Household Pharmaceutical Accumulation in Southeastern Mexico: A Multidimensional Pharmacoepidemiological Risk Assessment Framework

Background/Objectives: The accumulation of unused and expired pharmaceuticals in households is a growing public health concern with implications for patient safety, rational drug use, and environmental health. However, systematic risk characterization integrating clinical and environmental perspectives at the community level remains limited, particularly in low- and middle-income settings. This study aimed to develop and apply a composite risk index, grounded in an eco-pharmacovigilance framework, for the assessment of health risks associated with accumulated household pharmaceuticals in southeastern Mexico. Methods: A cross-sectional study was conducted in 526 randomly selected households using stratified sampling. Guided in-home medication inventories were performed with participant collaboration, and pharmaceuticals were classified according to the Anatomical Therapeutic Chemical (ATC) system. A composite risk index (CRI = Fr × PR) was developed within an eco-pharmacovigilance framework. The frequency of accumulation (Fr) for each therapeutic group was multiplied by a potential risk score (PR) derived through a structured multidisciplinary expert consensus process integrating clinical toxicity, environmental persistence, and antimicrobial resistance potential. Results: A total of 2184 pharmaceutical units were recorded during the household inventories, of which 28.7% were expired. Expired medications were primarily retained rather than actively used, representing a latent risk for inappropriate self-medication and accidental exposure. The therapeutic groups with the highest CRI values were antihypertensives (CRI = 42.3), antidiabetics (CRI = 37.8), and antibiotics (CRI = 31.5), indicating a relatively higher contribution within the composite risk index framework to overall household pharmaceutical risk. These findings highlight priority therapeutic groups driven by the combined effect of high accumulation frequency, distinct accumulation patterns, and intrinsic hazard. Conclusions: Household pharmaceutical accumulation can be characterized using a composite, eco-pharmacovigilance-based approach that integrates exposure and hazard dimensions. The proposed framework functions as a prioritization tool rather than a precise quantitative measure, enabling the identification of therapeutic groups requiring targeted intervention. Findings should be interpreted as indicative of relative risk patterns rather than precise estimates, given the exploratory design and guided data collection approach. The proposed framework provides a practical tool for prioritizing interventions aimed at improving rational drug use, reducing accumulation, and mitigating environmental impact. Further validation in diverse settings is warranted to strengthen its applicability.