Relationship between antihypertensive medication use and blood pressure control among patients with essential hypertension

Background Despite the efficacy of antihypertensive treatment in lowering blood pressure there are only a few observational studies examining the drug specific effect associated with lowering blood pressure in hypertensive patients. The objective of this study was to investigate antihypertensive drug class-specific association with blood pressure (BP) control. Methods We conducted a retrospective cohort observation of patients who were treated for essential hypertension from January 2005 to June 2009. Medical and pharmacy claims were obtained from Taiwan's National Health Insurance database, while electronic records, including demographic characteristics and clinical information, were retrieved from a disease management program. To determine the degree of medication adherence, we calculated the proportion of days covered (PDC) by filled prescriptions. Patients with BP<140/90 mmHg at two consecutive follow-up medical visits were considered to have good BP control. The associations of drug regimens with BP control were examined using multiple logistic regression models. Results The study subjects comprised a total 12,101 uncomplicated essential hypertensive patients. Overall, 64.4% of patients were considered as adherent. Poor medication adherence was associated with higher odds of having BP> 140/90 (OR=1.54, 1.42-1.67). Obesity (OR=1.36, 1.21-1.53), poly-therapy (OR=1.18, 1.09-1.27) and multiple dosing (OR=1.28, 1.10-1.50) were significant predictors for poor BP control. For patients on monotherapy, the use of angiotension receptor blocker (ARB) / angiotension converting enzyme inhibitor (ACEI) or calcium channel blocker (CCB) conferred higher risk for poor BP control, compared with beta-blocker. Conclusion Our observation study demonstrates that poor adherence and therapeutic regimens are associated with poor BP control.