Adherence to antihypertensive agents and blood pressure control in chronic kidney disease.

BACKGROUND: hypertension is a modifiable risk factor in chronic kidney disease (CKD), and medication adherence (MA) is critical in reaching the treatment goals. Patterns of MA for antihypertensive agents and its impact on blood pressure (BP) in CKD practice settings are not well studied.

METHODS: we examined 7,227 CKD patients receiving at least one antihypertensive prescription between 2006 and 2007. Outpatient BP measurements were averaged as high (>130/ 80 mm Hg) versus normal (others). MA was calculated using medication possession ratio (MPR = actual treatment days/total possible treatment days). Good versus Poor MA (MPR ≥ 0.8 vs. <0.8) groups were compared for differences in demographic, co-morbid, and laboratory variables. The relationship between MA and BP was examined by logistic regression.

RESULTS: 4,867/7,227 patients (67%) had Good MA; the frequency of patients with Good MA varied by each drug class (p < 0.0001). MPR declined with worsening CKD (stage III: MPR = 0.83 standard deviation (SD 0.18); stage IV: MPR = 0.78 (SD 0.22); stage V: MPR = 0.75 (SD 0.21); p < 0.0001). Hospitalization episodes also negatively impacted adherence. Only 35% of CKD patients had normal BP. By multivariate analysis, Poor MA was associated with high BP (odds ratio 1.23, 95% confidence interval 1.11-1.37).

CONCLUSIONS: 33% of CKD patients have Poor MA for antihypertensive agents, and MA worsens with declining renal function. Poor MA is associated with a 23% greater risk of uncontrolled hypertension. Monitoring and improving adherence in CKD practice may improve outcomes.