Association of cinacalcet adherence and costs in patients on dialysis

In addition to negative impacts on clinical effectiveness in treating secondary hyperparathyroidism, low adherence to cinacalcet may have negative impacts on healthcare costs. This study assessed the relationship between medication adherence and healthcare costs among US patients on dialysis given cinacalcet to manage secondary hyperparathyroidism.

Retrospective cohort study of patients who were receiving dialysis with an initial cinacalcet prescription between January 2004 and April 2010 and who survived ≥12 months. Longitudinal, integrated medical, and pharmacy claims data from the MarketScan? database were used to calculate medication possession ratios (MPR) over 12 months and to examine the association of adherence with inpatient, outpatient, emergency room, outpatient medication, and total costs while controlling for patient characteristics, co-morbid medical conditions, and concomitant medication MPR in a multivariate regression model. Patients were dichotomized as adherent (<180 days refill gap) or non-adherent (≥180 day refill gap). Adherent patients were further dichotomized as low adherent (<0.8 MPR) and high adherent (≥0.8 MPR).

The final study cohort included 4923 patients. After 12 months, 46% were non-adherent, 27% were low adherent, and 28% were high adherent. Greater cinacalcet adherence was associated with significantly lower inpatient costs with cost-savings of a greater magnitude than the increased medication costs.

This study demonstrated that low adherence to cinacalcet, which may be associated with undesirable clinical and health-economic outcomes, is common. Despite limitations inherent in retrospective studies of claims databases, such as unobserved confounding, non-discrimination between prescription fill and actual use, and not knowing the reasons for non-adherence, these results suggest that inpatient cost savings of $8899, more than offset higher medication costs of $5858 associated with increased cinacalcet adherence.