This study examined behavioural intention to dispose of unused medicines using a comprehensive model integrating the theory of planned behaviour (TPB), with knowledge as a driver of personal norms; attitudes, personal norms, and perceived busyness as additional drivers of behavioural intention; and perceived convenience as a moderator. The model was tested with data collected from 204 respondents using the partial least squares technique. Knowledge about the proper disposal of unused medicines was recognized as a strong predictor of personal norms and attitudes towards proper disposal of waste medications. The results showed that attitudes, personal norms, perceived busyness, and perceived behavioural control have significant effects on intention to dispose of unused medicines. Furthermore, perceived convenience moderates the impacts of attitude, personal norms, and perceived behavioural control on intention to dispose of unused medicines. The extended TPB explained 55.7% of the variance of intention to dispose of unused medicines properly. Our results indicate the importance of integrating additional variables into the TPB to enhance its explanatory power in predicting behavioural intention. The results suggest to governments that in order to implement planned programs for proper collection and destruction of waste medication, a plan is needed to enhance public knowledge on the impacts of improper medication waste disposal on the environment, and also that collection points should become accessible for anyone.
Keywords: Behavioural intention; Medicine disposal; Perceived busyness; Perceived convenience; Pharmaceutical; Pharmacopollution; Reverse logistics; Unused medicines.