Influences of educational interventions and adverse news about calcium-channel blockers on first-line prescribing of antihypertensive drugs to elderly people in British Columbia

Lancet. 1998 Sep 19;352(9132):943-8. doi: 10.1016/S0140-6736(97)11390-3.


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.

Findings: 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.

Interpretation: Changes in prescribing practices occur gradually with the accumulation of small impacts from educational interventions and lay media attention.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenergic beta-Antagonists / therapeutic use
  • Aged
  • Angiotensin-Converting Enzyme Inhibitors / therapeutic use
  • Antihypertensive Agents / adverse effects*
  • Benzothiadiazines
  • British Columbia
  • Calcium Channel Blockers / adverse effects*
  • Diuretics
  • Drug Prescriptions*
  • Education, Medical, Continuing / methods*
  • Evidence-Based Medicine
  • Humans
  • Mass Media*
  • Practice Patterns, Physicians'*
  • Sodium Chloride Symporter Inhibitors / therapeutic use


  • Adrenergic beta-Antagonists
  • Angiotensin-Converting Enzyme Inhibitors
  • Antihypertensive Agents
  • Benzothiadiazines
  • Calcium Channel Blockers
  • Diuretics
  • Sodium Chloride Symporter Inhibitors