958T he complexity of blood pressure regulatory mechanisms suggests that combined use of antihypertensive drugs with different pharmacological actions to achieve synergism is a rational approach to obtain optimal control of hypertension.1 Recent hypertension guidelines also recommend initiating antihypertensive therapy with 2 drugs if blood pressure is >20 mm Hg above systolic goal or >10 mm Hg above diastolic goal. 2,3 In most countries, more than half of treated patients with hypertension are indeed on ≥2 drugs. 2,4 Moreover, patients with hypertension are often associated with other cardiovascular risk factors and comorbidities, which may further increase the pill burden. Therefore, polypharmacy and resultant noncompliance are both frequently encountered problems in the management of hypertension.
5To simplify complex medical regimens and improve adherence, the use of combinations of ≥2 antihypertensive drugs at fixed doses in a single tablet, commonly called fixed-dose combinations or single-pill combinations (SPCs), has been advocated in several hypertension guidelines. 2,3,6,7 In a recent meta-analysis of studies comparing the administration of antihypertensive SPCs with their corresponding free-drug combinations, the compliance rate was improved by 21% in patients receiving SPCs. 8 However, most evidences showing that SPCs were associated with improved adherence are from cohort studies with parallel group comparisons and without adjustments for comorbidities and concomitant medications. The only relevant randomized crossover studies were of small size and conducted ≈3 decades ago.9,10 In other words, there are no reported studies assessing the effects of SPCs on adherence in real-world patients with hypertension switched from free-drug combinations to SPCs. Given that SPCs have also been accused of reduced flexibility in dosing and possible increased adverse effects, it is of importance to examine whether the common practice of switching from free-drug combinations to SPCs does invariably achieve better adherence in diverse patients with hypertension.The computerized claims database of the National Health Insurance (NHI) in Taiwan provides us a unique opportunity to carry out such a study. In this study, we aimed to assess (1) the effect of switching from antihypertensive free-drug Abstract-There are no reported studies assessing the effects of fixed-dose single-pill combinations (SPCs) of antihypertensive drugs on adherence in real-world patients with hypertension switched from free combinations to the corresponding SPCs. In this retrospective cohort study with a 1-year mirror-image design, a total of 896 patients who had been prescribed with an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker and a thiazide-type diuretic within the preceding 12 months of the index (switching) date and the corresponding SPC within 12 months after the index date were included by using the Taiwan National Health Insurance database from January 2001 to December 2007. Adherence was measured by medicati...