Ezogabine has been approved as adjunctive therapy for partial onset seizures in adults but will not be available until later this year.
Ezogabine is the first neuronal potassium channel opener approved for treating epilepsy, according to a Food and Drug Administration statement issued on June 13 announcing the approval. "Although the mechanism of action is not firmly established, the drug may act as an anticonvulsant by reducing excitability through the stabilization of neuronal potassium channels in an ‘open’ position," the FDA statement said.
Ezogabine, which will be marketed as Potiga, was developed by Valeant Pharmaceuticals North America and will be distributed by GlaxoSmithKline.
A statement issued by GSK on June 13 said that the FDA has recommended that ezogabine be scheduled as a controlled substance and that final classification was under review by the Drug Enforcement Administration. The drug is expected to be available in U.S. pharmacies by the end of 2011, after this process is completed, according to GSK.
The most common adverse reactions associated with ezogabine in clinical trials included dizziness, fatigue, confusion, vertigo, tremor, problems with coordination, double vision, attention problems, memory impairment, and lack of strength, according to the FDA. Other possible adverse events include hallucinations, psychotic symptoms and other neuropsychiatric symptoms, which typically resolve within 7 days of stopping the drug, according to the FDA.
Urinary retention, which usually presents during the first 6 months of treatment, is another side effect associated with ezogabine, so urologic symptoms in treated patients should be carefully monitored, the FDA statement said.
The GSK statement said that the FDA has determined that a Risk Evaluation and Mitigation strategy to inform health care professionals about the risk of urinary retention is needed for the drug.
At a meeting in August 2010, an FDA advisory panel unanimously agreed that ezogabine had been shown to be effective as adjunctive therapy for partial onset seizures, but recommended that treated patients be closely monitored for the development of urinary retention. Members of the panel agreed that the risk of urinary retention could be mitigated by monitoring patients, pointing out the importance of educating clinicians in how to properly evaluate patients for changes in urinary symptoms.
Ezogabine was approved in the European Union in March 2011. Outside of the United States, it is known as retigabine and is marketed as Trobalt, according to GSK.