Impact of Prescription Benefit Coverage Limits on Sevelamer Hydrochloride Adherence for Patients with ESRD

OBJECTIVE: To assess the impact of prescription benefit coverage on medication adherence in Medicare-eligible members diagnosed with end-stage renal disease taking sevelamer hydrochloride. METHODS: This pilot study involved a retrospective analysis of patients with end-stage renal disease taking sevelamer, with an annual cap on brand prescription drug spending compared with those without a cap. We compared sevelamer adherence and discontinuation proportions between the 2 groups of Medicare patients in 2003 and 2004. Medication adherence was calculated based on the proportion of available days covered in relationship to capped versus noncapped pharmacy benefit. RESULTS: Rate ratios showed that in 2003, the patients taking sevelamer under a capped benefit (N = 43) had 27% fewer days of drug use compared with those (N = 88) without a capped benefit (relative risk, 0.73; 95% CI, 0.58-0.93). Similarly, in 2004, those taking sevelamer under the capped benefit (N = 21) had 33% fewer days of drug use compared with those (N = 117) without a capped benefit (relative risk, 0.67; 95% CI, 0.46-0.96). CONCLUSIONS: Medication adherence was significantly lower for patients with a capped brand-name drug benefit. These findings provide insight into potential drug utilization patterns, including for sevelamer, under the Medicare Part D benefit, where members could face significant out-of-pocket expenditures once coverage limits are reached.