BACKGROUND Prior studies have found that outpatient antibiotics are commonly prescribed for nonbacterial conditions. It is unclear if national prescribing has changed in recent years given recent public health and antimicrobial stewardship initiatives. This study aimed to describe antibiotic prescribing in United States (U.S.) physician offices. MATERIALS/METHODS This was a cross-sectional study of all sampled patient visits in the Centers for Disease Control and Prevention's National Ambulatory Medical Care Survey from 2009 to 2016. Antibiotic use was defined as at least one oral antibiotic prescription during the visit as identified by Multum code(s). Patient visits were categorized by U.S. geographic region and season. ICD-9-CM and ICD-10 codes were used to assess diagnoses and categorize antibiotic use as appropriate, possibly appropriate, or inappropriate. RESULTS Seven billion visits were included for analysis, with 793,415,182 (11.3%) including an antibiotic. Prescribing rates were relatively stable over the study period (102.9-124.9 prescriptions per 1000 visits); however, 2016 had one of the lowest prescribing rates (107.7 per 1000 visits). The most commonly prescribed antibiotic class was macrolides (25 per 1000 visits). The South region and winter season had the highest antibiotic prescribing (118.2 and 129.7 per 1000 visits, respectively). Of patients who received an antibiotic, 55.9%, 35.7%, and 8.4% were classified as inappropriate, possibly appropriate, and appropriate, respectively. The most common conditions in which antibiotics were prescribed inappropriately included those with no indication in any of the predefined diagnosis codes (40.1%), other skin conditions (17.3%), and viral upper respiratory conditions (13.3%). CONCLUSIONS There was no significant reduction in outpatient antibiotic prescribing rates among U.S. outpatients from 2009 to 2016 and prescribing varied by region and season. These data suggest that more than half of antibiotics were prescribed inappropriately, with the majority of antibiotics prescribed with no indication. However, these findings need to be confirmed with robust prospective studies.

Background Clostridioides difficile infection (CDI) is primarily mediated by alterations in the host gut ecosystem. While antibiotic use is the primary risk factor for CDI, other medications that modulate the gut ecosystem, particularly those targeting the gut-brain axis, could impact CDI risk. This study aimed to investigate the association between recent antidepressant and GABAergic medication use with CDI risk in a national cohort of United States veterans. Methods This was a retrospective case-control study of patients seen in Veterans Health Administration facilities from October 2002 to September 2014. CDI and non-CDI control patients were propensity score matched 1:1 using a maximum caliper of 0.0001. Antidepressant and GABAergic medication use 90 days prior to cohort inclusion were analyzed for CDI association using bivariable and multivariable logistic regression models. Results A total of 85,831 patients were included, and 9,287 CDI and 9,287 control patients were propensity score matched. Antidepressant use overall was not significantly associated with CDI risk (OR 1.05, 95% CI 0.98-1.12), although GABAergic medication use was associated with increased risk (OR 1.81, 95% CI 1.70-1.92). In multivariable models of individual medications/classes, benzodiazepines had the strongest CDI association (OR 1.91, 95% CI 1.77-2.07). SSRIs (OR 0.88, 95% CI 0.81-0.95) and bupropion (OR 0.67, 95% CI 0.57-0.78) were negatively associated with CDI. Conclusion In this national study of veterans, GABAergic medication use was a positive predictor of CDI risk, though antidepressant use was not. Further research is needed to understand biological mechanisms and confirmatory studies are needed to validate these findings.