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Doctors who ate a single meal on a drug company's tab had a higher likelihood of writing a prescription for the name-brand drug that was being promoted instead of equivalent drugs that were cheaper, according to a new study. And the more meals — or the more expensive the meals — the greater the rate of prescribing the pitched drug.

The study, published in JAMA Internal Medicine, can't show that dinner or doughnuts with the pharmaceutical company caused physicians to preferentially prescribe a particular drug, but it revealed a striking correlation between breaking bread with a sales representative who is pushing a particular drug and doctors who are prescribing it. Overall, the meals received were modest, with an average cost of less than $20.

Jerry Avorn, a professor of medicine at Harvard Medical School who was not involved in the research, said the study was an improvement over past research because it narrowly examined doctors who received meals promoting a specific drug and their prescription behavior. The research could not prove a causal relationship, but Avorn thinks that meals are having an effect.

"The consequences are this is distorting health-care spending in a way that is large and unnecessary," Avorn said. "There has been a backing away from the really extravagant and frankly embarrassing giveaways of huge gifts of value. ... That’s good, but what a lot of people fail to see is having doctors learn about what drugs to use by virtue of free meals in nice restaurants is still problematic."

To do the study, the researchers at the University of California at San Francisco examined the prescribing practices of nearly 280,000 doctors for Medicare patients. They used a federal database that includes meals, travel, speaking fees and other financial relationships between doctors and drug companies and looked narrowly at doctors who received free meals promoting one of four drugs. They intentionally chose commonly prescribed drugs for which there was a brand name being promoted, competing with cheaper therapeutic equivalents.

For example, one of the promoted drugs was a brand-name statin, Crestor, used to lower cholesterol. Another treatment, Lipitor, has been shown to work as well as Crestor, and a cheap generic was available for Lipitor. Doctors who received a meal focused on Crestor four or more times prescribed it 1.8 times as frequently as doctors who received no meals. For a high-blood-pressure drug called Bystolic, those who received a single meal prescribed it at twice the rate of those who received no meals.

AstraZeneca, which makes Crestor, said in a statement that the company is committed to transparency and that it reports its payments to physicians.

"AstraZeneca does not offer anything of value to healthcare providers in exchange for prescribing AstraZeneca medicines," the statement said.

Rachel Hooper, a spokeswoman for Pfizer, which makes Lipitor and a drug included in the study that showed the same pattern, called Pristiq, echoed that point.

"While we have not had an opportunity to fully review the study, it is important to note that physicians, teaching hospitals and biopharmaceutical companies work together on research and share up-to-date information about our medicines for the benefit of patients," Hooper wrote in an email.

The study could not show that the meals caused the increased prescribing. Doctors who are more likely to prescribe a particular brand-name drug might simply be more likely to attend a dinner with the drug company that makes it. Some medical centers have introduced policies limiting or prohibiting the interactions, and payments are now reported publicly under federal law.

“This study cherry-picks physician-prescribing data for a subset of medicines to advance a false narrative," Holly Campbell, a spokeswoman for the industry trade group, PhRMA, wrote in an email. "Manufacturers routinely engage with physicians to share drug safety and efficacy information, new indications for approved medicines and potential side effects of medicines. As the study says, the exchange of this critical information could impact physicians’ prescribing decisions in an effort to improve patient care."

But R. Adams Dudley, a professor of medicine and health policy at the University of California at San Francisco who oversaw the study, argues that what meals buy is a doctor's time and a willingness to listen, which can be tremendously valuable.

"If you went in there with cash, and you said to the doctor, 'I’ll give you $7 to prescribe more Crestor,' they would be offended and wouldn’t talk to you," Dudley said. "But if you go in there with some doughnuts and the nurse says to the doctor, 'There are crullers in the conference room,' the doctor goes in there of their own free will. Humans, when they receive gifts, feel some urge to reciprocity. They’re willing to then listen to you."

An accompanying editor's note said that the correlations between company payments and prescription patterns have been shown many times and questioned whether a causal link even needs to be shown. There are legitimate reasons for doctors to work with drug companies, such as research and product development, the editorial argues. But gifts can raise uneasy questions.

"There are inherent tensions between the profits of health-care companies, the independence of physicians and the integrity of our work, and the affordability of medical care," JAMA Internal Medicine editor-at-large Robert Steinbrook wrote. "If drug and device manufacturers were to stop sending money to physicians for promotional speaking, meals, and other activities without clear medical justifications and invest more in independent bona fide research on safety, effectiveness, and affordability, our patients and the health care system would be better off."

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