Walgreen Co. (WAG) said same-store sales rose 3.5% in March from a year earlier, as higher pharmacy sales offset weaker front-end results.

Drugstore retailers' sales have been pressured by a wave of major generic-drug introductions. The shift in consumers' drug purchases toward generics has led pharmacy companies to take steps to improve their performance--including a partnership by Walgreen and European drug giant Alliance Boots with drug wholesaler AmerisourceBergen Corp.

In the pharmacy section, same-store sales rose 8%. Same-store prescriptions filled improved 5.1%. Pharmacy sales accounted for 65% of total sales for the month.

During March, same-store sales shrank 3.4% in the front-end of the store. Same-store customer traffic decreased 4% while basket size increased 0.6%.

Total drugstore sales increased 4.5% to $6.43 billion.