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.

Epilepsy and pregnancy: identifying risks

Pregnancy is a time of physical, physiological and psychological challenge. For women with epilepsy, as well as its potential for joy and fulfilment, pregnancy may bring additional risks and difficulties. Clinicians must anticipate and prevent these complications, ensuring that pregnancy, delivery and motherhood proceed without obstetric or medical complications, using available evidence to balance individual risks of undertreatment and overtreatment. Here we review epilepsy management in pregnancy, identifying some of the known effects of epilepsy and its treatment on gestation, fetal malformation, delivery, and neurocognitive and behavioural development. We outline strategies to reduce obstetric and fetal complications in women with epilepsy, while recognising the sometimes competing need to maintain or improve seizure control. We reinforce the importance of identifying those at highest risk, who may require additional measures or safeguards.

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.

Perampanel Serum Concentrations in Adults With Epilepsy: Effect of Dose, Age, Sex, and Concomitant Anti-Epileptic Drugs

BACKGROUND

Perampanel (PMP), a noncompetitive α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) glutamate receptor antagonist, is a novel anti-epileptic drug (AED) licensed for the adjunctive treatment of focal and generalized epilepsy. There is limited information on PMP's pharmacokinetics and drug interaction characteristics with concomitant AEDs. We have investigated the effects of PMP dose, age, sex, and coprescribed AEDs on serum PMP concentrations.

METHODS

We used the database of a therapeutic drug monitoring unit at a tertiary epilepsy referral center to identify patients who had PMP as part of their treatment and extracted clinical information from their medical notes. Sera PMP concentrations were determined using liquid chromatography/mass spectroscopy.

RESULTS

In total, 160 sera from 107 patients (66 females) aged 18-70 years and weighing 40-125 kg were identified. They were prescribed a median PMP dose of 6 mg/d (range 2-12 mg/d) and were coprescribed a variety of AEDs, including enzyme-inducing [carbamazepine (CBZ) and oxcarbazepine (OXC)] and enzyme-inhibiting (valproic acid) AEDs. A linear relationship was observed between PMP dose and serum concentrations (r = 0.714, P < 0.0005). Sex and age were found not to influence PMP serum concentration. Enzyme-inducing AEDs dose-dependently decreased PMP concentrations, with CBZ and OXC decreasing mean values by 69% and 37%, respectively. In contrast, although topiramate and phenytoin also decreased mean PMP concentrations by 18% and 13%, respectively, these changes did not achieve statistical significance.

CONCLUSIONS

PMP exhibits a linear dose-concentration relationship, with serum PMP concentrations being age and sex independent. CBZ and OXC can significantly decrease PMP concentrations, probably through an induction of CYP3A4-mediated metabolism.

The Impact of Pharmacokinetic Interactions With Eslicarbazepine Acetate Versus Oxcarbazepine and Carbamazepine in Clinical Practice

BACKGROUND

Eslicarbazepine acetate (ESL) is a new anti-epileptic drug (AED) chemically related to oxcarbazepine (OXC) and carbamazepine (CBZ) and is increasingly used in clinical practice. The purpose of the study was to investigate 2-way pharmacokinetic interactions between ESL and other AEDs as compared to OXC and CBZ.

METHODS

Anonymous data regarding age, gender, use of AEDs, daily doses and serum concentration measurements of ESL, OXC, CBZ and lamotrigine (LTG) and other AEDs were retrieved from 2 therapeutic drug monitoring (TDM) databases in Norway. Drugs were categorized according to their known potential for interactions. Concentration/dose (C/D) ratios were calculated.

RESULTS

Data from 1100 patients were available. The C/D ratios of ESL and OXC were unchanged in combination with enzyme-inducing AEDs or valproate (VPA). The C/D ratio of CBZ decreased by 40% and 22% in combination with other enzyme-inducing AEDs or VPA, respectively, pointing to an increased clearance. ESL demonstrated no significant enzyme-inducing effect on LTG metabolism although there was a 20% and 34% decrease in the C/D ratio of LTG in combination with OXC and CBZ, respectively.

CONCLUSIONS

Possible pharmacokinetic interactions have been studied for ESL as compared to OXC and CBZ. The pharmacokinetics of ESL is not affected by enzyme-inducing AEDs or VPA and does not affect the metabolism of LTG in contrast to OXC and CBZ. The study demonstrates the value of using TDM databases to explore the potential for pharmacokinetic interactions of new AEDs.

Proconvulsant effects of antidepressants - What is the current evidence?

Antidepressant drugs may have proconvulsant effects. Psychiatric comorbidity in epilepsy is common. Prescribers might be reluctant to initiate treatment with antidepressants in fear of seizure aggravation. The purpose of this review was to focus upon the current evidence for proconvulsant effects of antidepressants and possible clinical implications. Most antidepressants are regarded as safe and may be used in patients with epilepsy, such as the newer serotonin and/or noradrenaline reuptake inhibitors. Four older drugs should, however, be avoided or used with caution; amoxapine, bupropion, clomipramine and maprotiline. Proconvulsant effects are concentration-related. Optimization of drug treatment includes considerations of pharmacokinetic variability to avoid high serum concentrations of the most proconvulsant antidepressants. The risk of seizures is regarded as small and should, therefore, not hamper the pharmacological treatment of depression in people with epilepsy.

