Factors in Variability of Serial Gabapentin Concentrations in Elderly Patients with Epilepsy

Pharmacokinetic Variability of Sulthiame: The Impact of Age, Drug-Drug Interactions, and Biochemical Markers of Toxicity in Patients with Epilepsy

PURPOSE

Sulthiame is an antiseizure medication increasingly used for epilepsy. The aim of this study was to investigate the pharmacokinetic variability of sulthiame in children and adults with epilepsy with respect to age, comedication, dose, serum concentration, and biochemical markers of toxicity in a clinical setting.

METHOD

Retrospective quantitative data from the therapeutic drug monitoring (TDM) database at the Section for Clinical Pharmacology, the National Center for Epilepsy, Norway (2015-2021), were used.

RESULTS

TDM data from 326 patients (127 female/199 male) were included [mean age, 11.4 (range 2-44) years; mean weight, 41 (range 14-109) kg]. Interindividual pharmacokinetic variability in the concentration/(dose/body weight) (C/(D/kg)) ratio was 16-fold; intraindividual variability was up to 8-fold (coefficient of variation = 10%-78%). Young children (younger than 6 years) had a significantly lower C/(D/kg) ratio than older age groups ( P < 0.05). Various comedications did not significantly affect the C/(D/kg) ratio, possibly owing to the small sample size. However, CYP2C19-mediated inhibition by sulthiame was indicated because patients using clobazam and sulthiame (n = 28) had a 3.5-fold higher N-desmethylclobazam C/(D/kg) ratio than those using neutral comedication (n = 45; P < 0.001). Patients with pH values below the adjusted normal range (7.32-7.42; n = 15) had a 33% higher sulthiame concentration than those with normal pH values (n = 22; P < 0.05). Blood gas measurements, especially pH, may serve as markers of toxicity and can be used in combination with clinical data when toxicity is suspected.

CONCLUSIONS

This study revealed the extensive intraindividual and interindividual pharmacokinetic variability of sulthiame, with age as a contributing factor. Sulthiame has clinically relevant interactions with clobazam. The use of TDM and pH as a biochemical marker may contribute to individualized and safe sulthiame treatment.

Alzheimer's Disease and Epilepsy: A Perspective on the Opportunities for Overlapping Therapeutic Innovation

Early-onset Alzheimer's disease (AD) is associated with variants in amyloid precursor protein (APP) and presenilin (PSEN) 1 and 2. It is increasingly recognized that patients with AD experience undiagnosed focal seizures. These AD patients with reported seizures may have worsened disease trajectory. Seizures in epilepsy can also lead to cognitive deficits, neuroinflammation, and neurodegeneration. Epilepsy is roughly three times more common in individuals aged 65 and older. Due to the numerous available antiseizure drugs (ASDs), treatment of seizures has been proposed to reduce the burden of AD. More work is needed to establish the functional impact of seizures in AD to determine whether ASDs could be a rational therapeutic strategy. The efficacy of ASDs in aged animals is not routinely studied, despite the fact that the elderly represents the fastest growing demographic with epilepsy. This leaves a particular gap in understanding the discrete pathophysiological overlap between hyperexcitability and aging, and AD more specifically. Most of our preclinical knowledge of hyperexcitability in AD has come from mouse models that overexpress APP. While these studies have been invaluable, other drivers underlie AD, e.g. PSEN2. A diversity of animal models should be more frequently integrated into the study of hyperexcitability in AD, which could be particularly beneficial to identify novel therapies. Specifically, AD-associated risk genes, in particular PSENs, altogether represent underexplored contributors to hyperexcitability. This review assesses the available studies of ASDs administration in clinical AD populations and preclinical studies with AD-associated models and offers a perspective on the opportunities for further therapeutic innovation.

Long-term follow-up with therapeutic drug monitoring of antiepileptic drugs in patients with juvenile myoclonic epilepsy

BACKGROUND AND PURPOSE

Patients with juvenile myoclonus epilepsy (JME) may experience uncontrolled seizures and challenges regarding adherence. Implementation of therapeutic drug monitoring (TDM) may contribute to individualization of the therapy with antiepileptic drugs (AEDs). The purpose of this study was to investigate how the treatment of patients with JME is monitored and to demonstrate pharmacokinetic variability within and between patients with a long-term TDM approach.

METHOD

Retrospective data from patients with JME from the TDM-database at Drammen Hospital and the National Center for Epilepsy in Norway (2007-2018) were included.

RESULTS

Data from 80 of 90 patients with JME using AEDs with TDM measurements was included (88%, 49/31 women/men aged 14-39). One third (27, 33%) was seizure free, 19 (24%) had generalized tonic-clonic seizures, and 53 (66%) myoclonic seizures during the last year. The most common AEDs measured included lamotrigine, valproate, and levetiracetam. Long-term TDM demonstrated variability over time expressed as intra-patient median values and inter-patient ranges of 19% (7-47) for valproate, 43% (10-83) for lamotrigine and 35% (6-111) for levetiracetam. Fifteen pecent (83/563) of serum concentrations were below the reference ranges and clould be due to variable adherence. Comedication with valproate for lamotrigine and pregnancy contributed to variability. The applicability is illustrated in a case of 10 years' follow-up in a young woman.

CONCLUSION

There was extensive pharmacokinetic variability of AEDs in and between patients with JME. A long-term TDM approach may contribute to closer monitoring of patients with JME and be used as a practical tool during clinical consultations.