Comparison of two methods of presenting risk information to patients about the side effects of medicines.
OBJECTIVE
To determine whether the use of verbal descriptors suggested by the European Union (EU) such as "common" (1-10% frequency) and "rare" (0.01-0.1%) effectively conveys the level of risk of side effects to people taking a medicine.


METHODS
Randomised controlled study with unconcealed allocation.


METHODS
120 adults taking simvastatin or atorvastatin after cardiac surgery or myocardial infarction.


METHODS
Cardiac rehabilitation clinics at two hospitals in Leeds, UK.


METHODS
A written statement about one of the side effects of the medicine (either constipation or pancreatitis). Within each side effect condition half the patients were given the information in verbal form and half in numerical form (for constipation, "common" or 2.5%; for pancreatitis, "rare" or 0.04%).


METHODS
The estimated likelihood of the side effect occurring. Other outcome measures related to the perceived severity of the side effect, its risk to health, and its effect on decisions about whether to take the medicine.


RESULTS
The mean likelihood estimate given for the constipation side effect was 34.2% in the verbal group and 8.1% in the numerical group; for pancreatitis it was 18% in the verbal group and 2.1% in the numerical group. The verbal descriptors were associated with more negative perceptions of the medicine than their equivalent numerical descriptors.


CONCLUSIONS
Patients want and need understandable information about medicines and their risks and benefits. This is essential if they are to become partners in medicine taking. The use of verbal descriptors to improve the level of information about side effect risk leads to overestimation of the level of harm and may lead patients to make inappropriate decisions about whether or not they take the medicine.
Knapp
P
P
Pharmacy Practice and Medicines Management Group, University of Leeds, Leeds LS2 9JT, UK. p.r.knapp@leeds.ac.uk
Raynor
D K
DK
Berry
D C
DC
D000328:Adult; D000368:Aged; D000069059:Atorvastatin; D006348:Cardiac Surgical Procedures; D003142:Communication; D032882:Comprehension; D003248:Constipation / Q000139:chemically induced; D004346:Drug Information Services; D005260:Female; D006538:Heptanoic Acids / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000009:adverse effects* / Q000627:therapeutic use; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000517:prevention & control; D010195:Pancreatitis / Q000139:chemically induced; D010353:Patient Education as Topic / Q000379:methods*; D010817:Physician-Patient Relations; D011758:Pyrroles / Q000009:adverse effects* / Q000627:therapeutic use; D018570:Risk Assessment / Q000379:methods*; D019821:Simvastatin / Q000009:adverse effects* / Q000627:therapeutic use; D009626:Terminology as Topic
D006538:Heptanoic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D011758:Pyrroles; D000069059:Atorvastatin; D019821:Simvastatin