Stepped care for hypertension: are the assumptions valid?

OBJECTIVE

To examine whether the choice of initial antihypertensive medication is associated with patient withdrawal from therapy among a large cohort of newly diagnosed hypertensive individuals receiving medical care in actual practice.

DESIGN

The records of the outpatient prescription drug plan of Saskatchewan, Canada, were searched for individuals with a diagnosis of essential hypertension who were receiving at least one antihypertensive drug between January 1989 and December 1994. Persistence was defined, and records were classified by class of initial antihypertensive agent prescribed.

SUBJECTS

In all, the records of over 79,000 individuals with a diagnosis of hypertension and an antihypertensive drug prescribed between 1990 and 1994 were evaluated. Persistence with therapy was considered in a subset of newly diagnosed patients, observed for at least 6 months, and receiving an initial prescription from one of four major categories of antihypertensive agents.

RESULTS

Among newly diagnosed patients, diuretics and angiotensin converting enzyme (ACE) inhibitors were the most common initial medication. ACE inhibitors were associated with the highest persistence rates after 1 year of follow-up (83%), followed by calcium antagonists (81%), diuretics (78%) and beta-blockers (74%) (P < 0.001). These results were unchanged in a Cox proportional hazards model which controlled for confounding by age, sex and proxy measures for prior health status.

CONCLUSIONS

A significant proportion of newly diagnosed patients withdraw from therapy within the first year, and this withdrawal seems to be related to the choice of initial antihypertensive agent. These results suggest that recommendations for using stepped care in hypertension management may not be optimal if the initial agent prescribed is associated with decreased levels of persistence with therapy.