The effect of antibiotic changes during treatment of cystic fibrosis pulmonary exacerbations.

Background: Antibiotics are often changed during treatment of pulmonary exacerbations (PEx) in people with cystic fibrosis (CF) who have a poor clinical response. We aimed to characterize the reasons CF providers change antibiotics and examined the effects of antibiotic changes on lung function recovery.

Methods: This was a retrospective cohort study using the Toronto CF Database from 2009 to 2015 of adults and children with CF PEx treated with intravenous antibiotics. The co-primary outcome measure was absolute and relative change in forced expiratory lung volume in 1 s (FEV) at end of treatment and follow-up. Secondary outcome assessed the proportion of patients returning to > 90% or > 100% previous baseline FEV.

Results: A total of 399 PEx were included of which 105 had antibiotic changes. Reasons for antibiotic changes included change in antibiotic route prior to discharge (26%), drug reactions (20%), poor FEV response (25%), targeting additional microbes (16%) and lack of symptom improvement (13%). In our multivariable analysis, among non-responders (< 90% FEV recovery to baseline or lack of symptom improvement at the interim time point), a change in antibiotics was not associated with any significant difference in absolute or relative FEV at end of treatment or at follow-up. Antibiotic change in non-responders was not associated with improved return to 90% or 100% baseline FEV at end of treatment or follow-up.

Conclusions: Changing antibiotics during CF PEx treatment in those with poor clinical response was not associated with any improved FEV response or return to baseline lung function.