All of the drug chains face challenges on the regulatory, reimbursement and new drug introduction front. But Rite-Aid also faces the additional challenge of integrating Eckerd Stores, if shareholders approve the deal later this month. Rite Aid's new stores and relocations might not live up to expectations, and rising interest rates could affect its cost structure. Longs, with its larger format and greater reliance on general merchandise, faces pressure from discount stores.

Dollar General expected to post a 4.5% comp gain, with Dollar Tree to see a 3.0% gain, Fred's a 1.8% rise, and Family Dollar a 1.0% rise.

Ironically, though, dollar stores face some of the same competitive pressures as drug retailers, including competitive pressures from discounters, as the traditional mass merchant chains negotiate better deals with suppliers. Fred's, which also sells prescription drugs, also could be hurt by declining reimbursement for Medicaid recipients.

But they face different pressures, as well, including the possibility of a less favorable exchange rate with China (where many good are manufactured), rising real estate costs and potential market saturation.

"Over the past few years, the retail environment has become increasingly competitive, with other retailers offering 'hot' promotions to drive traffic during the holiday period," said Adler in the report on dollar stores. "Furthermore, we continue to believe that the low-end consumer is financially stretched."