Antibiotic Choice and Duration Associate with Repeat Prescriptions in Infective Asthma Exacerbations

Background: Patients with asthma who present with lower respiratory tract infections (LRTIs) often receive antibiotics. There is uncertainty about the need for and consequences of antibiotic administration. Objective: To describe the demographic characteristics of and antibiotic prescriptions for adult patients with asthma with LRTI and investigate factors associated with repeat antibiotic courses. Methods: We analyzed prescriptions of antibiotics for LRTIs in UK primary care from 2010 to 2015 using the Optimum Care Database. The primary outcome was a second antibiotic prescription for an LRTI code within 14 days of index prescription, as a proxy of initial treatment failure. A model for repeat prescriptions was derived using univariable and multivariable logistic regression analyses. Results: We assessed 28,289 cases with complete data sets, 6.5% of which received a second antibiotic course. Amoxicillin and clarithromycin respectively were used most commonly as index and second agents. The most frequent course length was 7 days for both index and repeat prescriptions. Multivariable analysis demonstrated that age, index antibiotic and duration, smoking status, location, and number of consultations and oral steroid courses in the previous year were significantly associated with repeat prescriptions. The derived model predicted the binary outcome adequately (Cox-Snell R2, 0.012; area under curve, 0.62; 95% CI, 0.61-0.63). Comorbidities, vaccinations, asthma treatment, and number of exacerbations were significant only in the univariable analysis. Conclusions: The current index prescribing preference of 7 days of amoxicillin correlated to fewer repeat courses. Baseline asthma treatment was not associated with risk of further prescriptions. Antibiotic administration in older patients with a smoking history could be a target for future studies