Assessing Medication Adherence in Solid-Organ Transplant Recipients

Objectives: We sought to determine and compare the prevalence of nonadherence in lung, kidney, and liver transplant recipients, and identify potential risk factors for nonadherence. Materials and Methods: This cross-sectional, single-center, retrospective cohort study, evaluated 225 outpatient lung, kidney, and liver transplant recipients' adherence to immunosuppressant medication. Based on immunosuppressant dosages and dispensing records, medication possession ratio (days of medication supplied/actual days) and gaps in prescription refills (> 30-day lapse between expected depletion of supply and next refill) were used as surrogate markers in assessing adherence for 2 years. Patients were adherent to their immunosuppressant medication regimens if their medication possession ratio was >= 80%. Results: The mean age of the subjects was slightly greater than 50 years of age, and they were a median of 2.0, 1.3, and 1.1 years posttransplant at the start of data collection for lung, kidney, and liver recipients. Overall medication possession ratios were 95.4% +/- 7.5%, 95.9% +/- 7.6%, and 92.7% +/- 12.3% in our lung, kidney, and liver recipients. Only 7.1% of patients had a medication possession ratio lower than 80%, which was the cutoff for nonadherence. No statistical analyses were performed to identify potential factors for nonadherence because of the small number of nonadherent patients. Conclusions: Immunosuppressant medication adherence at our center was high for all 3 organ cohorts, as measured by a medication possession ratio of 80% or better. Further study is needed to evaluate immunosuppressant adherence over time after transplant, and confirm the clinical factors that optimize adherence in high-risk patients.