NEW YORK ( TheStreet) -- Walgreen's February same-store sales inched up 0.4%, slightly missing Wall Street's forecast. Analysts expected a 0.5% gain during the month. This is the third consecutive month Walgreen missed same-store sales expectations. By division, pharmacy comparable sales increased 0.9%, while front-end decreased 0.6%. The drugstore said its pharmacy same-store sales were negatively affected by 2.4% due to the introduction of generic drugs in the last 12 months and fewer flu cases. Walgreen's same-store sales were down 1.1% in January and 0.3% in December. Prior to that, the last time same-store sales had declined was in February 2009. Total sales rose 3.2% to $5.31 billion. Shares of Walgreen are slipping 0.6% to $32.50 in pre-market trading. -- Reported by Jeanine Poggi in New York. Follow TheStreet.com on Twitter and become a fan on Facebook.