A study of older patients prescribed opioids by a dentist found 10% were also taking medications that should not be taken with opioids because of the potential for harmful interactions.

“Some of the most concerning negative outcomes of these combinations include overdosing on opioids or falling, which can necessitate a visit to the hospital, which in itself carries greater risk for older adults,” said study author Gregory Calip of the University of Illinois at Chicago in a news release.

The study, published in Pharmacotherapy, analyzed medical, dental and pharmacy claims from 40,800 older adult dental patients who were prescribed opioids. The researchers found 10% were already taking a psychotropic medication, such as anti-anxiety or antidepressant medications. These are particularly dangerous if taken with opioids.

Patients inappropriately prescribed an opioid medication combination by their dentist were 23% more likely to be hospitalized or to visit an emergency department in the 30 days after the dental visit, compared with dental patients who did not receive an opioid prescription.