Shares in Walgreens have fallen 10% since the merger with Alliance Boots was revealed on Tuesday.

Walgreens’ share price fell 4% in early trade yesterday, the Financial Times reported, demonstrating concerns over the deal, under which Walgreens could buy all of Alliance Boots for £10bn in three years.

Healthcare analyst at Gamco Investors Jeff Jonas said the reason for the fall in Walgreens’ share price erflects a market focus on the deal’s short-term implications, such as Walgreens cancelling its share buyback programme to fund the acquisition.

Jonas added: “There is a little bit of criticism over the deal, whether it’s the multiple that has been paid or going into a somewhat international deal.”

Some investors are also believed to be concerned over the amount of debt Walgreens would be shuoldering in the second phase of the transaction, when it would acquire all of Alliance Boots.

Online will also be a key focus for the new Walgreens-Alliance Boots partnership, according to a source. Both companies will work together to share best practice in online retailing, increasing the range of products sold through their websites.

It has also emerged that Boots held discussions with online grocer Ocado about selling its health and beauty own brands through the etailer, according to people familiar with the situation.

However, it is thought the two retailers are unlikely to come to an agreement.

The conversations underline Ocado’s ambition to grow its non-food division.