U.S. physician knowledge of the FDA-approved indications and evidence base for commonly prescribed drugs: results of a national survey.

Purpose: The Food and Drug Administration (FDA) regulates prescription drug marketing, not prescribing. However, off-label use is common, often lacks supporting evidence, and may expose patients to unwarranted risk. We sought to determine physicians' knowledge of the FDA-approved indications of commonly prescribed drugs, and to assess whether physicians' belief that an indication is FDA-approved increases with level of evidence supporting such use.

Methods: We conducted a national random sample mail survey of 599 primary care physicians and 600 psychiatrists from November 2007 to August 2008. Physicians were presented with 14 drug-indication pairs (e.g., gabapentin [Neurontin] for diabetic neuropathy) that varied in their FDA-approval status and levels of supporting evidence.

Results: The adjusted response rate was 47%, respondents were similar to non-respondents, and physicians commonly prescribed the drugs examined. The average respondent accurately identified the FDA-approval status of just over half of the drug-indication pairs queried (mean 55%; median 57%). Accuracy increased modestly (mean 60%, median 63%) when limited to drugs the respondent reported having prescribed during the previous 12 months. There was a strong association between physicians' belief that an indication was FDA-approved and greater evidence supporting efficacy for that use (Spearman's rho 0.74, p < 0.001). However, 41% of physicians believed at least one drug-indication pair with uncertain or no supporting evidence (e.g., quetiapine [Seroquel] for dementia with agitation) was FDA approved.

Conclusions: These findings highlight a pressing need for more effective methods to inform physicians about the evidence base, or lack thereof, for drugs they prescribe off label.