Purpose: Few studies have examined the effect of new evidence from clinical trials on physician practice. We took advantage of differences in promotional activity in Canada and the United States for the Heart Outcomes Prevention and Evaluation (HOPE) study and the Randomized Aldactone Evaluation Study (RALES) to determine if publication of new evidence changes practice, and the extent to which promotion influences adoption of new evidence.
Methods: We used longitudinal dispensing data, collected from 1998 to 2001, to examine changes in prescribing patterns for ramipril and other angiotensin-converting enzyme (ACE) inhibitors before and after the HOPE study. We also obtained estimates for promotional expenditures. We stratified analyses by country, to isolate the effect of promotion, and used interrupted time series methods to adjust for pre-existing prescribing trends. Similar analyses were conducted for spironolactone use before and after RALES.
Results: Publication of the HOPE study results was associated with rapid increases in the use of ramipril. After adjusting for pre-existing prescribing trends, ramipril prescribing increased by 12% per month (P = 0.001) in Canada versus 5% per month (P = 0.001) in the United States after the study results were presented and published. One year later, ramipril accounted for 30% of the ACE inhibitor market in Canada versus 6% in the United States. The year before publication of these results, expenditures for detailing increased by 20% in Canada (to 18 US dollars per physician) but decreased by 7% in the United States (to 13 US dollars per physician); the year after publication, spending increased to 27 US dollars per physician in Canada versus 23 US dollars per physician in the United States. In the absence of promotional activity for RALES in either country, publication of results was associated with more modest but similar increases of 2% per month (P = 0.001) in spironolactone use in both countries.
Conclusion: Publication of new evidence is associated with modest changes in practice. Promotional activity appears to increase the adoption of evidence. Rather than relying on the publication of articles and creation of guidelines, those wishing to accelerate the adoption of new evidence may need to undertake more active promotion.