Persistence to antihypertensive drug classes: A cohort study using the Swedish Primary Care Cardiovascular Database (SPCCD)

The aim was to study persistence to, and switching between, antihypertensive drug classes and to determine factors associated with poor persistence.This was an observational cohort study. The Swedish Primary Care Cardiovascular Database includes data from medical records, socioeconomic data, filled prescriptions, and hospitalizations from national registries for 75,000 patients with hypertension. Patients included in the study were initiated on antihypertensive drug treatment in primary healthcare in 2006 to 2007. We defined class persistence as the proportion remaining on the initial drug class, including 30 days of gap. Patients with a filled prescription of another antihypertensive drug class after discontinuation of the initial drug, including 30 days of gap, were classified as switchers. Persistence to the various drug classes were compared with that for diuretics.We identified 4997 patients (mean age 6012 years in men and 63 +/- 13 years in women). Out of these, 95 (2%) filled their first prescription for fixed combination therapy and 4902 (98%) for monotherapy, including angiotensin converting enzyme inhibitors (37%), angiotensin receptor blockers (4%), beta blockers (21%), calcium channel blockers (8%), and diuretics (28%). Persistence to the initial drug class was 57% after 1 year and 43% after 2 years. There were no differences in persistence between diuretics and any of the other antihypertensive drug classes, after adjustment for confounders. Discontinuation (all adjusted) was more common in men (P=0.004), younger patients (P<0.001), those with mild systolic blood pressure elevation (P<0.001), and patients born outside the Nordic countries (P<0.001). Among 1295 patients who switched drug class after their first prescription, only 21% had a blood pressure recorded before the switch occurred; and out them 69% still had high blood pressures.In conclusion, there appears to be no difference in drug class persistence between diuretics and other major antihypertensive drug classes, when factors known to be associated with poor persistence are taken into account.