*Purpose: The current study was conducted to determine characteristics that are associated with immunosuppressant (IS) medication adherence among adult recipients of deceased donor heart transplants (TXs) in the U.S.

*Methods: Prescription claims data for IS medications from a single, large national pharmacy chain during 2013-2016 were merged with the Organ Procurement and Transplant Network data. The analysis was limited to adult recipients of deceased donor heart TXs performed within a year (± 90 days) prior to the first fill, and who had >2 pharmacy claims for any IS at least 150 days apart in the 12-months after their first fill during the study period. The analysis was further conditioned on 2-year survival, which resulted in 949 recipients who were TXed between 2011 and 2015. In this analysis, adherence to IS medication was defined as proportion of days covered by pharmacy claims >=90%. A multivariable logistic regression was used to develop an explanatory model using various patient and pharmacy claim variables. The results of the analysis are summarized as odds ratio (OR), 95% confidence limit (CL) of the OR, and p-value.

*Results: 577 (61%) of recipients in the analysis were adherent. Median age at transplant was 55 years and the majority (90%) of recipients had a diagnosis of cardiomyopathy. Table 1 summarizes variables that were associated with adherence with an overall p-value of <0.10. The number of prescriptions for chronic conditions of 8 or more was significantly associated with decreased adherence (OR=0.48; p<0.01). Variables positively associated with adherence included having at least 50% of fills at a TX specialized pharmacy (TSP) (OR=1.59; p<0.01) and receiving some copay assistance (OR=1.33, p=0.09). Hispanic recipients and recipients of “other” ethnic groups were significantly more likely to be adherent compared to white recipients (OR=1.79; p=0.04 and OR=2.48; p=0.02, respectively). Black recipients were no more or less adherent than white recipients.

*Conclusions: In a cohort of adult heart recipients, in which the majority had cardiomyopathy, the number of prescriptions for chronic conditions, filling at a TSP, and ethnicity were significantly associated with IS adherence. As non-adherence to IS medication has been associated with poor post-transplant clinical outcomes, understanding patterns of IS adherence among transplant recipients is essential.

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