Abstract
Purpose: Single-pill-combination (SPC) antihypertensive drug products have been shown to improve compliance but are associated with higher acquisition costs. This study compared the clinical and economic outcomes associated with the use of an SPC of amlodipine/valsartan (trade name Exforge) with the outcomes from conventional combination therapy in patients failing to respond to initial monotherapy with either a dihydropyridine calcium channel blocker (DHP-CCB) or an angiotensin receptor blocker (ARB). Design: We conducted a retrospective cohort study of hypertensive patients failing to respond to monotherapy with either a DHP-CCB or an ARB who were switched to an SPC of amlodipine/valsartan (SPC group) or to treatment that could not include any SPC (control group). The groups were matched for age, gender, race, baseline blood pressure (BP), and co-morbidities. The primary outcomes of the study included the proportion of patients achieving BP targets, the absolute change in BP from baseline, the proportion of patients discontinuing drug therapy because of side effects, the proportion of patients non-compliant with drug therapy, and health care resource utilization and costs. Principal findings: Fifty-eight SPC patients achieved BP targets compared with 47 control patients (P = 0.119). The absolute reduction in BP was significantly greater in the SPC group (-22.8 ± 6.9/-19.3 ± 5.2 mmHg) than in the control group (-20.6 ± 6.4/-17.8 ± 5.6 mmHg) (P <0.03). Significantly fewer patients discontinued anti-hypertensive therapy because of side effects and noncompliance in the SPC group compared with the control group (both P = 0.042). SPC patients accrued fewer clinic visits, laboratory tests, and electrocardiograms but had higher drug acquisition costs. Median medical therapy costs were significantly lower in the SPC group at the end of the 6-month follow-up, primarily because of lower costs for clinic visits. Conclusion: The use of the SPC of amlodipine/valsartan was associated with greater absolute BP reductions and fewer antihypertensive drug discontinuations because of side effects and noncompliance compared with the use of the individual drugs. Although the acquisition cost of the SPC was greater than that of the individual drugs, SPC combination therapy resulted in fewer clinic visits, laboratory tests, and electrocardiograms. As a result, the total cost of SPC therapy was significantly less than that associated with the use of the individual drug components.