NEW YORK (Reuters) - Abbott Laboratories (>> Abbott Laboratories) is considering selling a big chunk of its mature drugs, joining a list of large drugmakers seeking to sell their older products in an effort to focus on high-growth areas, people familiar with the matter said.

Abbott's portfolio of mature drugs being reviewed for sale has around $2 billion (1.18 billion pounds) in annual revenue and could fetch more than $5 billion, the people said.

The U.S. drugmaker is working with Morgan Stanley (>> Morgan Stanley) to find a buyer for the off-patent, or established products, the people added, asking not to be identified because the matter is confidential. Representatives for Abbott and Morgan Stanley declined to comment.

Abbott has a big lineup of established pharmaceuticals, whose sales fell 3 percent last year to $4.97 billion. Analysts have been grumbling for the past year about the performance of the business, which has dragged down overall company results.

But Abbott Chief Executive Miles White previously expressed faith in the business, and appreciation for the cash flow it provides that can be used to fund research and other company operations.

Abbott's divestiture plans for part of its established products come at a time when its larger competitors are also looking to sell their own line-up of legacy drugs.

U.S. drugmaker Merck & Co (>> Merck & Co., Inc.) is considering selling a big portfolio of mature drugs that could fetch more than $15 billion, Reuters reported on Wednesday.

French pharmaceutical company Sanofi SA (>> SANOFI) has also been talking to buyers about selling $7 billion to $8 billion worth of mature products in the past few months, people familiar with the matter told Reuters earlier this week.

Those drug portfolios would provide good acquisition opportunities for generic drugmakers and specialty pharmaceutical companies, including Valeant Pharmaceuticals International Inc (>> Valeant Pharmaceuticals Intl Inc), Actavis Plc (>> Actavis PLC) and Mylan Inc (>> Mylan Inc), people familiar with the matter and analysts said.

Faced with healthcare spending cuts and generic competition, the pharmaceutical industry is undergoing a major restructuring, with companies playing to their strengths by building up certain businesses and divesting others.

Pfizer Inc (>> Pfizer Inc.), which spun off its animal health and infant formula businesses in recent years, is also considering whether to divest the hundreds of off-patent drugs that are mostly sold in emerging markets. But Pfizer has said it would be unable to do so until 2017, after the company has better examined the unit's financial performance.

Merck's plan to sell its established products is "highly consistent" with the company's refocusing strategy and could allow for more meaningful earnings growth, JPMorgan analyst Chris Schott said in a research note on Thursday.

(Additional reporting by Ransdell Pierson in New York; editing by Matthew Lewis)

By Soyoung Kim and Olivia Oran