Bayer has closed its $14.2 billion acquisition of US Merck & Co's $2.2 billion consumer care business after the transaction was approved by anti-trust authorities in all markets except Mexico and South Korea.

With the deal, the German group, which recently announced plans to carve out its engineering plastics business to concentrate on life sciences, said it has become the leading producer of over-the-counter drugs in the Americas and has achieved "top global positions" in key OTC categories, including dermatology and gastroenterology.

The integration of the Merck portfolio will make Bayer world's number two in non-prescription drugs, behind the combined business of Novartis and Glaxo SmithKline and ahead of the previous global leader Johnson & Johnson

Calling the purchase "a milestone," CEO Marijn Dekkers said Bayer intends to continue expanding its OTC activities both through organic growth and bolt-on acquisitions.

The combined Bayer-Merck business, which has pro forma sales of $7.4 billion million based on 2013 figures, is headed by Erica Mann, member of the Bayer HealthCare Executive Committee responsible for the Consumer Care Division.

Bayer said it expects the integration of the two companies' portfolios to generate synergies "in the neighbourhood of $200 million per year by 2017," especially as regards market spend and cost of goods. Revenue synergies of a further $400 million are expected from the increased commercial presence.

Executing the transaction is expected to cost around $500,000, and the group said it the acquisition is foreseen to yield a positive contribution of 2% to core earnings in the first year after closing.