The Food and Drug Administration is cracking down on pharmacies that sell customized hormone mixtures as antidotes for menopause symptoms such as hot flashes, saying they are being promoted with false claims about their benefits and contain an ingredient the agency hadn't approved.

The regulator's move ramps up a contentious debate over growing use of the customized hormone products, which have surged in popularity since a government study in 2002 raised questions about the health risks associated with traditional menopause hormone drugs. They were also boosted by actress Suzanne Somers, who promoted use of them in her books.

Drug maker Wyeth, which sells hormone drugs for the same uses, had complained to the agency about pharmacies' practices. Wyeth reported $791 million in revenue from hormone products for the first nine months of 2007. In a sign of the issue's high profile, the FDA got more than 70,000 comments from patients, pharmacists and others about the company's petition, many defending the pharmacies. The controversy comes as millions of women born at the peak of the postwar baby boom are entering their 50s. The North American Menopause Society said an estimated 6,000 U.S. women reach menopause every day, or over two million a year.

In letters, the agency warned seven individual pharmacies to stop using certain promotional language, including the popular descriptive phrase "bio-identical." The FDA also told the pharmacies that they couldn't sell hormone mixtures containing the ingredient estriol, which the regulator views as a new drug that hasn't won agency approval. The special hormone combinations, known as "compounded" products, must be prescribed by a physician.

"We certainly hope other pharmacies will take heed," said Deborah M. Autor, director of the FDA drug center's office of compliance. The FDA said it wasn't attempting to ban the sales of all compounded hormone products. Agency officials also said they hadn't received reports of safety problems tied to the compounded mixtures, and that the warning letters weren't sent in response to Wyeth's petition.

Compounding pharmacies said the agency had gone beyond its authority in attacking the use of estriol. "We are greatly troubled, to put it lightly," said L.D. King, executive director of the International Academy of Compounding Pharmacists, a trade group. He said that the majority of his members' compounded hormone mixtures include estriol. Mr. King said the group will seek to meet with FDA officials. The FDA is already being sued by pharmacies that have sought to limit its authority over compounded products, and an appeal in that case is set to be heard today.

The increasing use of the compounded hormone products - once a niche business - has been driven by both health and business factors. Often, the custom mixtures are promoted as more natural and akin to the body's own hormones than commercially available drugs. A number of medical groups have questioned the compounded hormones' benefits. The North American Menopause Society and the American College of Obstetricians and Gynecologists have said there is no evidence that compounded hormones are better or safer than commercial drugs.

Phillip Pylant, owner of one of the seven pharmacies, Village Compounding Pharmacy in Houston, said his pharmacy goes by "the highest standards" and follows "all the rules we're supposed to follow." Elaine Blieden, a pharmacist at Panorama Compounding Pharmacy in Lake Balboa, Calif., said the pharmacy was taking the FDA's letter "very seriously." A lawyer representing the owners of Reed's Compounding Pharmacy, in Tucson, Ariz., said he couldn't comment on specifics.