GlaxoSmithKline and Valeant Pharmaceuticals International are celebrating this morning after regulators in the USA gave the green light to their epilepsy tablet Potiga.

The US Food and Drug Administration has approved Potiga (ezogabine), a potassium channel opener, as adjunctive treatment of partial-onset seizures in adults. The drug got the thumbs-up in Europe at the end of March, where it is marketed under the brand name Trobalt (retigabine).

However, the FDA has recommended that Potiga be classed as a controlled substance and final classification is still under review by the Federal Drug Enforcement Administration. The treatment will not be available until this process is complete, GSK expects a launch by the end of the year.

Furthermore, the FDA has insisted on a risk evaluation and mitigation strategy (REMS) for ezogabine, especially with regards to the risk of urinary retention. The problem was reported as an adverse event in 29 out of 1,365 patients involved in the clinical trial programme.

Despite this, the partners are happy to get the go-ahead, and Valeant R&D head Susan Hall said the US approval is an important milestone. "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," she added.

The approval is also good news for Sweden's Meda which licensed ezogabine to Valeant. The FDA green light triggers a milestone payment to Meda of $6 million and the firm is also entitled to receive royalties in the USA of 7% on net sales, plus other fees related to future development of the product.