Effects of a step-therapy program for angiotensin receptor blockers on antihypertensive medication utilization patterns and cost of drug therapy.

Abstract

Step therapy for angiotensin receptor blockers (ARBs) requiring prior use of angiotensin-converting enzyme inhibitors (ACEIs) is a common cost-containment intervention in managed care. This study was designed to assess the effectiveness of the step-therapy intervention for ARBs, including ARB/hydrochlorthiazide (HCTZ) combinations, as measured by prescription use patterns and antihypertensive drug ingredient costs. Rejected and paid pharmacy claims data were evaluated from 3 health plans with a total membership of approximately 1 million. These plans had implemented a step-therapy intervention for ARBs from May 1, 2001, through February 28, 2003. Patients in the intervention group who had experienced a claim rejection for an ARB within the first 6 months of program implementation (i.e., had had no ACEI [or ACEI/HCTZ combination] or ARB [or ARB/HCTZ] claim in the preceding 3 months) were followed for 1 year after the ARB claim rejection. The rate of initiation of ARB versus ACEI and other outcomes was compared with similar data from a health plan with approximately 2 million members that did not have a step-therapy intervention for ARBs (comparison group). Mean and median total antihypertensive drug ingredient costs per patient and per day of therapy over 12 months were analyzed for the intervention and comparison groups. One pharmacy benefit manager administered the pharmacy benefits for the intervention and comparison health plans during the entire study period from May 1, 2001, through February 28, 2004, and the drug formulary was similar for all health plans. In the step-therapy health plans, before the criterion for 15 months of continuous eligibility was applied, there were 8,904 patients (approximately 0.9% of health plan members) who either attempted and were rejected for an ARB or who newly started ACEI therapy, compared with 44,788 patients (approximately 2.2% of members in the comparison health plan) who newly started ARB or ACEI therapy without the step-therapy intervention. After the eligibility criterion was applied, there were 6,758 intervention health plan members (0.7% of members) and 33,709 comparison health plan members (1.7% of members) in the 2 study groups. In addition to the smaller proportion of total members affected by the intervention in the ARB step-therapy health plans, a smaller proportion of ARB/ACEI patients attempted to obtain an ARB (1,296/6,758 or 19.2%) compared with the health plan without step therapy (8,697/33,709 or 25.8%, P <0.001). Of the 1,296 patients who attempted to obtain an ARB and were rejected in the step-therapy group, 578 patients (44.6%) went through the prior-authorization process and received an ARB as initial therapy, 632 patients (48.8%) received other antihypertensive therapy, and 86 patients (6.6%) did not receive any antihypertensive therapy within the 12-month follow-up period. In the 12 months of follow-up, 51.1% (323/632) of patients in the intervention group who received other antihypertensives as index therapy switched to or added an ARB, and 1,234 of total ACE/ARB patients (n = 6,758, 18.3%) received ARB therapy in the health plan with step therapy compared with 10,498 of 33,709 total ACEI/ARB patients (31.1%) who received ARB therapy in the health plan without step therapy. The mean antihypertensive drug cost per patient was lower in the intervention group ($370.00) than in the comparison group ($445.12; P <0.001), and the average cost per day of antihypertensive drug therapy was 12.8% lower in the step-therapy group ($0.82) than in the comparison group ($0.94). Unadjusted annual cost savings were $75.12 per patient, and ordinary least squares regression analysis showed that the ARB step-therapy intervention was associated with $43.91 in antihypertensive drug cost savings per patient over 12 months. Within 12 months of follow-up, a step-therapy intervention for ARBs was associated with an 18% ratio of ARB users to total ACEI/ARB users compared with a 31% ratio in a comparison health plan without the ARB step-therapy intervention. Approximately 45% of patients who did not receive an ARB as a result of the step-therapy intervention had either switched to or added an ARB within 12 months of the intervention, and almost 7% of patients did not receive any antihypertensive therapy. Antihypertensive drug cost was about 13% lower for the ACEI/ARB patients in the intervention group, creating approximately $368,000 in savings in 1 year or $0.03 per member per month across the 1 million health plan members.