carbamazepine, phenytoin, and/or phenobarbital/primidone, -49%), but were not affected by concomitant intake of oxcarbazepine or eslicarbazepine. Age and gender did not have a significant effect. An alternative GEE model analyzing the BRV level-to-dose ratios yielded comparable results. Our results from routine therapeutic drug monitoring data indicate that the effect of enzyme-inducing AEDs on BRV serum concentrations is stronger than the 20%-30% reduction in BRV exposure previously reported in pharmacokinetics studies. Further research is necessary to evaluate these differences and to elucidate possible clinical consequences.

Pharmacokinetic and pharmacodynamic modeling of levetiracetam: investigation of factors affecting the clinical outcome

This study aimed to evaluate the pharmacokinetics and pharmacodynamics of oral levetiracetam therapy in drug refractory adult epileptic outpatients, as well as factors affecting them. Concentration-time data were collected at steady state, while seizure recurrence was monitored for 13 months. Non-linear mixed effects modeling was applied, and covariates assessed included weight, height, age, daily dose and creatinine clearance.Plasma concentrations of levetiracetam were best described by a one-compartment pharmacokinetic model (V/F = 34.7 L) with first-order absorption (ka = 0.616 h^-1) and clearance (CL/F = 3.26 L/h). Patient's CrCL was found to significantly affect levetiracetam clearance (beta = 0.795). Time to seizure occurrence followed an exponential distribution and the mean time to seizure occurrence was estimated Te = 22.08 days. Seizure rate per month followed a Poisson distribution, while mean seizure rate per month was estimated λ = 1.33. Daily dose significantly affected the mean estimated time to seizure (beta = -2.2) and the mean monthly seizure rate (beta = 2.27) in a reverse way. Using discrete time Markov chains, it was shown that the transition probability from focal seizures to focal to bilateral tonic-clonic is significantly altered in relation to patient's CrCL.Simulations showed that dose should be adjusted in relation to CrCL, while low doses of levetiracetam are more effective for seizure control. Modeling and simulation in every-day clinical practice may provide significant information for the optimization of seizure control using well-known agents.

[Pitch perception modification due to antiepileptics: A literature and pharmacovigilance databases review]

Pitch perception modifications are among the little-known adverse effects observed with antiepileptics, mainly affecting patients treated with carbamazepine (CBZ). Here, we describe an original French case of pitch perception modification due to CBZ resulting in perfect pitch loss. We also reviewed the literature as well as French and world health organisation global pharmacovigilance database. The case report concerns a 22-year-old patient with perfect pitch with untreated left temporal partial epilepsy. Following a generalized seizure, the introduction of CBZ prolonged release (200mg twice a day) is decided. As soon as CBZ is introduced, the patient notices a change in pitch perception, about a semitone lower. This adverse effect persisted despite a gradual decrease in doses. The patient reported a total recovery of his perfect pitch when CBZ stopped completely 11 years later. In the French pharmacovigilance database, only one other case of pitch perception modification under CBZ was recorded (no cases were found with oxcarbazepine, lacosamide, sodium valproate, lamotrigine, levetiracetam, phenobarbital, phenytoin, primidone, ethosuximide, vigabatrine, felbamate, gabapentin, tiagabine and topiramate). In the literature, 27 cases of pitch perception modification have been published with CBZ, 1 case with oxcarbazepine and 1 case with lacosamide. Pitch perception modification is a very rare adverse effect of CBZ, oxcarbazepine and lacosamide, identified in the literature mainly in the Japanese population, in experienced musicians. A rapid onset after the introduction of treatment, a complete resolution of symptoms, in most cases upon discontinuation of treatment, is observed, with no sequelae reported. Due to the impact on quality of life, especially in patients whose profession is related to music, knowledge of this adverse event seems important to evoke this diagnosis.

Factors Associated with Good Seizure Control in Patients on Valproic Acid

Objective

This study aims to generate a reference range for valproic acid (VPA) in this cohort and determine the factors associated with good seizure control in patients taking this drug.

