Background: Current German or UK package leaflets do not contain an explicit notice that the listing of side effects does not imply that they are caused by the drug. Causal interpretations by patients and lay people are frequently observed. The authors examined whether health professionals understand that there is not necessarily a causal relation between drug intake and the frequency of side effects and whether adding placebo comparison improves understanding.
Methods: Exploratory survey consisting of eight assessments, each containing 2-6 survey items, and focus groups with one survey sample using questionnaires on adverse reactions in standard package leaflets and modified package leaflets supplemented with placebo comparison. Participants were convenience samples of 379 health professionals including 153 physicians (80 gynaecologists, 124 diabetes experts - physicians, nurses, and others, 39 medical students in their last year at university, 49 first year health science and education students with completed vocational training and professional experience in various health care professions and 87 pharmacists/pharmacy students). They were asked to rate how often the different adverse reactions listed were caused by drug intake. All surveys were carried out within university seminars and postgraduate lectures from April 2014 to June 2015 in Germany. Response rate was 86 % or higher.
Results: Without placebo comparison, the majority of participants responded that the drug causes adverse reactions with the frequency given in the package leaflet or even more often (95 % of health science students, 100 % of medical students, 60 to 80 % of physicians and 66 % of pharmacists/pharmacy students). Simply adding placebo comparison in a table did not prevent misunderstanding. Analysis of focus groups with health science students supported the lack of understanding.
Conclusions: In the present surveys, health professionals had major difficulties understanding frequency information on side effects in package leaflets. The great majority erroneously implied a causal relation between drug intake and the frequency of side effects, even though most side effects listed are symptoms commonly experienced in daily life.