Epilepsia
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Review Randomized Controlled Trial Clinical Trial
Monotherapy trials with gabapentin for partial epilepsy.
The efficacy and safety of gabapentin as monotherapy for treatment of partial onset seizures were evaluated in three large multicenter, double-blind, parallel-group, dose-controlled trials. In the first trial, 275 outpatients with refractory partial epilepsy maintained on stable doses of one or two antiepileptic drugs (AEDs) were switched to gabapentin (GBP) monotherapy at 600 mg, 1200 mg, or 2400 mg daily. Patients were required to exit the 26-week double-blind phase of the study if they experienced worsening of seizure frequency. ⋯ The completion rate for the CBZ group (37%) was similar to that of the GBP 900-mg (39%) and 1800-mg (38%) groups. Patients receiving CBZ had a higher withdrawal rate because of adverse events compared with the GBP 900-mg and 1800-mg groups. The results of these trials provide good evidence of the efficacy and safety of GBP as monotherapy for the treatment of partial-onset seizures.
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For decades, antiepileptic drugs (AEDs) have been used to treat a variety of nonepileptic conditions such as chronic pain, psychiatric disorders, and movement disorders. As indicated by recent published reports, gabapentin, a relatively new AED, is useful for treating a wide range of neurologic and psychiatric conditions. Although its exact mechanism of action has yet to be determined, gabapentin is likely to have multiple effects. ⋯ It has also been reported effective as therapy for several psychiatric disorders, most notably bipolar disorder. In addition, review of the published literature reveals the usefulness of gabapentin in movement disorders, migraine prophylaxis, and cocaine dependence. Future clinical studies will provide further insight into the range of conditions for which gabapentin is effective.
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Gabapentin, in clinical use since 1993, is indicated as an adjunctive antiepileptic drug (AED) for treatment of complex partial seizures, with or without secondary generalization, in patients over 12 years of age. Although several cellular actions have been described in the literature, the molecular mechanism(s) of action responsible for the anticonvulsant effect of gabapentin has not been conclusively determined. It is likely that gabapentin has multiple concentration-dependent actions that combine in a unique manner to produce antiepileptic efficacy. ⋯ To date, nearly 3 million patients have been treated in studies and in open use without causal relationship to a specific life-threatening organ toxicity. Seizure control superior to that observed in well-controlled trials has been reported at higher doses used in clinical practice and in studies. Therefore, gabapentin dosing must be optimized on an individual basis to achieve an adequate trial of the drug and obtain the best seizure control.
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Review Comparative Study
Comparative anticonvulsant and mechanistic profile of the established and newer antiepileptic drugs.
Since 1993, several new antiepileptic drugs (AEDs) have been introduced for management of partial seizures. Like the established AEDs, the new drugs are believed to exert their anticonvulsant action through enhancement of inhibitory-mediated neurotransmission, or reduction of excitatory-mediated neurotransmission, or by a combination of both. Among the new drugs, vigabatrin (VGB) and tiagabine (TGB) are unique in that they were derived from mechanistic-based drug discovery programs designed to identify effective AEDs that inhibit the metabolism and reuptake of the inhibitory neurotransmitter GABA, respectively. ⋯ FBM and TPM differ from both the established and newer AEDs in their ability to modulate NMDA- and AMPA/kainate-mediated excitatory neurotransmission, respectively. The multiple mechanisms of action associated with FBM, TPM, ZNS, GBP, and perhaps LTG, and the unique modulation of GABA levels by VGB and TGB, are likely to account for the anticonvulsant efficacy of these newer AEDs in patients with epilepsy. For each of the new drugs, their proposed mechanisms of action are discussed in relationship to their preclinical and clinical anticonvulsant profiles.
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Status epilepticus (SE) treatment should proceed on four fronts: termination of SE, prevention of recurrence, management of potential precipitating causes, and management of SE complications and underlying conditions. The intensity of the treatment should reflect the risk to the patient from SE, and drugs likely to depress respiration and blood pressure should initially be avoided. The Veterans Administration cooperative trial showed that when treating overt SE, first-line treatment success rates were: lorazepam 64.9%; phenobarbital 58.2%; diazepam/phenytoin 55.8%; and phenytoin alone 43.6%. ⋯ Patients at this stage should undergo continuous electroencephalogram monitoring. Once SE is controlled, prevention of seizure recurrence should be individualized to each patient. The major complications of generalized convulsive SE (GCSE), rhabdomyolysis and hyperthermia, should be watched for and treated.