The reasons might be variable prescribing patterns and/or lack of patient compliance Application of CFs to several AAs to back-calculate intake observed good agreement with estimated intake from the prescription data, closer matches were observed in the catchment with the larger population size (Bath) • WBE proved useful in differentiating between consumption vs topical usage and/or direct disposal of unused AA • WBE is superior to prescription data as it provides information on AAs prescribed outside of the monitoring catchment (e.g. antiviral and TB drugs) • Data triangulation (WBE, prescription, and demographics data) provides the most comprehensive approach to AA usage in any given catchment