Theory of Planned Behaviour Constructs as Predictors of Antiplatelet Medication Adherence Following Percutaneous Coronary Intervention: A Cross-Sectional Study in Saudi Arabia

Background: Theoretical frameworks are essential for understanding and predicting medication adherence behaviours. The Theory of Planned Behaviour (TPB) posits that behavioural intentions, shaped by attitudes, subjective norms, and perceived behavioural control, are the proximal determinants of behaviour. This cross-sectional study examined associations between TPB constructs and antiplatelet medication adherence among Saudi patients following percutaneous coronary intervention (PCI). Methods: A cross-sectional survey was conducted among 236 Saudi adults post-PCI at two tertiary cardiac centres in Riyadh. TPB constructs (attitude, subjective norms, perceived behavioural control, intention) were assessed using a validated questionnaire. Adherence was measured via the Morisky Medication Adherence Scale-8 (MMAS-8). Hierarchical multiple regression examined associations between TPB constructs and adherence, controlling for demographic and clinical variables. Results: The results demonstrated significant associations with adherence. In the final regression model, intention (β = 0.273, p < 0.001), perceived behavioural control (β = 0.189, p = 0.007), and subjective norms (β = 0.142, p = 0.038) were significantly associated with adherence. Attitude was not significantly associated (β = 0.087, p = 0.194). The TPB constructs explained an additional 18.7% of variance in adherence beyond demographic and clinical factors. Conclusions: The TPB provides a useful framework for understanding antiplatelet adherence patterns in Saudi post-PCI patients. These findings suggest that interventions addressing behavioural intentions, perceived control over medication-taking, and normative influences from significant others may potentially enhance adherence outcomes. Theory-informed nurse-led interventions incorporating strategies such as implementation intentions and family involvement are recommended.