UK-based cleaning products manufacturer Reckitt Benckiser announced Monday that it has agreed to buy US OTC drug maker Adams Respiratory Therapeutics for $2.3 billion.

Adams is a NASDAQ-listed specialty pharmaceutical group headquartered in Chester, NJ and markets two OTC cough treatments, Mucinex and Delsym, in the US.

Mucinex is currently the No.1 selling OTC expectorant in the US, Adams said.

Adams sales have grown to $332 million in the year to June 2007 compared with $14 million just four years earlier.

Commenting on the acquisition, Bart Becht, CEO of Reckitt Benckiser said in a statement: “Adams will add to our portfolio a new, rapidly growing powerbrand in Mucinex, a market and innovation leader in cough and congestion relief in the USA. Equally important, it will provide Reckitt Benckiser an entry into health care in the USA, the world’s largest OTC market.”