SAN FRANCISCO -- San Francisco's ban on cigarette sales by pharmacies such as Walgreens and Rite Aid will go forward Wednesday, a Superior Court judge has ruled.

The ordinance, enacted by the Board of Supervisors last month, bans tobacco sales by pharmacies, which are defined as retail stores containing a licensed pharmacy, but exempts grocery stores and so-called "big box" stores such as Safeway and Costco that contain pharmacies.

Walgreens Co., which operates more than 50 stores in San Francisco, had asked for a preliminary injunction halting the ban, arguing it unfairly favors the larger stores.

Attorneys for Walgreens claimed the first-of-its-kind prohibition violated equal protection laws and would cause irreparable harm to the company.

But Judge Peter Busch ruled the city had a rational basis for enacting the ban and denied the Walgreens motion.

City attorneys had contended that the public trusts pharmacies as health-promoting businesses and that the sale of tobacco by drugstores "sends an implicit message that smoking is acceptable."

Extending the ban in the future to big-box stores is under consideration, they said.

Attorneys for Walgreens, who said the company stands to lose millions of dollars because of the ban, promised to appeal today's ruling.

The ban has also been challenged in federal court by the Richmond, Va.-based tobacco company Philip Morris on grounds it violates the company's First Amendment right to free speech, by ending cigarette advertising and displays in stores.