By that point, patients are often loath to change to generics, especially if they perceive that the brand-name drug is working.
What's more, the brand-name drug typically means higher costs from the outset for the insurer - costs that are then passed along as higher premiums to all those who are insured, authors Joseph S. Ross and Aaron S. Kesselheim wrote.
An industry group official countered that without coupons, patients may be less likely to take medicines.
"Today's high levels of cost sharing can pose a significant access barrier for patients, resulting in low adherence and poor health outcomes," said Matthew Bennett, senior vice president of the Pharmaceutical Research and Manufacturers of America.
Ross and Kesselheim reviewed 374 coupons for brand-name prescription drugs taken from a popular drug-coupon website. They were able to find lower-cost generic alternatives for 62 percent of the drugs - 231 out of 374.
Besides being readily available on the Internet, such coupons are sometimes distributed in doctor's offices, the authors wrote. Ross is an assistant professor at the Yale School of Medicine. Kesselheim, a Harvard researcher, earned degrees in law and medicine at the University of Pennsylvania.
Drug companies also can achieve brand loyalty by distributing free samples, but that is less effective because the patients who receive them do not need prescriptions, Ross said. Coupons, on the other hand, have sticking power.
"When they go back for a refill, the coupon may not still be there, but the prescription is already established," Ross said.
Bill Trombetta, a professor of health care and pharmaceutical marketing at St. Joseph's University, said patients do not always stick with a brand-name drug, as co-pays can exceed $80 once the coupon expires.
Some critics allege that coupons are illegal, amounting to a kickback. Several union health plans have sued manufacturers, so far without success.
Either way, Ross said, the practice seems to work, for a simple reason:
"People just don't like to switch medicines."
Contact Tom Avril at 215-854-2430 or firstname.lastname@example.org.