Influence of dronedarone (a class III antiarrhythmic drug) on the anticonvulsant potency of four classical antiepileptic drugs in the tonic-clonic seizure model in mice

Antiseizure Effects of Scoparone, Borneol and Their Impact on the Anticonvulsant Potency of Four Classic Antiseizure Medications in the Mouse MES Model-An Isobolographic Transformation

Numerous botanical drugs containing coumarins and terpenes are used in ethnomedicine all over the world for their various therapeutic properties, especially those affecting the CNS system. The treatment of epilepsy is based on antiseizure medications (ASMs), although novel strategies using naturally occurring substances with confirmed antiseizure properties are being developed nowadays. The aim of this study was to determine the anticonvulsant profiles of scoparone (a simple coumarin) and borneol (a bicyclic monoterpenoid) when administered separately and in combination, as well as their impact on the antiseizure effects of four classic ASMs (carbamazepine, phenytoin, phenobarbital and valproate) in the mouse model of maximal electroshock-induced (MES) tonic-clonic seizures. MES-induced seizures were evoked in mice receiving the respective doses of the tested natural compounds and classic ASMs (when applied alone or in combinations). Interactions for two-drug and three-drug mixtures were assessed by means of isobolographic transformation of data. Polygonograms were used to illustrate the types of interactions occurring among drugs. The total brain content of ASMs was measured in mice receiving the respective drug treatments with fluorescent polarization immunoassay. Scoparone and borneol, when administered alone, exerted anticonvulsant properties in the mouse MES model. The two-drug mixtures of scoparone with valproate, borneol with phenobarbital and borneol with valproate produced synergistic interactions in the mouse MES model, while the remaining tested two-drug mixtures produced additivity. The three-drug mixtures of scoparone + borneol with valproate and phenobarbital produced synergistic interactions in the mouse MES model. Verification of total brain concentrations of valproate and phenobarbital revealed that borneol elevated the total brain concentrations of both ASMs, while scoparone did not affect the brain content of these ASMs in mice. The synergistic interaction of scoparone with valproate observed in the mouse MES model is pharmacodynamic in nature. Borneol elevated the brain concentrations of the tested ASMs, contributing to the pharmacokinetic nature of the observed synergistic interactions with valproate and phenobarbital in the mouse MES model.

Effects of Antiarrhythmic Drugs on Antiepileptic Drug Action-A Critical Review of Experimental Findings

Severe cardiac arrhythmias developing in the course of seizures increase the risk of SUDEP (sudden unexpected death in epilepsy). Hence, epilepsy patients with pre-existing arrhythmias should receive appropriate pharmacotherapy. Concomitant treatment with antiarrhythmic and antiseizure medications creates, however, the possibility of drug–drug interactions. This is due, among other reasons, to a similar mechanism of action. Both groups of drugs inhibit the conduction of electrical impulses in excitable tissues. The aim of this review was the analysis of such interactions in animal seizure models, including the maximal electroshock (MES) test in mice, a widely accepted screening test for antiepileptic drugs.

Amiodarone Enhances Anticonvulsive Effect of Oxcarbazepine and Pregabalin in the Mouse Maximal Electroshock Model

Accumulating experimental studies show that antiarrhythmic and antiepileptic drugs share some molecular mechanisms of action and can interact with each other. In this study, the influence of amiodarone (a class III antiarrhythmic drug) on the antiseizure action of four second-generation antiepileptic drugs was evaluated in the maximal electroshock model in mice. Amiodarone, although ineffective in the electroconvulsive threshold test, significantly potentiated the antielectroshock activity of oxcarbazepine and pregabalin. Amiodarone, given alone or in combination with oxcarbazepine, lamotrigine, or topiramate, significantly disturbed long-term memory in the passive-avoidance task in mice. Brain concentrations of antiepileptic drugs were not affected by amiodarone. However, the brain concentration of amiodarone was significantly elevated by oxcarbazepine, topiramate, and pregabalin. Additionally, oxcarbazepine and pregabalin elevated the brain concentration of desethylamiodarone, the main metabolite of amiodarone. In conclusion, potentially beneficial action of amiodarone in epilepsy patients seems to be limited by neurotoxic effects of amiodarone. Although results of this study should still be confirmed in chronic protocols of treatment, special precautions are recommended in clinical conditions. Coadministration of amiodarone, even at low therapeutic doses, with antiepileptic drugs should be carefully monitored to exclude undesired effects related to accumulation of the antiarrhythmic drug and its main metabolite, desethylamiodarone.

Dronedarone (a multichannel blocker) enhances the anticonvulsant potency of lamotrigine, but not that of lacosamide, pregabalin and topiramate in the tonic-clonic seizure model in mice

Accumulating experimental evidence indicates that some recently licensed antiarrhythmic drugs, including dronedarone (a multichannel blocker) play a crucial role in initiation of seizures in both, in vivo and in vitro studies. Some of these antiarrhythmic drugs elevate the threshold for maximal electroconvulsions and enhance the anticonvulsant potency of classical antiepileptic drugs in preclinical studies. This study was aimed at determining the influence of dronedarone (an antiarrhythmic drug) on the anticonvulsant potency of four novel antiepileptic drugs (lacosamide, lamotrigine, pregabalin and topiramate) in the maximal electroshock-induced seizure model in mice. To exclude any potential pharmacokinetic contribution of dronedarone to the observed interactions, total brain concentrations of antiepileptic drugs were measured. Dronedarone (50 mg/kg, i.p.) significantly enhanced the anticonvulsant potency of lamotrigine, by reducing its ED₅₀ value from 7.67 mg/kg to 4.19 mg/kg (P < 0.05), in the maximal electroshock-induced seizure test in mice. On the contrary, dronedarone (50 mg/kg, i.p.) did not affect the anticonvulsant properties of lacosamide, pregabalin or topiramate in the maximal electroshock-induced seizure test in mice. Measurement of total brain concentrations of lamotrigine revealed that dronedarone did not significantly alter total brain concentrations of lamotrigine in experimental animals. Additionally, the combination of dronedarone with pregabalin significantly impaired motor coordination in animals subjected to the chimney test. In contrast, the combinations of other studied antiepileptic drugs with dronedarone had no negative influence on motor coordination in mice. It is advisable to combine dronedarone with lamotrigine to enhance the anticonvulsant potency of the latter drug. The combinations of dronedarone with lacosamide, pregabalin and topiramate resulted in neutral interactions in the maximal electroshock-induced seizure test in mice. However, a special caution is advised to patients receiving both, pregabalin and dronedarone due to some possible adverse effects that might occur with respect to motor coordination.