Drugmaker Sanofi-Aventis has agreed to buy U.S. consumer healthcare group Chattem Inc for around $1.9 billion, in a deal which will give Sanofi over-the-counter presence in the United States.

Sanofi said it would start a tender offer for all of Chattem's shares at $93.50 per share in cash. The French group said the offer represented a 34 percent premium above the Chattem's closing share price on December 18.

Sanofi added that the transaction was valued at around $1.9 billion and had been backed by Chattem's directors. It also said the acquisition was expected to be accretive to Sanofi's earnings as early as year one.

The acquisition of Chattem will be a significant milestone in Sanofi-Aventis' transformation strategy and will provide us with the ideal platform in the U.S. consumer healthcare market, which represents 25 percent of the current worldwide opportunity, Sanofi Chief Executive Christopher Viehbacher said in a statement.

He told a conference call that Chattem was an ideal entry into the U.S. and would manage its Allegra drug, which is losing its status as a prescription drug.

Also on Monday, Sanofi said it had stopped developing two medicines as part of an overhaul of its research and development portfolio, saying they would not bring significant benefits.

Chattem, which was founded more than 100 years ago, makes and sells household and personal care products such as over-the-counter drugs, cosmetics and dietary supplements.

Its brands include Gold Bond, Icy Hot, Cortizone-10 and Unisom.

In October, Chattem made a third quarter net profit of $23.4 million and the company also maintained its 2009 financial guidance.

Sanofi shares were down 0.9 percent at 54.22 euros in early afternoon trade.

(Reporting by Sudip Kar-Gupta, Editing by Marcel Michelson and Rupert Winchester)