INFLUENCES OF EDUCATIONAL INTERVENTIONS AND ADVERSE NEWS ABOUT CALCIUM-CHANNEL BLOCKERS ON FIRST-LINE PRESCRIBING OF ANTIHYPERTENSIVE DRUGSTO ELDERLY PEOPLE IN BRITISH-COLUMBIA

Background The way in which dissemination of evidence changes medical practice needs td be better understood. Controversy about calcium-chan nel blockers (CCB) in the past 3 years has provided a natural experime nt, enabling assessment of the impact of media stories, a national war ning letter, a teleconference, small group workshops, and newsletters on first-line prescribing of antihypertensive drugs. Methods We includ ed all physicians (4403) in British Columbia who prescribed a thiazide diuretic, beta-blocker, inhibitor of angiotensin-converting enzyme (A CE), or CCB as the first antihypertensive agent for 36 507 residents a ged 66 years and over, with no previous or concurrent sign of underlyi ng cardiovascular disease. We used a database covering all prescriptio ns to elderly people to measure the change in proportion of newly trea ted patients who received each class of drug as first-line therapy. We used a matched cohort design for assessment of the teleconference and workshops, a randomised community design for the newsletters, and tim e-series analysis for the media impacts. Findings The proportion of pa tients who received a CCB as first-line therapy declined gradually fro m 22% in early 1994 to 15% in late 1996. This proportion was not affec ted by two waves of adverse news about CCBs in 1995, but fell by 5% fo r 5 months and by 3% for 1 month after two waves in 1996. The proporti on of patients who received either a CCB or an ACE inhibitor as first- fine therapy, contrary to guidelines, was still 42% overall in 1996. T he workshops and newsletters were followed by shifts from first-line C CB to first-line thiazide prescribing. Interpretation Changes in presc ribing practices occur gradually with the accumulation of small impact s from educational interventions and lay media attention.