Anti-Epileptic Drug Combination Efficacy in an In Vitro Seizure Model – Phenytoin and Valproate, Lamotrigine and Valproate

Abstract

In this study, we investigated the relative efficacy of different classes of commonly used anti-epileptic drugs (AEDs) with different mechanisms of action, individually and in combination, to suppress epileptiform discharges in an in vitro model. Extracellular field potential were recorded in 450 μm thick transverse hippocampal slices prepared from juvenile Wistar rats, in which “epileptiform discharges” (ED’s) were produced with a high-K+ (8.5 mM) bicarbonate-buffered saline solution. Single and dual recordings in stratum pyramidale of CA1 and CA3 regions were performed with 3–5 MΩ glass microelectrodes. All drugs—lamotrigine (LTG), phenytoin (PHT) and valproate (VPA)—were applied to the slice by superfusion at a rate of 2 ml/min at 32°C. Effects upon frequency of ED’s were assessed for LTG, PHT and VPA applied at different concentrations, in isolation and in combination. We demonstrated that high-K+ induced ED frequency was reversibly reduced by LTG, PHT and VPA, at concentrations corresponding to human therapeutic blood plasma concentrations. With a protocol using several applications of drugs to the same slice, PHT and VPA in combination displayed additivity of effect with 50μM PHT and 350μM VPA reducing SLD frequency by 44% and 24% individually (n = 19), and together reducing SLD frequency by 66% (n = 19). 20μM LTG reduced SLD frequency by 32% and 350μM VPA by 16% (n = 18). However, in combination there was a supra-linear suppression of ED’s of 64% (n = 18). In another independent set of experiments, similar results of drug combination responses were also found. In conclusion, a combination of conventional AEDs with different mechanisms of action, PHT and VPA, displayed linear additivity of effect on epileptiform activity. More intriguingly, a combination of LTG and VPA considered particularly efficacious clinically showed a supra-additive suppression of ED’s. This approach may be useful as an in vitro platform for assessing drug combination efficacy.

Dimethylethanolamine Decreases Epileptiform Activity in Acute Human Hippocampal Slices in vitro

“…In our approach using a modified submerged chamber, we mostly observed burst activity (spike and burst activity) described before as interictal-like (Remy et al, 2003; Gabriel et al, 2004; Sandow et al, 2015; Reyes-Garcia et al, 2018) and standing in contrast to ictal discharges lasting >10 s. Brückner and Heinemann (2000) suggested that AEDs applied in brain slices (of non-epileptic animals) rather inhibit ictal but not interictal activity. Other animal studies in vitro , however, demonstrated a robust decrease in interictal activity in the hippocampus upon AED application (Fueta and Avoli, 1992; Holtkamp et al, 2017; Taing et al, 2017), which was comparable to our results with LAC and DMEA. We show that burst activity was sensitive to the approved antiepileptic LAC, indicating that our experimental setting is capable of validating and possibly predicting antiepileptic efficacy for drug development.…”

The influence of concomitant antiepileptic drugs on lamotrigine serum concentrations in Northwest Chinese Han population with epilepsy

“…In our hospital, The regimen of LTG + VPA is the most common treatment, Taing et al [29] also pointed out that a combination of LTG and VPA was considered particularly efficacious clinically showed a supra-additive suppression of ED’s, it would be the most common treatment. Gidal et al [30] reported that VPA inhibited the clearance of LTG at a low dose (125 mg/d) and a very low concentration (6.5 μg/mL).…”

The role of chronobiology in drug-resistance epilepsy: The potential use of a variability and chronotherapy-based individualized platform for improving the response to anti-seizure drugs

“…ASD is selected based on the basic principles of epilepsy, and on sex, fertility, age, body weight, drug interactions, and comorbidities. Pharmacological synergistic effects generated by the combination of valproic acid (VPA) and lamotrigine, or the addition of subsequent drugs has a small likelihood of inducing remission [37][38][39][40]. Early surgery in patients with DRE increases the likelihood of post-surgery remission [41].…”