Materials and Methods

We conducted a prospective, cohort, observational study among patients with epilepsy who received VPA treatment at Hospital Kuala Lumpur. The patients were considered to have good control if they had a 50% or higher seizure reduction in the one-year study period compared with the previous year. The VPA reference range was generated from those patients who had good control and whose drug concentration values were available. Multiple logistic regression analysis with a backward likelihood ratio method was applied to assess the predicting factors for good seizure control.

Results

A total of 242 patients were recruited and followed up for one year. The VPA reference range was determined to be 40-85 mg/L. After multivariate analysis, significant predictive variables for good control were monotherapy [adjusted OR 4.74, 95% CI: 2.258, 9.947, p<0.001], non-smoking [adjusted OR 3.23, 95% CI: 1.099, 9.473, p=0.033], normal brain imaging results [adjusted OR 5.83, 95% CI: 2.507, 13.552, p<0.001], and the absence of stress [adjusted OR 19.98, 95% CI: 9.255, 42.764, p<0.001].

Conclusion

Monotherapy, non-smoking, normal brain imaging results, and the absence of stress are predictive of good seizure control in patients on VPA. However, a serum concentration of VPA in the reference range failed to predict good seizure control.

The Steps to Therapeutic Drug Monitoring: A Structured Approach Illustrated With Imatinib

Pharmacometric methods have hugely benefited from progress in analytical and computer sciences during the past decades, and play nowadays a central role in the clinical development of new medicinal drugs. It is time that these methods translate into patient care through therapeutic drug monitoring (TDM), due to become a mainstay of precision medicine no less than genomic approaches to control variability in drug response and improve the efficacy and safety of treatments. In this review, we make the case for structuring TDM development along five generic questions: 1) Is the concerned drug a candidate to TDM? 2) What is the normal range for the drug's concentration? 3) What is the therapeutic target for the drug's concentration? 4) How to adjust the dosage of the drug to drive concentrations close to target? 5) Does evidence support the usefulness of TDM for this drug? We exemplify this approach through an overview of our development of the TDM of imatinib, the very first targeted anticancer agent. We express our position that a similar story shall apply to other drugs in this class, as well as to a wide range of treatments critical for the control of various life-threatening conditions. Despite hurdles that still jeopardize progress in TDM, there is no doubt that upcoming technological advances will shape and foster many innovative therapeutic monitoring methods.

Clinical Impact of Co-medication of Levetiracetam and Clobazam with Proton Pump Inhibitors: A Drug Interaction Study

BACKGROUND

Clobazam (CLBZ) metabolized primarily by Cytochrome P-450 isoenzyme CYP3A4 than with CYP2C19, Whereas Levetiracetam (LEV) is metabolized by hydrolysis of the acetamide group. Few CYP enzymes are inhibited by Proton Pump Inhibitors (PPIs) Pantoprazole, Esomeprazole, and Rabeprazole in different extents that could affect drug concentrations in blood. The aim of the present study was to evaluate the effect of these PPIs on the plasma concentrations of LEV and CLBZ.

METHODS

Blood samples from 542 patients were included out of which 343 were male and 199 were female patients and were categorized as control and test. Plasma samples analyzed using an HPLC-UV method. Plasma concentrations were measured and compared to those treated and those not treated with PPIs. One way ANOVA and games Howell post hoc test used by SPSS 20 software.

RESULTS

CLBZ concentrations were significantly 10 folds higher in patients treated with Pantoprazole (P=0.000) and 07 folds higher in patients treated with Esmoprazole and Rabeprazole (P=0.00). Whereas plasma concentration of LEV control group has no statistical and significant difference when compared to pantoprazole (P=0.546) and with rabeprazole and esomeprazole was P=0.999.

CONCLUSION

The effect of comedication with PPIs on the plasma concentration of clobazam is more pronounced for pantoprazole to a greater extent when compared to esomeprazole and rabeprazole. When pantoprazole is used in combination with clobazam, dose reduction of clobazam should be considered, or significance of PPIs is seen to avoid adverse effects.

