GlaxoSmithKline (NYSE: GSK) and drug partner Valeant Pharmaceuticals (NYSE: VRX) have received U.S. Food and Drug Administration approval on a new epilepsy drug, but it must be classified as a controlled substance, and regulators are also requiring a formal strategy to inform doctors and patients about the drug's risks.

Ezogabine, which will be marketed in the United States as Potiga, is an add-on treatment for partial-onset seizures in adults. Potiga is already approved in Europe where the drug is known as retigabine and sold under the brand name Trobalt.

"We believe this product will play a needed role in the management of partial-onset seizures in appropriate patients who are uncontrolled on their current medications," Susan Hall, head of research and development at Valeant, said in a prepared statement.

U.S. approval followed some additional work that the companies needed to do following concerns raised last year. While an advisory committee recommended approval after finding that the compound was safe and effective, concerns were also raised about some patients' inability to urinate while using the drug. The committee said such concerns could be mitigated by patient monitoring.

The FDA is requiring a more formal Risk Evaluation and Mitigation Strategy, or REMS. These formal plans are reserved for riskier drugs and typically outline how a company will manage risks and inform doctors and patients about them. FDA's approval of Potiga also came with a recommendation that the drug be scheduled as a controlled substance. Final classification of the drug will be done by the Drug Enforcement Administration and Potiga will not be commercially available until then. But GSK and Valeant say they expect the drug to be commercially available in U.S. pharmacies by the end of 2011.

Epilepsy affects about 50 million people around the world, according to the World Health Organization. A minimum of 250 million people experience at least one seizure in their lifetime, and at least 2.4 million new cases of epilepsy occur each year.

London-based GSK, which has its U.S. headquarters in Research Triangle Park, North Carolina, entered into an agreement with Valeant in 2008 that paid the Canada-based company $125 million up front to license and collaborate on the epilepsy drug candidate. Valeant is eligible for up to $545 million in milestone payments. The company could receive an additional $150 million for progress on backup compounds to the drug.

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