UPDATE 1-Schering plans anesthesia drug study after setback

(Adds details on drug, share price)

NEW YORK, Dec 3 (Reuters) - Schering-Plough Corp SGP.N plans to conduct a clinical study for its anesthesia-reversal drug sugammadex next year to test for allergic reactions, four months after U.S. regulators declined to approve the potential blockbuster product.

The drugmaker is developing the study to address issues raised by the U.S. Food and Drug Administration about the medicine, also known as Bridion, the company said in a posting on its Website late on Tuesday.

The study design is still being developed, although it will involve healthy volunteers and include repeat exposure to the drug, which reverses the effects of anesthesia many times faster than standard current treatments.

Schering-Plough said in August that the FDA had issued a "not-approvable" letter for sugammadex, stunning investors who had expected the drug's approval after it earlier received a unanimous recommendation from an FDA advisory panel.

Just last week, Schering-Plough touted the drug as one of five "stars" of its research pipeline at a meeting with investors, saying it had potential to achieve annual global sales of $1 billion if approved in the United States.

European regulators approved Bridion in July, and the drug has been launched in seven European countries with additional launches planned, Schering-Plough said.

Because of the new study, Leerink Swann analyst Seamus Fernandez said Schering-Plough was now unlikely to file a new U.S. application for sugammadex before 2010.

Schering-Plough, which acquired the drug a year ago through its purchase of Organon Biosciences, has called the medicine a revolutionary advance and one of the jewels of its Organon deal.

Shares of Schering-Plough were down 2.5 percent to $15.72 in morning trading on the New York Stock Exchange, amid a 0.6 percent decline for the American Stock Exchange Pharmaceutical Index of large U.S. and European drugmakers.DRG.

(Reporting by Lewis Krauskopf and Ransdell Pierson, editing by Dave Zimmerman)