UPDATE 1-U.S. FDA proposes restricting compounding of 3 drug substances

(New throughout, adds further details on the FDA's action, background on vasopressin)

Aug 27 (Reuters) - The U.S. Food and Drug Administration on Monday proposed excluding three substances from a list of ingredients that could be used to manufacture compounded medications in bulk for use by hospitals and doctors' offices.

The action was the first time the regulator has moved to exclude any substance from a list of ingredients that may be used to produce in bulk compounded medications that do not need to go through the agency's safety approval process.

Those substances included vasopressin, the active ingredient in Endo International Plc's blood pressure drug Vasostrict, which has been the subject of a lawsuit by the company targeting how the FDA regulates drug compounding.

The other two substances are bumetanide and nicardipine hydrochloride, which the regulator said are also ingredients of one or more FDA-approved drug products.

"Compounded drug products can serve an important medical need for patients, but they dont meet the same standards as FDA-approved drugs," FDA Commissioner Scott Gottlieb said in a statement.

Compounded medications are custom-made medications that traditionally were formulated by pharmacies for specific patients to address allergies or other individualized issues.

The FDA's announcement came after Athenex Inc, a Buffalo, New York-based pharmaceutical company, said on Aug. 13 that it had begun selling a compounded formulation of vasopressin that could compete with Vasostrict, Endo's top-selling drug.

Endo had no immediate comment. Athenex did not respond to a request for comment. (Reporting by Nate Raymond in Boston; Editing by David Gregorio)