Physicians with access to free drug samples are more likely to write prescriptions for costlier drugs than doctors who do not have access to free samples, a US study reports.

The average retail cost of prescriptions written by dermatologists with access to free samples was about twice the cost of those written by doctors at an academic medical centre where samples are prohibited, says the study, published in the current issue of JAMA Dermatology.

Researchers at the Stanford University School of Medicine found that branded drugs and branded generics accounted for 79% of prescriptions written by dermatologists across the US but only 17% of those written by physicians at the academic medical centre which prohibits samples.

The impetus for their study was a policy instituted in 2006 at Stanford Medicine, prohibiting its physicians from accepting samples or other industry gifts. After the change, the study’s lead author, Dr Alfred Lane, said he noticed a discrepancy between the medications he tended to prescribe and those prescribed by other doctors in the community.

“I realised that patients were referred to Stanford with prescriptions for newly-introduced branded drugs that were unfamiliar to me – sometimes I had to look up what they actually were,” said Dr Lane, emeritus professor of dermatology and pediatrics at Stanford.  “It wasn’t clear to me that there was much benefit to these drugs, and they were definitely very expensive,” he added.

By some estimates, drugmakers give free samples worth about $16 billion to US physicians each year. Many doctors feel this is a cost-effective way to help poorer patients who may not have insurance, or to allow patients to choose a preferred medication to which they are mostly likely to adhere.

However, national data does not support this view – poorer people and the uninsured are not the patients who are typically getting samples, said the study’s first author, Michael Hurley.

Opponents of drug samples argue that doctors may not take as much care describing sample medications and their effects as they would for non-sample medications, and that the samples serve as a form of marketing to both doctors and patients to influence treatment decisions.

The study, which focused on medications prescribed to treat adult acne, found that the average cost of prescriptions for a patient treated by a doctor who received samples was around $465, compared to about $200 for patients treated by a doctor without access to samples.

Also, only one of the top 10 medications prescribed at the academic medical centre which prohibits samples was also in the top 10 nationwide. In fact, nine of the 10 most-commonly prescribed medications nationwide were branded drugs or branded generics, and only 21% of prescriptions written by doctors nationwide were for generics, compared to 83% of prescriptions at the academic medical centre.

And 33%-92% of the time, nine of the top 10 nationally-prescribed drugs were supplied with prescriptions, although much cheaper generic versions existed for eight of these nine drugs.

"The negative consequences of free drug samples affect clinical practice on a national level, and policies should be in place to properly mitigate their inappropriate influence on prescribing patterns,” say the authors.