Assessment of adherence, persistence, and costs among valsartan and hydrochlorothiazide retrospective cohorts in free-and fixed-dose combinations.

OBJECTIVES: To assess medication adherence, persistence, and costs between cohorts of patients in managed care settings using a fixed-dose combination (FDC) or individual components (IC) of valsartan and hydrochlorothiazide in an insurance claims database.
METHODS: Medical and prescription claims for hypertensive patients using a combination of valsartan and HCTZ were identified from the IHCIS National Managed Care Benchmark Database via a retrospective cohort analysis. Study subjects had at least 110 days prior to start of study medications during which no other antihypertensive medications were prescribed, and were followed for 12 months. Claims for 8711 adult patients were analyzed for adherence, persistence and costs. General linear regression was conducted to detect differences in adherence among groups. Covariates included age, gender, persistence, number on concomitant cardiovascular drugs, and number of cardiovascular diagnoses.
RESULTS: Most subjects used an FDC product (N=8150, 93.6%) vs. the IC (N=561, 6.4%). The FDC group had a larger portion of males and less concomitant cardiovascular medications or disease. A random sample of 1628 of the FDC subjects had improved values for medication adherence compared to the IC group (62.1 vs. 53.0%, p<0.001) and persistence values were improved at both 180 days (73 vs. 28%, p<0.001) and 365 days (54 vs. 19%, p<0.001). Both prescription drug costs ($1587 vs. $2050, p<0.001) and medical costs ($3343 vs. $3817, p<0.001) were lower in the FDC cohorts.
CONCLUSIONS: The use of fixed-dose therapy in hypertension may lead to increased adherence and persistence with a positive financial impact on both prescription and total medical costs. As with any retrospective claims database analysis, unobserved systematic differences between the two medication groups may exist.