WASHINGTON — In the battle for new patients and greater market share, U.S. drug makers are putting their faith in a time-tested, albeit pedestrian, marketing strategy.

Coupons, money-back guarantees, rebates and other supermarket-friendly promotions offering "10 percent off," "free trial offers" or "buy six prescriptions, get one free" are now standard marketing tools for many top-selling prescription drugs.

The heartburn drug Prevacid offers patients $25 rebates on their next prescriptions. Lipitor and Crestor, two leading cholesterol-lowering drugs, offer free 14- and 15-day trial periods. And Lotrel, a blood pressure medication, will reimburse consumers' out-of-pocket drug costs for up to four months if the drug doesn't work effectively.

Drug industry officials said the offers allow consumers to test and compare medications without bearing the full financial risk. By providing relief from high drug prices, they also can improve interaction between doctors and patients.

"In some cases it becomes a tool for them to initiate a potentially difficult conversation, (about topics) such as depression or erectile dysfunction. And that's important," said Paula Garrett, a consumer marketing specialist at Eli Lilly.

But as the promotions become more ubiquitous, turning up in magazines, on Web sites and in doctors' offices, they're also creating unease among some in the medical community, including in the U.S. Food and Drug Administration.

A group of 24 patient advocacy groups led by the Boston-based Prescription Access Litigation Project has asked the FDA to ban the promotions. The groups claim that the offers improperly influence a doctor's prescribing decisions and steer patients toward expensive brand-name medications and away from cheaper generic drugs.

"I think those are legitimate concerns," said Dr. Richard Kravitz, the director of the Center for Health Services Research at the University of California, Davis, Medical Center.

Promotions aimed at children have drawn particular concern. Differin, an acne drug, offers $10 prescription rebates and free music downloads to patients 13 and older.

Diane Zuckerman, president of the National Research Center for Women & Families, said in a letter to the FDA that the agency should immediately ban such promotions aimed at youth under age 18.

Even the FDA is concerned. In a recent agency filing, regulators said that "prescription drugs promoted with coupons or free trial offers may be seen as more widely indicated, more appropriate and/or less risky than they really are."

The problem is especially great when the offers are included in so-called "reminder ads," which provide no information about the advertised drug's potential risks.

Charles Brown, a vice president at NCH Marketing, a coupon processor in Deerfield, Ill., said discount promotions are popular because researchers have found that they spur more sales than by simply lowering a product's price.

"To bring an increase in sales, it really requires some type of promotion, merchandising or some event to bring that awareness and excitement about savings. That's where coupons come in," Brown said.

It's partly psychological, said Kent Monroe, a marketing professor emeritus at the University of Illinois who's studied consumers' responses to coupons.

"When people perceive that an item is on sale or on deal, that does enhance their perception of the value of the product itself," Monroe said.

That's OK for discretionary items such as food, clothing and household goods. But "for more complex products like prescription drugs, where supervision of a physician is required to evaluate both appropriateness and performance, coupons and free trial offers may send different signals," the FDA wrote recently. "These signals may foster consumer misperceptions about the advertised prescription drug product."

To sort it all out, the FDA will conduct a study on whether discounted promotions in drug print ads affect how consumers view the risks and benefits of an advertised drug.

Drug makers say no changes are necessary. Scott Lassman, the assistant general counsel for the Pharmaceutical Research and Manufacturers of America, said in a recent FDA filing that the promotions are regulated by various state and federal laws.