Racial variations in lacosamide serum concentrations in adult patients with epilepsy

Lacosamide (LCM) is a third-generation anti-epileptic drug (AED) for partial-onset epilepsy with minimal hepatic metabolism and drug-drug interactions. The impact of individual patient variables such as race on drug metabolism have been under-reported in AEDs and LCM has not been specifically investigated. Our aim was to assess the role race plays on serum LCM levels in the management of epilepsy. Thus, we retrospectively reviewed patients with focal seizures who received LCM and had LCM levels as part of their routine clinical care in our Level IV Epilepsy Center. Variables including age, race, gender, LCM serum levels, LCM daily dose, and concomitant AEDs were collected and analyzed. A total of 93 patients with 1-3 clinic visits yielded 122 LCM serum levels. African Americans (AA) comprised 62.3% of our serum samples. Daily LCM doses averaged 350 mg/day (range 50-1000 mg/day). Eighty-nine percent of patients took 1-2 other AEDs. Overall, AA patients had lower LCM levels (mean 6.8 μg/mL) compared to White patients (mean of 7.1 μg/mL) (p = .017) even when considering for the daily dose effect (p = .007). Analysis of co-variables did not have significant effect on LCM levels. Overall, AA patients had a weaker relationship between LCM daily dose (adjusted for weight) and serum levels as compared to White patients and require a higher LCM dose per weight to achieve similar levels. Differences in pharmacogenetics may play an important role in these findings and focus on how these variations impact seizure burden.

Managing the patient with epilepsy and renal impairment

PURPOSE

Epilepsy affects more than 50 million people worldwide and its management can be complicated by comorbidities such as impaired renal function. To optimize epilepsy control in patients with kidney disease, clinicians need to be aware of how antiepileptic drugs (AEDs) are affected by impaired renal function and how the kidneys are affected by epilepsy management strategies. Herein we present a narrative review with systematic literature search to discuss the use of AEDs in patients with renal impairment, including those undergoing dialysis, as well as the nephrotoxic effects of some AEDs. We finally conclude the article by providing practical tips about our approach to using AEDs in the setting of renal disease.

METHODS

A literature search targeting epilepsy management in patients with kidney disease was performed in MEDLINE database (1946 to 7th Jan 2019).

RESULTS

A total of 1193 articles were found. After duplicate removal, title and abstract screening followed by full text screening, a total of 110 references were included in this review. Additional information was included from drug product monographs.

CONCLUSION

The disposition of AEDs can be altered in patients with impaired renal function, leading to a higher risk of AED toxicity or therapy failure. Renal dosage adjustment and close monitoring is recommended. Although AED-induced nephrotoxicity is rare, it is unpredictable and clinicians need to vigilant about this possibility. In addition, AEDs renal adverse reactions and renal drug interactions should be considered when selecting an AED.

Topiramate pharmacokinetics in neonates undergoing therapeutic hypothermia and proposal of an optimised dosing schedule

AIM

The adequate dosing of topiramate in neonates undergoing therapeutic hypothermia has not been established. The aim of this study was to design a dosing schedule capable of providing topiramate serum concentrations within the accepted therapeutic range.

METHODS

Neonates (n = 52) with hypoxic ischaemic encephalopathy and subjected to therapeutic hypothermia were dosed with topiramate, 5 mg/kg on day one and 3 mg/kg on days two to five, to decrease seizure events. A total of 451 topiramate serum concentrations obtained in the patients were used to develop a population pharmacokinetic model using a non-linear mixed-effects modelling approach.

RESULTS

A one-compartment model with first-order absorption and two different clearance terms, one for the cooling period and another for the post-warming period, were used to describe the concentration-time topiramate data. The probability of no-seizure events could not be related to topiramate concentrations, which was attributed to excessively low topiramate concentrations. A modified dosage schedule was designed with the aim of obtaining more than 90% of patients with topiramate concentrations within the therapeutic range after the first dose.

CONCLUSION

The dosage schedule of topiramate in these patients should be modified with the aim of decreasing the frequency of seizure events.

