Doctors in Boston measured childhood exposure and poisoning from prescriptions written for adults from 2000 to 2009.
They found that adult medication prescriptions were significantly associated with exposure and poisoning in children of all ages.
The strongest association was for painkillers such as codeine.
The greatest risk was among children ages 5 and younger, followed by 13 to 19-year-olds.
Sixty-percent of the children had been exposed to diabetes drugs and heart medications.
The study is published in the journal Pediatrics.