In choosing which drugs to prescribe, doctors often select medications for patients despite a lack of conclusive medical evidence of their effects and safety, according to a new study led by a researcher at the Stanford University School of Medicine.

Of a wide sampling of prescriptions dispensed to patients in 2001, 21 percent were intended to treat medical conditions for which the drugs lacked specific approval from the U.S. Food and Drug Administration, though other published research suggested possible benefits. Furthermore, about three of every four of those prescriptions were for conditions for which there were little or no evidence of the drugs’ effectiveness.

This practice of “off-label prescribing” offers doctors flexibility and innovation in treating patients but also carries unknown risks. The findings, which will be published May 8 in the Archives of Internal Medicine, are believed to be the first estimate based on a sizeable data base of the actual number of off-label prescriptions among the 100 most-used drugs and 60 other randomly-selected, commonly used medications.

The results show scientific evidence plays only a partial role in a physician’s treatment decisions, said Randall Stafford, MD, PhD, associate professor of medicine at the Stanford Prevention Research Center and senior author of the study. Indeed, many doctors might be unaware if a drug has been FDA-approved for a specific use or how much research supports its use, he added.

“Many doctors prescribed a drug when there is little or no evidence supporting its efficacy and safety,” Stafford said. “The study can’t tell us why doctors prescribe drugs off label. Some uses are more reasonable than others, but, by definition, off-label uses receive less scrutiny than FDA-approved indications.”

It is unclear how off-label uses become established within the medical community in cases where limited or no scientific evidence backs up their use. Informal communication between physicians, promising or preliminary scientific studies, and marketing by the pharmaceutical industry could play roles, Stafford commented.

Of course, just because a drug is unapproved by the FDA doesn’t mean it’s ineffective. The FDA approves drugs for treating specific indications only, and there are many reasons why a drug might not have been approved for treating a particular condition, Stafford said. Undergoing the trials necessary for approval, for instance, can be time-consuming and expensive. If a drug’s patent has expired, a pharmaceutical company is unlikely to pursue approval for another indication.

What’s more, many drugs belong to classes of pharmaceuticals that work in similar ways, though each might have different side effects. It would be logical to assume that a drug in a particular class would have the same effect as others in that class. Other off-label use may represent an extension of labeled uses or evolving new uses that have not been evaluated stringently. Greater caution is advised in such circumstances, Stafford said.

“These off-label uses have not been scrutinized the way FDA-approved uses have been,” Stafford explained. “While this situation is more risky, some patients might have conditions where taking such risks might be warranted.”

For patients with severe medical conditions, the potential benefits of treatment might outweigh the increased risk associated with off-label use. A physician might choose to prescribe a drug off-label to adjust for a patient’s sensitivities, to avoid interactions with other drugs or to try a different approach if FDA-approved drugs haven’t worked. While nothing prevents a doctor’s prescribing a drug off-label, pharmaceutical companies are prohibited from directly promoting such uses.

With colleague and first author David C. Radley, MPH, of Dartmouth Medical School’s Center for Evaluative Clinical Sciences, and collaborator Stan N. Finkelstein, MD, of the Massachusetts Institute of Technology, Stafford compiled data taken from the 2001 National Disease Therapeutic Index, a continuing survey of U.S. physicians conducted by IMS Health, a pharmaceutical and health-care marketing company based in Plymouth Meeting, Pa. The survey compiles data from 3,500 physicians who report information about patient care during two randomly selected, consecutive workdays every quarter. The data represents 403,957 encounters between doctors and patients.

According to the IMS Health data, the 160 drugs selected for the study accounted for an estimated 725 million in annual prescriptions. About 575 million, or 79 percent of the total, were prescribed for a condition approved by the FDA. Off-label prescriptions accounted for 150 million, or 21 percent of the total number. Of those, 27 percent were for indications supported by scientific evidence, while the remaining 73 percent, or 109 million prescriptions, had little or no evidence.

The team considered a drug’s use scientifically supported if the indication appeared with an evidence rating of good or excellent in DRUGDEX, a nationally recognized pharmaceutical compendium. Rigorous observations in clinical settings and controlled trials must determine the drug’s efficacy before such a rating is assigned.

The medication gabapentin was prescribed off-label most frequently-about 83 percent of the total prescriptions for that drug. In 66 percent of these instances, the drug had little or no scientific evidence for its efficacy in treating the indication. As of 2001, the FDA had approved gabapentin as an anticonvulsant and as a pain-reliever for patients with shingles. Scientific evidence supported its use for social anxiety, migraine prevention and certain diabetic conditions. But doctors commonly prescribed it to treat bipolar disorder and chronic pain, uses not evidenced by adequate scientific scrutiny.

Stafford said better communication and education for both the physician and patient about off-label use is crucial to good health care.

“Patients as well as physicians need to ask what’s the level of evidence for using a specific drug for a specific condition,” Stafford said. “Empowering patients to ask about the level of supporting evidence and to have the physicians adequately respond to these questions will improve patient care.”

http://med.stanford.edu/