143. Antibiotic Use for Common Infections in British Columbia and Ontario: A Review of Outpatient Prescribing to Seniors from 2000 – 2018

Background Antimicrobials remain among the most prescribed medications in Canada, with over 90% prescribed in outpatient settings. Older adults (aged ≥65 years) prescribed antimicrobials are particularly vulnerable to adverse drug events and antimicrobial resistance. This study compared annual rates of indication-associated, outpatient prescribing to seniors across two Canadian provinces. Methods All outpatient, oral antimicrobials dispensed to older adults (≥65 years) were identified from administrative health databases, from 2000 to 2018. Antimicrobials were limited to outpatient use only and linked to an indication using a 3-tiered diagnostic hierarchy. When possible, a record of dispensation was matched to a tier 1 indication (always require antibiotics) first. In the absence of a tier 1 indication, priority was given to tier 2 (sometimes require antibiotics), then 3 (never require antibiotics). Prescription rates were calculated per 1000 population, and trends were examined overall, by drug class, and patient demographics. Results Our study included over 18 million individuals (aged ≥65 years) with a total of 23,773,552 antibiotic prescriptions issued to seniors, for common infections. In both provinces, prescribing for tier 1 diagnoses increased over the study period (BC: 44%; ON: 28%). Urinary tract infections accounted for most prescriptions within this tier (ON: 89 prescriptions/1000, BC: 129 prescriptions/1000 population by 2018). Pneumonia-associated prescribing increased by roughly 10% in both provinces. In any given study year, for both provinces, tier 3 diagnosis was the most common reason for antibiotic use, accounting for 50% of all indication-associated antibiotic prescribing. As diagnoses within this tier do not warrant prescribing all antibiotics issued are therefore inappropriate prescriptions. Figure 1. Rates of indication-associated antibiotic use in Canadian seniors, from 2000 to 2018. Conclusion Elevated prescribing to seniors continues across Canadian outpatient settings. Antibiotic prescribing remains an issue of high concern with 50% of all antimicrobials prescribed to seniors, for common infections, used inappropriately. Disclosures All Authors: No reported disclosures