Effect of initial drug choice on persistence with antihypertensive therapy: the importance of actual practice data

Background: Rational medical decisions should be based on the best possible evidence. Clinical trial results, however, may not reflect conditions in a ctual practice. In hypertension, for example, trials indicate equivalent an tihypertensive efficacy and safety for many medications, yet blood pressure frequently remains uncontrolled, perhaps owing to poor compliance. This pa per examines the effect of initial choice of treatment on persistence with therapy in actual practice. Methods: The authors examined all outpatient prescriptions For antihyperten sive medications filled in Saskatchewan between 1989 and 1994 by over 22 00 0 patients with newly diagnosed hypertension whose initial treatment was wi th a diuretic, beta-blocker, calcium-channel blocker or angiotensin-convert ing-enzyme (ACE) inhibitor. Rates of persistence over the first year of tre atment were com pared. Results: After 6 months, persistence with therapy was poor and differed acc ording to the class of initial therapeutic agent: 80% for diuretics, 85% fo r beta-blockers, 86% for calcium-channel blockers and 89% for ACE inhibitor s (p < 0.007). These differences remained significant when age, sex and hea lth status in the previous year were controlled for. Changes in the therape utic regimen were also associated with lack of persistence. Interpretation: A relation not seen in clinical trials - between persistenc e with treatment and initial antihypertensive medication prescribed - was f ound in actual practice. This relation also indicates the importance of rea l-world studies for evidence-based medicine.