Abstract 175: The Association between Antihypertensive Medication Drug Class and Adherence: An Electronic Monitoring Study

Abstract

Introduction: Prior studies that rely on pharmacy refill data suggest that there maybe an association between antihypertensive drug class and adherence. We aimed to determine whether there is a relationship between antihypertensive drug class and adherence measured electronically. Methods: We enrolled a sample of 188 participants with treated but uncontrolled hypertension from 2 urban primary care clinics. Adherence was measured during the interval between two clinic visits using a 4-compartment electronic pillbox (MedSignals) that records the date and time each compartment is opened. Adherence was calculated as the percent of days the correct number of doses of a particular medication was taken as prescribed. A mixed effects regression analysis was used to assess the association between drug class and percent adherence using Bonferroni adjusted alpha levels and adjusting for age, gender, ethnicity, number of BP medications/patient, coronary artery disease (CAD), depressive symptoms, and days monitored. Sensitivity analyses adjusted for dosing frequency. Results: The mean (SD) age was 64.2 (9.1) years; 71% were female (134/188); 75% Hispanic (141/188); 14% (27/188) had CAD. A total of 470 BP medications were assessed. On average, participants were monitored 48.3 (40.9) days, took 2.4 (1.0) BP medications each, and had 7.2 (6.0) depressive symptoms. Beta-blockers were the most commonly prescribed drug class (54.8%, 103/188), followed by calcium channel blockers (CCBs; 53.2%, 100/188), diuretics (43.6%, 82/188), angiotensin converting enzyme inhibitors (ACEIs; 40.4%, 76/188), angiotensin receptor blockers (ARBs; 28.7%, 54/188), and other classes (29.3%, 55/188). Beta-blockers and other drug classes had significantly higher dosing frequencies. In the mixed effects analyses, a significant effect for drug class was observed. In the unadjusted model, mean percent adherence was 67.7% for beta-blockers, 73.7% for ARBs, 74.3% for CCBs, 75.4% for diuretics, and 76.3% for ACEIs. In the adjusted model, adherence to beta-blockers was 9.2% (SE 1.4%) lower than diuretics (adj p <0.0001), 8.7% (SE 1.6%) lower than ACEIs (adj p gt 0.30). After adjusting for dosing frequency, no relationship remained between drug class and adherence. Adherence was associated with systolic blood pressure in adjusted regression analyses (B=0.34, SE= 0.08, p <0.0001). Discussion: To our knowledge, this is the first study to compare and electronically monitor several drug classes simultaneously. Adherence was suboptimal for all drug classes and associated with suboptimal BP. Physicians should account for low adherence, particularly to beta-blockers, and the significant effect of dosing frequency when prescribing antihypertensives.