Diagnostic evaluation and management of seizures and status epilepticus in children with known epilepsy or new-onset seizures: A retrospective and comparative analysis

OBJECTIVES

The purpose of this study was to describe and compare the initial management, including clinical/biological investigation and treatment, of new-onset seizures and status epilepticus (SE) in children versus seizures and SE in those with known epilepsy.

METHODS

This was a retrospective, single-center, observational study conducted in an urban pediatric hospital in Paris. All patients, aged from 1 month to 18 years, admitted to the pediatric intensive care unit, the high-dependency care unit, and those who required hospitalization in the short-term unit of the emergency department between January 1 and December 31, 2014 for seizures and/or SE were included.

RESULTS

We analyzed the data of 190 children: new-onset seizures (N=118; group A) versus those with known epilepsy (N=72; group B). At least one diagnostic test was performed on 156 patients (82.1%) (group A, N=104, 88.1%; group B, N=52, 72.2%; P=0.05). In group B, blood levels of antiepileptic drugs were measured in 14 of the 38 patients with SE, of whom six were under dosed. Treatments were: first line, diazepam (group A, 80%; group B, 46%; P<0.001); second line, diazepam (group A, 56%; group B, 34%; P=0.02) or clonazepam (group A, 24%; group B, 46%; P=0.001); third line, phenytoin (group A, 54%; group B, 22%; P<0.001) or clonazepam (group A, 18%; group B, 61%; P<0.001).

CONCLUSION

Diagnostic evaluation and treatment should be individualized for children with known epilepsy.

Genetic and Non-genetic Factors Contributing to the Significant Variation in the Plasma Trough Concentration-to-Dose Ratio of Valproic Acid in Children With Epilepsy

Objective: This study was conducted to evaluate the potential genetic and non-genetic factors contributing to plasma trough concentration-to-dose (C ₀/D) ratio of valproic acid (VPA) in pediatric patients with epilepsy. Study Design: A single-center, retrospective cohort study was performed by collecting data from 194 children aged 1-14 years between May 2018 and November 2018. The oral solution (n = 135) group and the sustained-release (SR) tablet group (n = 59) were defined, and the plasma VPA C ₀ was measured. Twenty-six single-nucleotide polymorphisms (SNPs) were chosen for genotyping with the MassARRAY system. A multiple logistic regression model was used for data analysis. Results: Body weight (BW) and age were positively correlated with the C ₀/D ratio in 194 patients, but the positive correlation disappeared after the patients were divided into oral solution and SR tablet subgroups. The average C ₀/D ratio was significantly increased by 2.11-fold (P = 0.000) in children who took VPA SR tablets compared with children who were administered VPA oral solutions. No significant association between genetic variants and the C ₀/D ratio was found, even for the five well-studied SNPs, namely UGT2B7 G211T, C802T, C161T, T125C, and CYP2C9 ^* 3 A1075C. However, a significant association between the C ₀/D ratio and UGT1A6/9 Del>A (rs144486213) was observed in the VPA oral solution group, but not in the VPA SR tablet group. Conclusions: The dosage forms of sodium valproate, rather than BW, age, or genetic polymorphisms, significantly affected the VPA C ₀/D ratios in pediatric patients with epilepsy. Based on our findings, switching the dosage form between solution and SR tablet should be performed cautiously. Total daily dose adjustment should be considered, and the plasma concentration, seizure-control effect, and adverse drug reaction should also be monitored very closely.

Functional characterization of novel bumetanide derivatives for epilepsy treatment

