Federal health regulators have issued a warning letter to Baxter International Inc. for exaggerating the benefits of its lung drug in brochures to physicians.

The Food and Drug Administration letter cites the Deerfield, Ill.-based company for making "misleading efficacy claims" in promotional materials for its drug Aralast.

The drug is a synthetic form a human protein that prevents the breakdown of lung tissue. Doctors prescribe the drug to patients who lack the protein and are at increased risk of emphysema.

But the FDA says Baxter's brochure overstates the drug's ability to prevent such lung ailments, suggesting that it offers a "protective threshold" when given at certain dosing levels. According to agency regulators, the protective effect claimed by the company has not been established in clinical trials.

The FDA's letter, dated Aug. 3, notes that the drug and device maker has been warned for similar violations twice in the past two years.

"We are very concerned by your continued violative promotion of your products," states the letter, signed by the head of compliance for FDA's biologic drug division.

A Baxter spokesman said Tuesday the company has halted use of the brochure and responded to the agency Aug. 10.

Baxter makes a broad mix of medical staples used in hospitals - including blood plasma, kidney dialysis treatments and cancer drugs.

The FDA regularly issues warning letters to companies that do not follow regulations for manufacturing, marketing and testing. The letters are not legally binding, but the agency can take companies to court if they are ignored.