Open Access

Katharina Quaschning, Mirjam Koerner, Markus Antonius Wirtz

• Abstract Background Based on the theoretical model of medication adherence (WHO, 2003), the aims of the study were (1) to develop and test a theory-based multidimensional model for the predictive power of barriers to and facilitators of medication adherence and (2) to identify the mediating effects of barriers to medication adherence on drug-related patient outcomes (barrier “MedAd- “: forget; facilitator “MedAd + ”: regular intake). Methods Within a cross-sectional study entitled “Increasing medication adherence to improve patient safety in cardiological rehabilitation (PaSiMed)”, the model was evaluated in structural analytical terms based on data collected online of N  = 225 patients with cardiometabolic diseases. The revised “Freiburg questionnaire on medication adherence (FF-MedAd-R)" was used to measure the latent constructs (e.g., facilitator: communication; barrier: reservations).” Results The structural equation model proved to exhibit an appropriate data fit (RMSEA: .05; CFI: .92). For all first-order facilitators of medication adherence, a high proportion of variance (62–94%) could be explained by the second-order factor “Physician–patient relationship (PPR)”. All paths from “PPR” to the constructs depicting barriers to medication adherence showed significant negative effects. Facilitators (“MedAd + ”) and barriers (“MedAd-”) accounted for 20% and 12% of the variance, respectively, in global items of medication adherence. Whereas “Carelessness” showed a full mediation for “MedAd-”, ‘‘Reservations’’ showed a partial mediation for “MedAd + ”. Conclusions “PPR” is an important predictor of patient medication adherence. The results underline the importance of a trustful physician–patient relationship in reducing barriers and enhancing medication adherence.