Shorter and longer courses of antibiotics for common infections and the association with reductions of infection-related complications including hospital admissions.

BACKGROUND Antimicrobial resistance is a serious global health concern that emphasises completing treatment course. Recently, the effectiveness of short versus longer antibiotic courses has been questioned. This study investigated the duration of prescribed antibiotics, their effectiveness and associated risk of infection-related complications. METHODS Clinical Practice Research Datalink identified 4 million acute infection episodes prescribed an antibiotic in primary care between January 2014 - June 2014, England. Prescriptions were categorised by duration. Risk of infection-related hospitalisations within 30 days was modelled overall and by infection type. Risk was assessed immediately after or within 30 days follow-up to measure confounders given similar and varying exposure respectively. An interaction term with follow-up time assessed whether hazards ratios (HR) remained parallel with different antibiotic durations. RESULTS The duration of antibiotic courses increased over the study period (5.2-19.1%); 6-7 days were most common (66.9%). Most infection-related hospitalisations occurred with prescriptions of 8-15 days (0.21%), accompanied by greater risk of infection-related complications compared to patients that received a short prescription (HR 1.75 [95% CI 1.54-2.00]). Comparing HRs in the first 5 days versus remaining follow-up showed longer antibiotic courses were no more effective than shorter courses (1.02 [95% CI 0.90-1.16] and 0.92 [95% CI 0.75-1.12]). No variation by infection-type was observed. CONCLUSION Equal effectiveness was found between shorter and longer antibiotic courses and the reduction of infection-related hospitalisations. Stewardship programmes should recommend shorter courses of antibiotics for acute infections. Further research is required for treating patients with a complex medical history.