(Bloomberg) — Doctors who accept free meals from the pharmaceutical industry are more likely to prescribe certain branded drugs to Medicare patients than generics, according to a study published Monday.

The article in JAMA Internal Medicine documents a group of almost 280,000 doctors who received industry-sponsored meals, typically costing less than $20, in 2013. The study found that the doctors more frequently prescribed the four most common brand-name drugs that were available in the Medicare Part D program. In the case of Bystolic, a beta blocker for high blood pressure, physicians who received at least four meals chose the brand 5.4 times as often as generics.

“What was most surprising to me was that such small payments were associated with big differences in physician prescriptions,” said Colette Dejong, one of the study’s authors and a research fellow at the Center for Healthcare Value at the University of California at San Francisco. “It was previously thought it takes a certain amount of money to influence a doctor, and the current guidelines are written that way.”

Drugmakers and doctors have long shared a close relationship that recently has become more documented. Last year, government data showed that U.S. doctors and teaching hospitals received $6.49 billion from drug and medical-device makers in 2014. While the industry has said that covering the costs of meals helps enable communication with doctors, critics contend that physicians potentially expose themselves to undue influence.

More Meals, More Prescriptions

Brand-name drugs were prescribed more often even when doctors received just one meal, and prescription frequency grew with the number of meals and their costs, according to the study. Besides Bystolic, the authors looked at Crestor, a statin that treats high cholesterol; Benicar, an ACE inhibitor that treats high blood pressure; and Pristiq, which treats depression. Doctors who received four or more meals paid by the industry prescribed Crestor at 1.8 times the rate of those who received no free meals. The ratio was 4.5 times for Benicar and 3.4 times for Pristiq.

PhRMA, the Pharmaceutical Research and Manufacturers of America that serves as the industry’s trade association, said prescribing patterns are based on individual patients’ needs.

“This study cherry-picks physician prescribing data for a subset of medicines to advance a false narrative,” the group said in an e-mailed statement. “Manufacturers routinely engage with physicians to share drug safety and efficacy information, new indications for approved medicines and potential side effects of medicines.”

The American Medical Association’s ethics guidelines state that physicians cannot accept any gifts of more than minimal value or for which reciprocity is expected or implied. The main industry association for drugmakers also places limitations on how companies may purchase meals for doctors.

Arthur Caplan, who heads the ethics program of the Global Institute for Public Health at New York University, said even gifts with limited value such as meals can influence a recipient’s behavior in a subtle way.

“Any gifting creates a sense of obligation,” Caplan said. “Small gifts attach themselves as marketing reminders. You get a chance to give your message.” 

The group of doctors in the study received 63,524 industry-sponsored meals in the last five months of 2013. The study linked two national data sets, and the results are cross-sectional and reflect an association, not a cause-and-effect relationship, according to the authors.

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