Germany's Bayer and British consumer products giant Reckitt are said to have emerged as frontrunners to win the auction for the Merck & Co consumer products unit, each reportedly offering roughly $13.5 billion.

As both bidders are very keen to buy the asset, the price tag could go higher in the final days, sources told the news agency Reuters.

The sale would be the latest in a wave of recent healthcare deals. The surge has driven healthcare M&A volumes to $153.3 billion so far this year, with pharmaceuticals transactions accounting for 71%.

The Merck auction also is believed to have drawn interest from several other healthcare and consumer giants including Procter & Gamble Co, Boehringer Ingelheim, Novartis and Sanofi.

Reckitt owns over-the-counter (OTC) medicines including Mucinex and Nurofen and the international rights for the Scholl foot care business. Its chief executive told Reuters in September that the company aimed to be a major player in consumer healthcare and had the firepower to do sizeable deals. Bayer already has a strong portfolio of consumer products including pain medication Aleve and antacid Alka-Seltzer, which it picked up at the beginning of 2005 with the acquisition of the over-the-counter consumer health business of Swiss drugs giant Roche, but is looking at deals to expand the business further.

In 2012, Bayer lost a bidding war with Reckitt for Schiff Nutrition International Inc, which agreed to sell to the British consumer products group for $1.3 billion.

Merck wants to sell its consumer unit as it is not a leader in this market, with a share of only around 1%.

The US drugmaker is following in the footsteps of other drugmakers such as Pfizer, which sold its infant-nutrition business to Nestle for $11.9 billion in 2012 and last year spun off its animal health unit as a separate publicly traded company called Zoetis.