Approximately one in five prescriptions to elderly people is inappropriate, according to a study published in the open access journal PLOS ONE.

The authors of the study, led by Dedan Opondo of the Academic Medical Center in Amsterdam, conducted a systematic review of English-language studies of medication use in the elderly and found that the median rate of inappropriate prescriptions was 20.5%.

Some of the medications with the highest rates of inappropriate use were the antihistamine diphenhydramine, the antidepressant amitriptyline, and the pain reliever propoxyphene.