GSK kicks off over-the-counter drugs sale -sources

* Information memorandum due in next 1-2 weeks

* Private equity and trade buyers eye assets

* Auction may raise around $2.5 billion

* Brands for sale include painkillers, diet pill

By Ben Hirschler and Simon Meads

LONDON, July 1 (Reuters) - GlaxoSmithKline is pushing ahead with the sale of a clutch of non-prescription products, which may fetch around $2.5 billion, and will send out details to bidders shortly, people familiar with the matter said.

Following initial expressions of interest from a wide range of potential buyers, an information memorandum on the assets is due to go out either next week or the week after, the sources said on Friday.

Prospective bidders will then have about four weeks to put in non-binding offers.

Britain's biggest drugmaker said in February it planned to sell several non-core over-the-counter (OTC) products with combined sales of around 500 million pounds ($800 million), representing about 10 percent of its total consumer healthcare business.

Industry analysts have estimated the assets -- which include painkillers, vitamin supplements and the diet pill Alli, all sold primarily in Europe and the United States -- might fetch between 1.5 billion and 2 billion pounds.

A number of rival producers of OTC remedies have expressed interest. The auction, being run by Goldman Sachs, has also attracted a strong showing from private equity houses, the sources said.

Consumer healthcare is a favoured investment sector for private equity players, who have an appetite for carve-outs from Big Pharma and like the defensive nature of a business that has stable cash flows.

The world's largest buyout firms, including Blackstone , KKR , Apax and CVC , all have an interest in healthcare.

Non-prescription medicines are also a major focus for a number of GSK's rivals, including Sanofi , Novartis and Johnson & Johnson , some of whom may want to pick up assets now on the block.

Certain product lines could also appeal to smaller players such as Sweden's Meda (MEDAa.ST), which acquired other OTC medicines from GSK in a deal last December.

Despite the divestment, consumer healthcare will still remain a priority area for GSK. The company aims to focus its portfolio on top brands in Western markets and concentrate heavily on fast-growing opportunities in emerging markets.

GSK Chief Executive Andrew Witty said last month that there had been strong interest from both industry rivals and private equity houses in the consumer brands being offered for sale, adding that the sale process was likely to pick up over the summer months.

The company has promised to return cash from the sale to shareholders, though it has yet to decide on the best mechanism for doing this.

GSK restarted a share buyback programme earlier this year, and the disposal could underpin share repurchases in 2012, assuming the sale is completed towards the end of the year. ($1 = 0.626 British Pounds) (Additional reporting by Sven Nordenstam in Stockholm; Editing by Will Waterman)