Putting knowledge into practice: Does information on adverse drug interactions influence people's dosing behaviour?

Adverse drug events relating to drug-drug interactions are a common cause of patient harm. Central to avoiding this harm is the patients' understanding that certain drug combinations present a synergistic risk. Two studies tested whether providing individuals with information about a drug combination that presents a synergistic (cf. additive) risk would elicit higher perceived risk and, therefore, would result in greater precaution in terms of dosing behaviour.

Both studies employed an experimental design.

Participants were presented with a scenario describing how two symptoms of an infection could each be treated by a different drug. In Experiment 1, information about the effects of combining the two drugs was varied: (1) no information, (2) combination elicits an additive risk, or (3) combination elicits a synergistic risk. In Experiment 2, the size of the risk (small or large) and the participant's role (patient or doctor) was also varied.

In both experiments, perceived risk and negative affect increased in response to information about the increased probability of side effects from the drug-drug interaction. Despite these increases, participants did not adjust their drug dosing behaviour in either experiment: Dosing was similar when these interactions were large or small, or when they were due to synergistic or additive effects.

People may struggle to transfer their knowledge of drug-drug interaction risks into decision-making behaviours. Care should be taken not to assume that holding accurate risk perceptions of a drug's side effect will result in decisions that help avoid adverse drug events. Statement of contribution What is already known on this subject? Adverse effects of drug-drug interactions are a cause of hospital admissions and increase morbidity and mortality. Patients' understanding that certain drug combinations present a synergistic risk is crucial to avoid harm. It is not clear whether synergistic drug interactions increase risk perception and influence dosing decisions. What does this study add? Perceived risk and negative affect increased in response to synergistic risk information. Despite these increases, participants did not adjust their drug dosing behaviour. People struggle to transfer their knowledge of drug-related risks into behavioural decisions.