• elderly;
  • herb/drug interactions;
  • on-line prescription records;
  • over-the-counter medication;
  • personal electronic medicine profile;
  • pharmacoepidemiology



To assess possible origins of harmful interactions in elderly patients arising from the current absence of information on over-the-counter (OTC) medicines in the Danish ‘on-line prescription record’.


Information on current use of prescription drugs and OTC medicinal products (non-prescription drugs, herbal medicine, dietary supplements, and others) was collected by home visit interviews. The latter OTC products were not listed in an on-line prescription record that covered the previous two years. Information on interactions between OTC medicines and between OTC products and prescription drugs was obtained from the Danish National Drug Interaction Database.


Of the 309 patients recruited (median age 75 years, interquartile range (IQR) 70–81), 229 (74%) used 568 OTC medicines not listed in the Danish ‘on-line prescription record’, amongst which we identified 166 potential interactions - between OTC treatments or between OTC and prescription drugs. Fifty percent of patients taking OTC medicines were exposed to potential interactions, i.e. one to three instances per patient. Twenty-five percent of patients exposed to interactions experienced interaction listed as ‘Can be used with certain precautions’.


The absence of information on OTC products in an on-line prescription record entails a risk of overlooking interactions in elderly patients. Such products should be included in on-line medication records to prevent adverse effects from interactions. However, online medication records are not available in all countries and as inclusion of data on OTC drugs seem not to be feasible presently. Still, it is highly recommended that the patient's drug list is reviewed on a regular basis. Copyright © 2012 John Wiley & Sons, Ltd.