Reckitt Benckiser, the UK household goods maker, on Monday agreed to buy Adams Respiratory Therapeutics, a small US pharmaceutical group, for $2.3bn as it outlined plans to build a global empire in over-the-counter drugs.

Adams, which owns cough and congestion drugs Mucinex and Delsym, gives Reckitt a foothold in the US. It now plans to expand sales of the two drugs in overseas markets.