Discussing side effects of over-the-counter medicines: impact of adding percentage data

Discussing side effects with patients continues to be a difficult area of practice. Questions arise as to how many should be mentioned and which ones. The way such information is presented can affect drug-taking decisions. This study examined how over-the-counter (OTC) medicine users are influenced by numerical risk estimates of side effects.

As part of a larger study on patient decision-making, 30 participants aged over 50 years were asked to consider three OTC headache medicines. They responded to one of two headache scenarios, one with symptoms described as mild but common and the other severe but rare. Participants made their selection based on drug efficacy and side effects, at first not linked to occurrence rates and then with this information provided.

Average age was 66.6 years and the majority were female. Most were currently using some form of drug therapy. Drug choices differed in relation to mild versus severe headache scenarios. A stronger preference for drug X (50% effective and two side effects) was evident when the headaches were mild, shifting to a more effective agent (but with more side effects) when more severe. Addition of occurrence rates to the side effects had the greatest effect within the severe headache scenario, where more participants opted for the most effective agent (drug Z at 100% effective but six side effects) upon seeing the numbers. Overall, however, most kept the same drug in spite of the numerical information.

Inclusion of numerical data for side effects did not negatively influence potential OTC medicine users. For most, effectiveness and side effects were the concern before receiving the percentages, while effectiveness became more important when the frequency data seemed to instil a sense of reassurance.