The safety of delayed versus immediate antibiotic prescribing for upper respiratory tract infections.

BACKGROUND: This study aimed to evaluate the clinical safety of delayed antibiotic prescribing for upper respiratory tract infections (URTI), which is recommended in treatment guidelines for less severe cases.

METHODS: Two population-based cohort studies used the English Clinical Practice Research Databank and Welsh Secure Anonymised Information Linkage, containing electronic health records from primary care linked to hospital admission records. Patients with URTI and prescriptions of amoxicillin, clarithromycin, doxycycline, erythromycin or phenoxymethylpenicillin were identified. Patients were stratified according to delayed and immediate prescribing relative to URTI diagnosis. Outcome of interest was infection-related hospital admission in 30 days after.

RESULTS: The population included 1.82 million patients with an URTI and antibiotic prescription. 91.7% had an antibiotic at URTI diagnosis date (immediate) and 8.3% had URTI diagnosis in 1-30 days before (delayed). Delayed antibiotic prescribing was associated with a 52% increased risk of infection-related hospital admissions (adjusted hazard ratio of 1.52, 95% confidence interval 1.43-1.62). The probability of delayed antibiotic prescribing was unrelated to predicted risks of hospital admission. Analyses of Number Needed to Harm showed considerable variability across different patient groups (median with delayed antibiotic prescribing was 1357, 2.5% percentile 295 and 97.5% percentile 3366).

CONCLUSIONS: This is the first large population-based study examining the safety of delayed antibiotic prescribing. Waiting to treat URTI was associated with increased risk of hospital admission, although delayed antibiotic prescribing was used similarly between high and low-risk patients. There is a need to better target delayed antibiotic prescribing to URTI patients with lower risks of complications.