Antibiotics kill bacteria, not the viruses that cause the common cold and the flu. Yet doctors frequently overprescribe them—out of habit or to satisfy patients' demands—fueling antibiotic resistance.

The U.S. Centers for Disease Control and Prevention reports that up to 50 percent of antibiotic prescriptions in the U.S. are unnecessary or not optimally effective as prescribed.

One new approach may help curb the drugs' overuse. A recent randomized controlled study reported that having clinicians sign a letter pledging to “avoid prescribing antibiotics when they are likely to do more harm than good” reduced inappropriate antibiotic use during flu season. Pledged physicians reduced prescribed antibiotics by about one third compared with unpledged ones. The findings appeared online January 27 in JAMA Internal Medicine.

In the study, seven clinicians—doctors or nurse-practitioners—signed a poster-size commitment to follow prescription guidelines. The letter, which was displayed in exam rooms, also explained that antibiotics cannot cure colds but do cause side effects and contribute to drug resistance. Seven other clinicians served as controls and did not sign a letter or alter their normal practices.

Providers who signed the commitment letter reduced unnecessary prescriptions by about one fifth during the intervention period, whereas those who did not sign a poster increased their inappropriate prescribing rates by about one fifth. Still, even the poster-signing clinicians appear to have provided antibiotics to patients who did not need them roughly one third of the time.

Previous studies have looked at the effects of posting guideline reminders, but they did not include signed commitment letters and did not report the same level of success. “Our hypothesis is that this commitment device is a key difference between our intervention and past work,” asserts lead author Daniella Meeker, a scientist at Rand Corporation who focuses on health and behavioral economics.

The study does not settle the matter. The findings need to be replicated with a larger group of physicians. Yet if the approach triggers similar responses in other settings, the authors say it could theoretically eliminate 2.6 million unnecessary prescriptions and save $70.4 million in drug costs nationwide.