Walgreens slashed its 2019 forecast after falling short of expectations in what its CEO described as the most difficult quarter since the company was formed a few years ago.

The nation’s largest drugstore chain now expects adjusted earnings per share growth to be flat this year, compare to a previous forecast for growth of 7% to 12% that it had reaffirmed in late December.

The company also said Tuesday that its adjusted earnings per share slipped 5% to $1.64 in the second quarter.

FactSet says analysts were expecting earnings of $1.72 per share.

Walgreens Boots Alliance Inc., based in Deerfield, Illinois, runs more than 18,500 stores in 11 countries and, along with CVS Health Corp., is one of the two biggest chains in the U.S. drugstore market.