Temporal lobe epilepsy (TLE) is the most common type of focal epilepsies, affecting approximately 35 million people worldwide. Despite the introduction of numerous novel antiepileptic drugs during the last decades, the proportion of patients with therapy-resistant TLE is still high. As an impaired cellular chloride homeostasis appears involved in disease pathophysiology, bumetanide, an antagonist to Na-K-Cl cotransporters, gained interest as potential therapeutic option. However, bumetanide induces a strong diuretic effect and displays poor penetration across the blood-brain barrier (BBB). To reduce these unwanted effects, we modified the already described BUM690 by exchanging the allyl-into a trifluoro-ethyl group to yield BUM532. Furthermore, we exchanged the nitrogen for oxygen in the trifluoro-ethyl group to yield BUM97. In the intrahippocampal kainic acid mouse model of TLE BUM532 ± phenobarbital (PB), bumetanide ± PB and PB alone significantly reduced hippocampal paroxysmal discharges (HPDs) but not spike trains. By contrast, treatment with BUM97 suppressed HPDs as well as spike trains dose-dependently, more pronounced compared to the other tested compounds and exerted a synergistic anticonvulsant effect with PB. Moreover, at higher doses BUM97 achieved long-lasting reduction of spike trains. In pentylenetetrazole-induced acute seizures only BUM532 combined with a sub-effective dose of PB increased the seizure threshold. No diuretic effects were observed at any dose of the three derivatives. Our data demonstrate the successful optimization of the pharmacological profile of bumetanide and the potential of the improved derivative BUM97 for the treatment of therapy-resistant TLE, in particular in combinatorial drug regimens with a GABA mimetic.

Development and validation of an improved HPLC-UV method for simultaneous determination of lamotrigine and oxcarbazepine and its active metabolite 10,11-dihydro-10-hydroxycarbazepine in human blood plasma and comparison with an UHPLC-MS/MS method

Lamotrigine (LTG) and oxcarbazepine (OXC) are first-line drugs for epilepsy treatment. Their large pharmacokinetics variabilities and relations between efficacy and toxicity and blood plasma concentration require routine monitoring for dose adjustment. In this study, we developed and validated a simple, accurate, and reliable method for simultaneous determination of LTG, OXC and 10,11-dihydro-10-hydroxycarbazepine (MHD) in human blood plasma by high-performance liquid chromatography-ultraviolet detection (HPLC-UV) with a simple one-step protein precipitation using methanol (1% acetic acid) and 15 min elution time under isocratic elution at 1 mL/min. Calibration range was 2.4 to 120 mg/L for LTG, OXC, and MHD. The intra-day and inter-day bias were − 8.84 to 4.18%, and the imprecision was less than 8.08% for all analytes. The internal standard (fluconazole) normalized recovery was 96.30 to 107.69% for LTG, 98.51 to 111.04% for MHD, and 95.04 to 109.86% for OXC. A total of 186 LTG samples and 25 MHD samples were used to evaluate the agreement between HPLC-UV and ultra-performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) by Passing-Bablok regression and Bland-Altman plot. The mean bias and the 95% limits of agreement (95% LOA) of the two measurements were 0.575 mg/L and − 1.238 to 2.387 mg/L for LTG (n = 186) and − 1.222 mg/L and − 8.271 to 5.827 mg/L for MHD (n = 25), which indicated the UV method was comparable with the MS method for LTG and MHD analysis.

Optimizing Management of Medically Responsive Epilepsy

PURPOSE OF REVIEW

This article reviews the management of patients with medically responsive epilepsy, including discussion of factors that may lead to transient breakthrough seizures and patient and physician strategies to maintain freedom from seizures.

RECENT FINDINGS

Imperfect adherence, unanticipated changes in ongoing medical therapy, inadvertent use of proconvulsants or concurrent medications that alter epilepsy medication kinetics, and a variety of seizure precipitants such as stress or sleep deprivation may alter long-term seizure control.

SUMMARY

The majority of patients with epilepsy are medically responsive. Many potential factors may lead to breakthrough seizures in these patients. Identification of these factors, patient education, and use of self-management techniques including mindfulness therapy and cognitive-behavioral therapy may play a role in protecting patients with epilepsy against breakthrough seizures.

