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Novel Antiepileptic Drugs (novel + antiepileptic_drug)
Selected AbstractsAnticonvulsant Efficacy of Topiramate in Phenytoin-Resistant Kindled RatsEPILEPSIA, Issue 4 2000Elke Reissmüller Summary: Purpose: We evaluated the anticonvulsant efficacy of topiramate (TPM), a structurally novel antiepileptic drug (AED), in amygdala kindled rats that had been preselected with respect to their response to phenytoin (PHT). Methods: Anticonvulsant response was tested by determining the afterdischarge threshold (ADT;i.e., a sensitive measure for drug effects on focal seizure activity). By repeated testing with the PHT prodrug fosphenytoin (FOS) three groups of kindled rats were separated: rats in which consistent anticonvulsant effects were obtained (PHT responders), rats that showed no anticonvulsant response (PHT nonresponders), and rats with variable responses (variable PHT responders). The latter, largest group was used to evaluate at which doses and pretreatment times TPM exerted significant anticonvulsant effects on ADT. For this purpose, TPM was tested at four doses (20, 40, 80, 160 mg/kg i.p.) and two pretreatment times (1 and 4 h). The most effective treatment protocol was then used for TPM testing in PHT responders and nonresponders. Results: TPM proved to be an effective AED in the kindling model. At 40 mg/kg, significant ADT increases were obtained after both 1 and 4 h after administration. In addition to the effect on focal seizure threshold, seizure severity and duration recorded at ADT were decreased by TPM, indicating that this drug acts on both seizure threshold and seizure spread. In PHT nonresponders, TPM significantly increased ADT, which is in line with its proven efficacy in patients with refractory partial epilepsy in whom phenytoin has failed. However, TPM was more efficacious in increasing ADT in PHT responders than in nonresponders, substantiating that the difference between these groups of kindled rats extends to other AEDs. Repeated testing of kindled rats with TPM indicated that, similar to PHT, there are individual kindled rats without anticonvulsant response to TPM (i.e., TPM nonresponders). Conclusions: The data of this study substantiate that PHT nonresponders are a unique model for the search of new AEDs with improved efficacy in refractory partial epilepsy. [source] RESEARCH PAPER: The antihyperalgesic effect of levetiracetam in an inflammatory model of pain in rats: mechanism of actionBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2010A Micov BACKGROUND AND PURPOSE Levetiracetam, a novel antiepileptic drug, has recently been shown to have antinociceptive effects in various animal models of pain. The purpose of this study was to investigate the antihyperalgesic effect of levetiracetam and its mechanism of action, by examining the involvement of GABAergic, opioidergic, 5-hydroxytryptaminergic (5-HTergic) and adrenergic systems in its effect, in a rat model of inflammatory pain. EXPERIMENTAL APPROACH Rats were intraplantarly injected with the pro-inflammatory compound carrageenan. A paw pressure test was used to determine: (i) the effect of levetiracetam on carrageenan-induced hyperalgesia; and (ii) the effects of bicuculline (selective GABAA receptor antagonist), naloxone (non-selective opioid receptor antagonist), methysergide (non-selective 5-HT receptor antagonist) and yohimbine (selective ,2 -adrenoceptor antagonist) on the antihyperalgesic action of levetiracetam. RESULTS Levetiracetam (10,200 mg·kg,1; p.o.) significantly reduced, in a dose-dependent manner, the inflammatory hyperalgesia induced by carrageenan. The antihyperalgesic effect of levetiracetam was significantly decreased after administration of bicuculline (0.5,2 mg·kg,1; i.p.), naloxone (1,3 mg·kg,1; i.p.), methysergide (0.25,1 mg·kg,1; i.p.) and yohimbine (1,3 mg·kg,1; i.p.). CONCLUSIONS AND IMPLICATIONS These results show that levetiracetam produced antihyperalgesia which is at least in part mediated by GABAA, opioid, 5-HT and ,2 -adrenergic receptors, in an inflammatory model of pain. The efficacy of levetiracetam in this animal model of inflammatory pain suggests that it could be a potentially important agent for treating inflammatory pain conditions in humans. [source] Intracellular Calcium Increase in Epileptiform Activity: Modulation by Levetiracetam and LamotrigineEPILEPSIA, Issue 7 2004Antonio Pisani Summary:,Purpose: Alterations in neuronal calcium (Ca2+) homeostasis are believed to play an essential role in the generation and propagation of epileptiform events. Levetiracetam (LEV) and lamotrigine (LTG), novel antiepileptic drugs (AEDs), were tested on epileptiform events and the corresponding elevations in intracellular Ca2+ concentration ([Ca2+]i) recorded from rat neocortical slices. Methods: Electrophysiological recordings were performed from single pyramidal neurons