The offer has the support of both the company's supervisory and management boards and of institutional investors holding 20.2% of the Mediq's shares. It values the company's stock at €775 million, or €13.20 per share -- a premium of 53% over the closing price on Friday.

The deal follows more than a year of internal discussions within Mediq over the best way to finance expansion, but was not the result of an auction, according to Mediq spokesman Ynte Hoekstra. He said the company made six acquisitions in 2011 and needed to raise finance either on the market or from new investors.

"As of mid-2011, we were discussing ways forward -- whether to stay listed, seek a strategic partner or turn to private equity; and there were other options, I presume," Hoekstra said. "During the process, Advent came up with an indicative offer. That was in June."

Hoekstra said the company had made it clear to Advent it did not want to be broken up or make changes to its governance. Instead it wanted support to expand its devices and pharmaceuticals distribution business in the Netherlands and internationally and its 226-strong pharmacy chain within the Netherlands. Mediq has net debt of about €258 million.

Based in Utrecht, Netherlands, Amsterdam-listed Mediq also has a chain of pharmacies in Poland. Its distribution business operates in 15 countries. The company has over 8,000 staff in Europe and the U.S. and generated 2011 sales of €2.66 billion.

As of midafternoon in Amsterdam, Mediq was trading at €12.88, up 48% on the Friday close.

Advent said it had irrevocable undertakings to accept the offer from Templeton Investment Counsel and Silchester International Investors, which between them own over 20% of the company's stock. It also said it had full financing in place for the offer.

Advent did not name the lenders. It took financial advice from Deutsche Bank AG, Rabobank NV and BNP Paribas SA. Freshfields Bruckhaus Deringer LLP provided legal advice to the buyer.

Mediq was advised by ING Asset Management NV and Allen & Co. LLC.