Quality improvement in the management of people with epilepsy and intellectual disability: the development of clinical guidance

Introduction: This clinical guidance looks at the specific concerns of delivery of medical treatment for people with epilepsy and intellectual disability (ID). People with ID have not been included in licensing drug trials of AEDs. However, this population has an over-representation of seizure comorbidity, treatment resistance, and polypharmacy while also being vulnerable to not having their views considered.Areas covered: This review summarizes the current most robust evidence available for the use of licensed AEDs in people with epilepsy and ID. The article provides practical evidence-based clinical information to help prescribers choose the most appropriate AED from the drugs discussed. The article highlights other important individualized factors to consider before initiating or changing antiepileptic medication.Expert opinion: A 'traffic light' coding system is applied to commonly used AEDs based on the level of evidence and expert clinical experience. Managing epilepsy in the ID population requires specialist care. Treatment plans need to be holistic and tailored to accommodate an individual's comorbidities, concurrent medications, general health, social and environmental status. There is a need for large quality trial data to assess the most suitable AEDs on seizure control and quality of life in this population with complex needs.

Quality of therapeutic drug monitoring guidelines is suboptimal: an evaluation using the Appraisal of Guidelines for Research and Evaluation II instrument

OBJECTIVES

Although therapeutic drug monitoring (TDM) guidelines are available, systematic evaluations of their methodological quality are scarce. This study aimed to assess the quality of current TDM guidelines using the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument.

STUDY DESIGN AND SETTING

We performed a systematic search to identify the relevant TDM guidelines in PubMed, EMBASE, CNKI, Wan Fang Database, CBM, VIP, four main guideline databases (NICE, NGC, GIN, and WHO guideline databases), and official websites of the governments and societies associated with TDM from the inception date to May 2018. Four independent appraisers rated the quality of each TDM guideline using the AGREE II instrument, and the mean score of each AGREE II item was calculated. The overall agreement among the appraisers was evaluated using the intraclass correlation coefficient (ICC).

RESULTS

Twenty-eight TDM guidelines satisfied the eligibility criteria from among 12,235 references. The overall agreement among the appraisers was substantial (0.700-0.880). The mean scores for the six AGREE II domains were scope and purpose, 67.7% (95% CI, 64.0-71.4%); stakeholder involvement, 39.8% (95% CI, 33.3-46.3%); rigor of development, 36.0% (95% CI, 28.1-43.9%); clarity and presentation, 61.6% (95% CI, 55.7-67.4%); applicability, 30.6% (95% CI, 26.4-34.8%); and editorial independence, 49.2% (95% CI, 40.0-58.6%). The reviewers recommended only four guidelines, and most of the TDM guidelines were rated as "recommended with modifications."

CONCLUSION

Overall, the quality of TDM guidelines is suboptimal according to the evaluation using the AGREE II instrument. The domains of applicability, rigor of development, stakeholder involvement, and editorial independence of the guidelines need to be reported. In addition, guideline developers closely adhering to the AGREE II instrument and the Grading of Recommendations Assessment Development and Evaluation system are required to draft high-quality and reliable TDM guidelines.

Proof-of-concept that network pharmacology is effective to modify development of acquired temporal lobe epilepsy

Epilepsy is a complex network phenomenon that, as yet, cannot be prevented or cured. We recently proposed network-based approaches to prevent epileptogenesis. For proof of concept we combined two drugs (levetiracetam and topiramate) for which in silico analysis of drug-protein interaction networks indicated a synergistic effect on a large functional network of epilepsy-relevant proteins. Using the intrahippocampal kainate mouse model of temporal lobe epilepsy, the drug combination was administered during the latent period before onset of spontaneous recurrent seizures (SRS). When SRS were periodically recorded by video-EEG monitoring after termination of treatment, a significant decrease in incidence and frequency of SRS was determined, indicating antiepileptogenic efficacy. Such efficacy was not observed following single drug treatment. Furthermore, a combination of levetiracetam and phenobarbital, for which in silico analysis of drug-protein interaction networks did not indicate any significant drug-drug interaction, was not effective to modify development of epilepsy. Surprisingly, the promising antiepileptogenic effect of the levetiracetam/topiramate combination was obtained in the absence of any significant neuroprotective or anti-inflammatory effects as indicated by multimodal brain imaging and histopathology. High throughput RNA-sequencing (RNA-seq) of the ipsilateral hippocampus of mice treated with the levetiracetam/topiramate combination showed that several genes that have been linked previously to epileptogenesis, were significantly differentially expressed, providing interesting entry points for future mechanistic studies. Overall, we have discovered a novel combination treatment with promise for prevention of epilepsy.