Lacosamide serum concentrations in adult patients with epilepsy: the influence of gender, age, dose, and concomitant antiepileptic drugs

OBJECTIVE

Lacosamide (LCM), a new antiepileptic drug (AED) approved as adjunctive therapy for the treatment of patients with partial-onset seizures, has limited pharmacokinetic and drug interaction data. The main objectives of the present study were to investigate the effects of dose, age, gender, and hepatic enzyme-inducing AEDs on the pharmacokinetics of LCM as assessed by steady state serum LCM values.

METHODS

An LCM AED therapeutic drug monitoring database was analyzed with regard to LCM serum concentrations and other relevant patient and AED drug information. One hundred twenty eight sera were identified. These were collected from 68 women and 61 men aged 19-66 years, who were prescribed a median LCM dose of 300 mg (range 50-600 mg).

RESULTS

Serum LCM concentrations were observed in the following main groupings: LCM monotherapy (n = 5), LCM with nonenzyme-inducing AEDs (n = 50), LCM with enzyme-inducing AEDs (n = 49), LCM with valproic acid (n = 20), and LCM with enzyme-inducing AEDs plus valproic acid (n = 4). Analysis of variance showed a correlation of dose with LCM concentrations (r = 0.53, P < 0.001), and women had statistically higher mean LCM concentration than did men, 37.2 ± 23.6 versus 26.8 ± 12.9 μmol/L (P = 0.001). Serum LCM concentrations were significantly lower (P = 0.002) in the enzyme-inducing AED group (carbamazepine and phenytoin) compared with the LCM monotherapy group and the nonenzyme-inducing group, 23.5 ± 11.0, 34.5 ± 7.7, and 32.7 ± 17.9 μmol/L, respectively.

CONCLUSIONS

Serum LCM concentrations increased dose dependently, were age independent, and were higher in women compared with men. Carbamazepine and phenytoin can significantly decrease serum LCM concentrations, probably via induction of LCM metabolism.

Prevalence and cost of epilepsy in Sweden--a register-based approach

OBJECTIVES

To estimate the prevalence of epilepsy, costs associated with in- and outpatient care, drug utilization and productivity losses due to epilepsy in Sweden for the years 2005 and 2011.

METHODS

Cost components were calculated using registry data on inpatient- and outpatient-care utilization, drug sales and early pensions granted due to permanent disability and mortality. Moreover, by cross-identification of information in healthcare and pharmaceutical registries, we were able to distinguish between pharmaceuticals prescribed for epilepsy and non-epilepsy indications.

RESULTS

The prevalence of epilepsy was estimated at 0.62% in 2005 and 0.88% in 2011. The total cost of epilepsy increased during the same period, while the per-patient cost decreased from €2929 to €1729. Direct medical costs accounted for about 36% of the estimated total cost in 2005 and 60% in 2011. The estimated healthcare cost due to epilepsy as a share of total healthcare costs for all illnesses was about the same in 2005 as in 2011 (0.2%), while the corresponding pharmaceutical cost increased from about 0.5% in 2005 to almost 1% in 2011.

CONCLUSIONS

The per-patient cost of epilepsy is substantial, implying a significant aggregated cost incurred on society (despite a prevalence < 1%). Our results suggest that the per-patient pharmaceutical utilization increased, while the per-patient physician visits and hospitalizations decreased, between 2005 and 2011. Moreover, we demonstrate that the 2005 prevalence measure was underestimated the true prevalence in 2005.

Impact of pregnancy on zonisamide pharmacokinetics in rabbits

Pregnancy is associated with various physiological changes which may lead to significant alterations in the pharmacokinetics of many drugs. The present study was aimed to investigate the potential effects of pregnancy on the pharmacokinetic profile of zonisamide (ZNM) in the rabbit. Seven female rabbits were used in this study. The pregnant and nonpregnant rabbits received ZNM orally at a dose of 10 mg/kg and blood samples were collected from the animals just before receiving the drug and then serially for up to 24 h. The plasma samples were analyzed using tandem mass spectrometric method. Following a single oral dose of ZNM to the rabbits, the mean values of ZNM plasma concentrations at different times were consistently low in pregnant compared to nonpregnant rabbits. The mean values of ZNM's Cmax and AUC0-∞ were significantly (P < 0.05) decreased, whereas the CL/F exhibited substantial increase (P < 0.05) in pregnant compared to nonpregnant rabbits. Tmax, t1/2abs, t1/2el, MRT, and Vd/F showed no significant differences between the two groups. The present study demonstrates that pregnancy decreased ZNM plasma concentrations in rabbits and that the decrease could be due to decreased extent of gastrointestinal absorption, induced hepatic metabolism, or enhanced renal elimination of the drug.

Epilepsy, cognition, and neuropsychiatry (Epilepsy, Brain, and Mind, part 2)

Epilepsy is, of course, not one disease but rather a huge number of disorders that can present with seizures. In common, they all reflect brain dysfunction. Moreover, they can affect the mind and, of course, behavior. While animals too may suffer from epilepsy, as far as we know, the electrical discharges are less likely to affect the mind and behavior, which is not surprising. While the epileptic seizures themselves are episodic, the mental and behavioral changes continue, in many cases, interictally. The episodic mental and behavioral manifestations are more dramatic, while the interictal ones are easier to study with anatomical and functional studies. The following extended summaries complement those presented in Part 1.