March 26 (Reuters) - The U.S. FDA on Tuesday approved Merck's treatment for adults with high blood pressure due to constriction of lung arteries, adding another potential blockbuster drug to the pharmaceutical giant's portfolio.

(Reporting by Leroy Leo, Christy Santhosh and Mariam Sunny in Bengaluru and Michael Erman in New Jersey; Editing by Shinjini Ganguli)