Influences of educational interventions and adverse news about calcium-channel blockers on first-line prescribing of antihypertensive drugs to elderly people in British Columbia.
BACKGROUND
The way in which dissemination of evidence changes medical practice needs to be better understood. Controversy about calcium-channel blockers (CCB) in the past 3 years has provided a natural experiment, enabling assessment of the impact of media stories, a national warning letter, a teleconference, small group workshops, and newsletters on first-line prescribing of antihypertensive drugs.


METHODS
We included all physicians (4403) in British Columbia who prescribed a thiazide diuretic, beta-blocker, inhibitor of angiotensin-converting enzyme (ACE), or CCB as the first antihypertensive agent for 36,507 residents aged 66 years and over, with no previous or concurrent sign of underlying cardiovascular disease. We used a database covering all prescriptions to elderly people to measure the change in proportion of newly treated 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 time-series analysis for the media impacts.


RESULTS
The proportion of patients who received a CCB as first-line therapy declined gradually from 22% in early 1994 to 15% in late 1996. This proportion was not affected by two waves of adverse news about CCBs in 1995, but fell by 5% for 5 months and by 3% for 1 month after two waves in 1996. The proportion of patients who received either a CCB or an ACE inhibitor as first-line therapy, contrary to guidelines, was still 42% overall in 1996. The workshops and newsletters were followed by shifts from first-line CCB to first-line thiazide prescribing.


CONCLUSIONS
Changes in prescribing practices occur gradually with the accumulation of small impacts from educational interventions and lay media attention.
Maclure
M
M
Pharmacare, British Columbia Ministry of Health, Victoria, Canada. mmaclure@bcsc02.gov.bc.ca
Dormuth
C
C
Naumann
T
T
McCormack
J
J
Rangno
R
R
Whiteside
C
C
Wright
J M
JM
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000368:Aged; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D000959:Antihypertensive Agents / Q000009:adverse effects*; D001581:Benzothiadiazines; D001955:British Columbia; D002121:Calcium Channel Blockers / Q000009:adverse effects*; D004232:Diuretics; D011307:Drug Prescriptions; D004502:Education, Medical, Continuing / Q000379:methods*; D019317:Evidence-Based Medicine; D006801:Humans; D008402:Mass Media; D010818:Practice Patterns, Physicians'; D049993:Sodium Chloride Symporter Inhibitors / Q000627:therapeutic use
D000319:Adrenergic beta-Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors; D000959:Antihypertensive Agents; D001581:Benzothiadiazines; D002121:Calcium Channel Blockers; D004232:Diuretics; D049993:Sodium Chloride Symporter Inhibitors