RONKONKOMA, N.Y — NBTY Inc. next month plans to hold a special meeting of shareholders to vote on its agreement to be acquired by private equity firm Carlyle Group.

The nutritional supplements manufacturer and marketer said Tuesday that it has scheduled a meeting of stockholders on Sept. 22 to consider and vote on the proposal to adopt the acquisition agreement announced July 15 for NBTY to be purchased by Alphabet Holding Co., an entity formed by an affiliate of The Carlyle Group. 

The $3.8 billion acquisition is one of the largest private equity deals thus far in 2010. NBTY announced the deal a day after reports emerged that the company was being pursued by both Carlyle and rival private equity firm Blackstone Group LP.

NBTY reported that it expects the deal to close by the end of the year. The company’s roster of supplement brands includes Nature’s Bounty, Osteo Bi-Flex, Sundown, MET-Rx, Ester-C and Pure Protein.