Determination of unbound valproic acid in plasma using centrifugal ultrafiltration and gas chromatography:Application in TDM

AIM

In order to monitor the free concentration of VPA in plasma, a simple and rapid method needs to be developed.

METHODS

The free fraction of VPA in plasma was obtained by centrifugal ultrafiltration (CF-UF) devices. Cyclohexanecarboxylic acid was used as internal standard. Valproate in plasma was converted to VPA by sulphuric acid acidification, and dichloromethane was used as solvent for extraction. Nitrogen was the carrier gas, the samples were separated by capillary column, and the flame ionization detector was used to detect VPA fragment ions for quantitative analysis.

RESULTS

The assay had good specificity and stability. The linear range of the assay was 0.56-28.11 mg/L. The intra-day and inter-day precision (RSDs) of the assay were all within 15%, and the accuracy (RE) was 2.58%. The recoveries of VPA with three different concentrations were 102.03 ± 1.05, 101.45 ± 2.08 and 102.58 ± 3.38. The results of therapeutic drug monitoring (TDM) in pediatric inpatient group and outpatient group showed significant differences between the two groups (P < 0.001).

CONCLUSION

This assay has low cost and good analytical performance, so it can be developed into a routine TDM method of unbound VPA. We recommend the monitoring of unbound VPA concentration in pediatric inpatients during clinical use of VPA.

Effect of Age-Related Factors on the Pharmacokinetics of Lamotrigine and Potential Implications for Maintenance Dose Optimisation in Future Clinical Trials

BACKGROUND AND AIMS

In this study, we evaluate the performance of allometric concepts to predict the implications of age and size on the pharmacokinetics of lamotrigine, and assess the dose rationale across different age groups from 0.2 to 91 years.

METHODS

An allometrically scaled pharmacokinetic model was developed using adolescent and adult data, taking into account the effect of comedications. Model parameters were then used to extrapolate lamotrigine pharmacokinetics to older adults (> 65 years), children (4-12 years) and infants and toddlers (0.2-2.0 years). In addition, simulations were performed to identify the implication of different doses and dosing regimens for each population, so as to ensure steady-state concentrations within a predefined reference range.

RESULTS

The pharmacokinetics of lamotrigine was best described using a one-compartment model with first-order absorption and elimination. Carbamazepine, phenytoin, and valproic acid changed systemic clearance (CL) by + 76.5, + 129, and - 47.4%, respectively. Allometric principles allowed accurate extrapolation of disposition parameters to older adults and children older than 4 years of age. A maturation function was required to describe changes in exposure in younger patients. Compared with adults, a child aged 1.7 years has a 31.5% higher CL, after correcting for body weight. Patients > 65 years of age showed a decrease in CL of approximately 15%.

CONCLUSION

Population pharmacokinetic models are usually limited to a subgroup of patients, which may mask the identification of factors contributing to interindividual variability. The availability of an integrated model including the whole patient population provides insight into the role of age-related changes in the disposition of lamotrigine, and potential implications for maintenance dose optimisation in any future trials.

TRIAL REGISTRATION

According to GlaxoSmithKline's Clinical Trial Register, data from the GlaxoSmithKline studies LAM100034 and LEP103944, corresponding to ClinicalTrials.gov identifiers NCT00113165 and NCT00264615, used in this work, have been used in previous publications (doi: https://doi.org/10.1212/01.wnl.0000277698.33743.8b , https://doi.org/10.1111/j.1528-1167.2007.01274.x ).

