Person-Level Correlates of Nonadherence to Co-Medication in Spanish Heart Transplant Recipients

Background: Nonadherence to heart transplantation-related medications involves both immunosuppressant drugs and co-medications; yet the correlates of heart transplantation patients’ overall medication nonadherence remain unclear. Objectives: We aimed to (1) describe nonadherence to both immunosuppressive and co-medication among Spanish heart transplantation patients, (2) to identify individual-level predictors of co-medication nonadherence, and (3) to describe nonadherence to non-pharmacological advice (eg, sun protection, physical activity, alcohol use) and clinical practice patterns of transplant centers. Methods: For this multicenter cross-sectional study, we surveyed 224 adult patients attending 5 Spanish centers 1 to 5 years post-transplantation. We assessed nonadherence to immunosuppressants and co-medications using the Basel Assessment of Adherence to Immunosuppressive Medication Scale (BAASIS © ). Correlates of nonadherence to co-medications were derived from the Integrative Model of Behavioral Prediction using self-report instruments, as were non-pharmacological treatment adherence and treatment centers’ practice patterns. Supported by causal mapping, multiple logistic regression analysis allowed adjustment for relevant confounders. Results: Nonadherence prevalence was 16.5% for co-medications (range across centers: 7.4%-25.0%), versus 9.4% (range: 2.6%-22.2%) for immunosuppressants. Adherence support varied across centers. Barriers to immunosuppressant nonadherence predicted co-medication nonadherence (odds ratio = 11.80; 95% CI, 2.59-53.69). Nonadherence to non-pharmacological treatments, particularly sunscreen use (59.3%) and physical activity (31.8%), were also common. Conclusions: Post-heart transplantation co-medication nonadherence surpasses immunosuppressant nonadherence. Barriers to immunosuppressant adherence strongly predict co-medication nonadherence. While no direct causal relationship is clear, immunosuppressant nonadherence may prove useful for identifying patients prone to co-medication nonadherence.