Temporal trends in antihypertensive drug prescriptions in Canada before and after introduction of the Canadian Hypertension Education Program

Abstract

Objective: Poor control of hypertension is a world-wide health issue. In 1999, the Canadian Hypertension Education Program (CHEP) was launched to annually develop and implement evidence-based hypertension guidelines in an effort to improve hypertension control rates. This study was designed to examine temporal trends in antihypertensive drug prescribing and to explore whether drug prescriptions changed after initiation of the new CHEP guideline process.

Design and methods: We used longitudinal Canadian dispensing data (from the IMS CompuScript database; IMS Health, Pointe-Claire, Quebec) to examine antihypertensive prescriptions in the 3 years prior to and the 3 years following introduction of the new CHEP process. To control for temporal changes in the incidence of other cardiovascular conditions for which antihypertensive agents may be prescribed for their non-blood pressure-lowering effects (for example, angiotensin-converting enzyme (ACE) inhibitors for heart failure or coronary artery disease), prescription rates for digoxin, loop diuretics, and nitrates were also examined.

Results: Prescriptions for all antihypertensive agents increased significantly between 1996 and 2001 [11% for thiazides, 45% for beta-blockers, 68% for ACE inhibitors, 19% for calcium channel blockers, and 4332% for angiotensin receptor blockers (ARBs)]. Loop diuretic prescriptions increased 27%, but prescriptions for digoxin (-19%) and nitrates (-8%) declined over this time frame. Time series analyses demonstrated increases in the prescription growth rate for all four antihypertensive drug classes recommended in CHEP for the period 1999-2001 compared with 1996-1998, which were statistically significantly and of substantial magnitude (absolute annual increase in prescription growth rate of 4.6% (95% confidence interval 3.5-5.9%) for thiazides, 3.0% (1.8-4.2%) for beta-blockers, 8.2% (6.7-9.7%) for ACE inhibitors, and 6.1% (4.4-7.8%) for calcium channel blockers). The growth rate in nitrate prescriptions did not significantly change [1.1% (-0.6 to +3.0%)] and, although the changes in growth rate for loop diuretics [4.7% (3.2-6.3%)] and digoxin [2.1% (0.6-3.5%)] were statistically significant, they were of smaller magnitude than the changes in the four recommended antihypertensive agents. Similar results were observed when analysis was restricted to new prescriptions only.

Conclusions: Prescriptions for all antihypertensive drugs increased substantially in Canada between 1996 and 2001; the rate of increase was significantly greater after 1999 for all four drugs recommended as first-line therapy in the annual CHEP guidelines. This preliminary data is encouraging, but a national survey of blood pressure control is needed to fully evaluate the impact of the new Canadian guideline process.