More than one of seven prescriptions for common drugs are for off-label uses lacking scientific support, a study out Tuesday suggests.
Drug makers seek Food and Drug Administration approval for specific uses of their products and conduct trials to test their drugs’ safety and effectiveness in patients with specific conditions. But once the FDA approves a drug for one use doctors can prescribe it for whatever they want.
The new study used data from the 2001 IMS Health National Disease and Therapeutic Index to define prescribing patterns for 160 commonly prescribed drugs, representing slightly more than half of all prescriptions collected by IMS Health, which provides prescription market data for drug and biotech companies. IMS Health collects information about prescribing and diagnoses from a random sample of office-based doctors.
Study authors determined whether the prescription was for an approved or off-label use. If off-label, they then assessed the level of supporting scientific evidence. Their reference was the DRUGDEX system, a nationally recognized comprehensive summary of evidence for approved and off-label uses of prescription drugs.
In 2001, an estimated 150 million prescriptions or 21% for the 160 common drugs were for off-label use, the authors write in the Archives of Internal Medicine.
About 15% of prescriptions were for off-label uses that lacked scientific support, the study found. “It was surprising that three-quarters of off-label use was in the absence of strong evidence,” says senior author Randall Stafford, assistant professor of medicine at Stanford Prevention Research Center.
Off-label prescribing was least common among drugs used to control blood sugar in diabetes, pain-relievers and cholesterol-lowering drugs. It was most common among heart drugs (excluding those for cholesterol and high blood pressure) and anti-convulsants, a type of seizure medication.
It’s not clear why some drugs and types of drugs were more likely to be prescribed for unsupported off-label uses than others. The age of the drug, direct-to-consumer advertising or the company that made it made little difference, researchers said.
One explanation might be that “both physicians and patients have misunderstood the role of the FDA,” Stafford says. “I think there’s sort of a presumption that if a drug has made it onto the market, the FDA has vouched for its safety and efficacy for all of its potential uses.”
Patients should ask their doctors whether a prescription is off-label and, if so, whether there are good data to support it, he says.
In some cases, Stafford notes, scientific evidence for off-label use is strong, but, because the drug is generic, no maker stands to profit by pursuing FDA approval for a new use.
Vanderbilt pharmacologist Alastair Wood suggests since patients often have multiple health problems, some off-label prescribing in the study actually might have been for approved uses that doctors had not mentioned.
Still, Wood agreed that many treatment decisions lack scientific support. “We need to do a better job, I think, of pushing people to base the practice of medicine on evidence, rather than anecdote.”