from a slice preparation. Spontaneous epileptiform events consisting of long-lasting, repetitive paroxysmal depolarization shifts (PDSs) and interictal spike activity were induced by reducing the magnesium concentration from the solution and by adding bicuculline and 4-aminopyridine. Simultaneously, microfluorimetric measurements of [Ca2+]i were performed. Optical imaging with Ca2+ indicators revealed a close correlation between Ca2+ transients and epileptiform events. Results: Both LEV and LTG were able to reduce both amplitude and duration of PDSs, as well as the concomitant elevation in [Ca2+]i, in a dose-dependent fashion. Whole-cell patch-clamp recordings from isolated neocortical neurons revealed that LEV significantly reduced N-, and partially P/Q-type high-voltage-activated (HVA) Ca2+ currents, whereas sodium currents were unaffected. Interestingly, the inhibitory effects of LEV were mimicked and occluded by LTG or by a combination of ,-conotoxin GVIA and ,-agatoxin IVA, selective blockers of N- and P/Q-type HVA channels, respectively, suggesting a common site of action for these AEDs. Conclusions: These results demonstrate that large, transient elevations in neuronal [Ca2+]i correlate to epileptiform discharges. The antagonistic effects of LEV and LTG on [Ca2+]i overload might represent the basis for their anticonvulsant efficacy and could preserve neuronal viability. [source] Antiepileptic Drugs in Migraine PreventionHEADACHE, Issue 2001Ninan T. Mathew MD Migraineurs may continue to experience attacks, despite daily use of one or more agents from a wide range of drugs, including , -blockers, calcium channel blockers, serotonin antagonists, tricyclic antidepressants, monoamine oxidase inhibitors, and antiepileptic agents. Divalproex sodium is the only antiepileptic drug approved for migraine prevention. Gabapentin, topiramate, and other antiepileptic agents are being evaluated for migraine prevention and treatment. Prospective, double-blind, placebo-controlled clinical trials of divalproex, gabapentin, and topiramate for migraine prevention generally were composed of a prospective baseline period, a dose titration period, and a fixed-dose treatment period. The primary efficacy variable was a reduction in the 28-day frequency of migraine headache. Patients receiving divalproex for 12 weeks at doses up to 1500 mg/day achieved significant decreases in the migraine frequency (P<.05), corresponding to reductions of 30% to 40% compared with baseline. Nearly half of the divalproex-treated patients had a 50% or more reduction from baseline in headache frequencies (P.05). Asthenia, vomiting, somnolence, tremor, and alopecia were common adverse events associated with divalproex. Significant reductions in migraine frequency were also observed with gabapentin (1800 to 2400 mg/day) when compared with placebo (P<.01), and nearly half of all patients treated at the highest dose experienced a reduction in headache rate of 50% or more. Somnolence was the most commonly reported adverse event among the gabapentin-treated patients. Two single-center, double-blind, placebo-controlled clinical trials evaluated topiramate for migraine prevention. A lower 28-day migraine frequency was seen during 18 weeks of administration at a maximum daily dose of 200 mg (P = .09). In a second study, a significantly lower mean 28-day migraine frequency was observed during 16 weeks of treatment with topiramate (P = .0015). Mean reduction in migraine frequency was also significantly greater in topiramate-treated patients (P = .0037). Paresthesias, diarrhea, somnolence, and altered taste were commonly reported adverse events in the topiramate-treated patients. Unlike some patients given divalproex or gabapentin, some given topiramate reported weight loss. Large, double-blind, placebo-controlled trials may prove the effectiveness of novel antiepileptic drugs in migraine prevention. [source] Epilepsy and intellectual disabilityJOURNAL OF INTELLECTUAL DISABILITY RESEARCH, Issue 5 2000C. Bowley Abstract A Medline and Psychline literature review of epilepsy in people with intellectual disability was performed. The review has highlighted the importance of the impact of epilepsy on the lives of individuals and their families, affecting physical morbidity, leading to an increased mortality and increasing the care-giving burden. Interventions with a strong evidence base are mainly pharmacological with an increasing body of work on the novel antiepileptic drugs. Surprisingly little research exists into the quality of service provision for this population. The authors suggest three areas for future work: (1) an increasing application of research methodologies such as direct observation and qualitative studies into this field; (2) an exploration of the broad impact of treatment and (3) the possibility that epilepsy is a barrier to care provision. [source] | ||||||||||