A free Viagra prescription or a no-cost trial of sleeping pills are examples of growing offers to U.S. consumers, but regulators and critics worry about the side effects of pitching medicines like selling soap.

Drug makers say the coupons, rebates and similar promotions lower patient costs or provide the chance to try new medicines. Consumer groups, however, say they may draw people to risky drugs they may not need, without long-term savings.

Coupons “can increase the patient’s desire to take a drug that may or may not be the most suitable drug ... This is not shampoo,” said Susan Sherry, deputy director of Community Catalyst, a Massachusetts-based group that has joined 22 others seeking a Food and Drug Administration ban on the giveaways.

The offers are appearing across the prescription drug business, trying to grab customers’ attention in magazines and on Web sites. Pfizer Inc., for example, offers a free prescription of impotence drug Viagra for every six filled. Patients can try seven days of the Sanofi-Aventis sleeping pill Ambien at no cost.

The FDA has raised concerns. In a notice earlier this year, the agency said “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.”

But that notice, which proposed a study of responses to mock insomnia drug promotions, was withdrawn, FDA spokeswoman Julie Zawisza said. Officials now are working to “identify the important issues or questions to be considered and to determine the appropriate role of the FDA,” she said.

More than 10 million patients since 1994 have redeemed free trial vouchers through programs run for various companies by drug wholesaler McKesson Corp., said Kerr Holbrook, vice president of marketing and business development.

The vouchers help cash-strapped patients who might otherwise delay therapy or skip a refill, Holbrook said. Unlike the free samples doctors often give out, obtaining drugs through a voucher is tracked by a doctor and pharmacist.

The program “ensures safety, and it ensures access to the patient at a good price,” he said.

Pfizer said its Viagra “value card,” which offers a free seventh prescription, is aimed at helping men afford the drug if they do not have insurance coverage for it.

“We’ve seen that for men with (erectile dysfunction) who are considering therapy for the first time, this program offers a reason to visit the doctor to discuss whether treatment is right for them,” Pfizer spokeswoman Alison Lehanski said.

Sanofi-Aventis spokeswoman Melissa Feltmann said the Ambien offer was meant to provide access to the sleeping drug and stressed patients must have a valid prescription.

Critics say a coupon could steer a person to a brand-name drug when a cheaper generic copy would work as well.

“All that does is get them used to being on the expensive drug,” said Dr. Jerry Avorn, a Harvard professor and author of the book “Powerful Medicines: The Benefits, Risks and Costs of Prescription Drugs.”

Some critics object to coupons attached to “reminder ads” that list only a drug name and no details about what it treats or possible side effects.

Diana Zuckerman, president of the National Research Center for Women & Families, said those offers are “particularly disturbing - to have nothing but ‘here’s some free sleeping pills’ with absolutely no information about why you might or might not want to take it.”

She added that “with any sleeping pill, you would want to be a bit more cautious” because of possible addiction or other side effects.

Freebies for children also are troubling, Zuckerman and others said.

Galderma Pharma, a joint venture of Nestle SA and L’Oreal, drew fire for giving free music downloads to patients who got prescriptions for acne drug Differin. That offer, seen as a bid to attract teenagers, has been stopped.

The Pharmaceutical Research and Manufacturers of America, an industry group, said abuses were rare and urged regulators to study coupon offers case-by-case rather than limiting them.

Harvard’s Avorn said the coupon trend was “the same symptom we have seen in the drug industry for years - the ascendancy of marketing over science” as companies fight for market share.

“They are getting so preoccupied with marketing, and unfortunately they seem to be less successful in coming up with creative drug solutions,” he said.