[Clinical Pharmacometrics for Rational Drug Treatment]

Pharmacometrics is the mathematical study of pharmacokinetics, disease progression, and clinical outcomes. One objective of pharmacometrics is to facilitate rational drug treatment in patients, also termed clinical pharmacometrics. In this review, our clinical pharmacometric studies conducted over the last 10 years are discussed. Population pharmacokinetic analysis using therapeutic monitoring data for levetiracetam revealed that oral clearance allometrically scaled to both body weight and estimated glomerular filtration rate can accurately predict clinical data from patients of various ages (pediatric to elderly) with varying renal function. Dosage adjustments based on renal function in the package information are effective in controlling the trough and peak concentrations in similar ranges. In addition, a retrospective pharmacokinetic and pharmacodynamic study revealed that the efficacy of low-dose clobazam therapy was significantly influenced by CYP2C19 polymorphisms. Pharmacokinetic and pharmacodynamic models were successfully built using electronic medical information to explain retrospective international normalized ratio values of prothrombin time before and after catheter ablation in warfarin-treated patients. Simulation studies suggest that more than 20 mg of vitamin K₂ is unnecessary in the preoperative period of catheter ablation. A physiologically based pharmacokinetic model adapted to tacrolimus pharmacokinetic data in patients who underwent living-donor liver transplantation was constructed, and clarified that oral clearance of this drug was affected by CYP3A5 genotypes in both the liver and intestine to the same extent. In conclusion, pharmacometrics is a useful methodology for individualized and optimized drug therapy.

The anti-epileptic drug lamotrigine inhibits the CYP17A1 lyase reaction in vitro

The potential endocrine disrupting effects of the commonly prescribed anti-epileptic drug lamotrigine (LAM) were investigated using the H295R steroidogenic in vitro assay and computational chemistry methods. The H295R cells were exposed to different concentrations of LAM, and a multi-steroid LC-MS/MS method was applied to quantify the amount of secreted steroid hormones. LAM affected several steroid hormones in the steroidogenesis at therapeutic concentrations. All progestagens as well as 11-deoxycorticosterone and corticosterone increased 100-200% with increasing concentrations of LAM suggesting a selective inhibitory effect of LAM on CYP17A1, in particular on the lyase reaction. Recombinant CYP17A1 assay confirmed the competitive inhibition of LAM toward the enzyme with IC50 values of 619 and 764 μM for the lyase and the hydroxylase reaction, respectively. Levels of androstenedione and testosterone decreased at LAM concentrations above the therapeutic concentration range. The ability of LAM to bind to CYP17A1, CYP19A1, and CYP21A2 was investigated using docking and molecular dynamics simulations. This in silico study showed that LAM was able to bind directly to the heme iron in the active site of CYP17A1, but not CYP21A2, thus supporting the results of the in vitro studies. The molecular dynamics simulations also suggested binding of LAM to the heme iron in the CYP19A1 active site. No inhibition of the aromatase enzyme was, however, observed in the H295R assay. This could be due to a sequential effect within the steroidogenesis caused by the inhibition of CYP17A1, which reduced the amounts of androgens available for CYP19A1.

Pharmacokinetic considerations in pediatric pharmacotherapy

Purpose

The changes in physiological functions as children grow and organ systems mature result in pharmacokinetic alterations throughout childhood. These alterations in children result in absorption, distribution, metabolism, and excretion of drugs that are different from those seen in the typical adult diseased population.

Summary

Changes in gastrointestinal motility and gastric pH in neonates and infants affect the absorption rate and bioavailability of drugs. Skin absorption rate and extent can be altered by different skin structures and perfusion in young children. Intramuscular and rectal absorption become less predictable in children due to erratic absorption site perfusion and other factors. Children’s body compositions also differ greatly from that in adults. Water-soluble drugs distribute more extensively in newborns due to larger water content than in older children and adults. Drug elimination and excretion are also affected in pediatric population due to differences in liver and renal function. Immature enzyme development and renal function result in reduced clearance of drugs in young children. There are limited pharmacokinetic data available for many drugs used in children.

Conclusion

Considering the changes in pharmacokinetics in children can help pharmacists optimize the dosing and monitoring of drugs and do the best they can to help this vulnerable population.

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

Objective

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.

Methods

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.

Results

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.

Conclusions

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.