When ADEs occur after discharge, patients may present to an urgent care center, an emergency department, or their primary care provider, Dr. Tamma noted.

As a result, “the (hospital’s) clinicians don’t receive the feedback that the antibiotics they prescribed – sometimes in the setting of knowing they probably weren’t necessary but recommended them ‘just in case’ – led to real harm in a patient,” she said.

Clinicians sometimes forget that antibiotics “are not risk neutral,” Dr. Tamma said. When prescribing an antibiotic, it’s important for physicians to ask themselves whether the potential benefits of the antibiotic outweigh the potential risks for the patient, she said.

In addition to the potential for causing immediate harm, “we need to be very careful in how (antibiotics) are used because if they are prescribed indiscriminately, we will continue to see bacteria evolve and develop resistance to available antibiotics,” she said.

The researchers cautioned that the findings may not reflect the frequency of antibiotic-associated adverse effects that occur elsewhere, because the study hospital’s “robust” antibiotic stewardship program likely reduced overall antibiotic prescriptions and durations of therapy.

The authors’ finding adverse drug events occurring in about one in five hospitalized patients who were exposed to an antibiotic largely confirms those of other studies which have looked at many types of drugs, Dr. David Westfall Bates, who directs the Center for Patient Safety Research and Practice at Brigham and Women’s Hospital in Boston, told Reuters Health by email.

The results “are of interest because they have been done within the era of electronic records, which probably increases the number of adverse drug events which can be found, and because broader-spectrum antibiotics are used (more often) now than previously,” said Dr. Bates, who was not involved in the study.

The study provides a comprehensive and current picture of this issue, he noted, which is important because of the constantly changing spectrum of antibiotics in use.

“More days of therapy increased the risk of adverse drug events, and more judicious use of antibiotics would reduce that risk,” he said.

The study was funded by a grant from Pfizer Independent Grants for Learning and Change and the Joint Commission, and the researchers report no conflicts of interest.