Defense Date


Document Type


Degree Name

Doctor of Philosophy


Pharmaceutical Sciences

First Advisor

Patricia W. Slattum


Background: Antibiotic overuse/misuse has been documented in several reports to increase the risk of Clostridioides difficile (C.diff) infection and antibiotic resistance. The older adult population is more prone to use antibiotic medications than any other age group due to decreased immune function, use of urinary catheters, ventilation during hospitalization and other factors. Antibiotic resistance and C.diff are major public health problems. However, studies examining the trends of antibiotic use and the association between the antibiotic use and negative health outcomes among older adults in the outpatient and emergency department settings are limited.

Objectives: The main objectives of this dissertation were to: 1) calculate the national antibiotic trends among community-dwelling older adults in the United State; 2) evaluate the antibiotic trends and antibiotic appropriateness among older adult patients visiting the geriatrics clinic and adult internal ambulatory care clinic at VCU Health; and 3) examine the antibiotic trends and antibiotic appropriateness among older adult patients and middle-aged patients visiting the emergency department at VCU Health.

Methods: For the first objective, data were obtained from Medical Expenditure Panel survey (MEPS) a nationally representative dataset (2011-2015). Descriptive analyses were conducted and multiple logistic regression was performed to assess the association between the antibiotic use and demographic and sociodemographic characteristics. In the second objective, data were obtained from VCU Health outpatient clinics (geriatrics, and Internal medicine ambulatory care clinic only). Descriptive statistics were calculated and multiple logistic regression was performed to assess the association between antibiotic appropriateness and type of clinics and other demographic characteristics. In the third objective, the emergency department electronic medical records at VCU were used. Trend analysis was performed across the dissertation studies using the Cochran–Armitage test. All variables were considered statistically significant at an α level of 0.05. All the statistical analyses were conducted using the Statistical Analysis Software Version 9.4 (SAS v.9.4), (SAS Institute Inc, Cary, NC).

Results: There were 105,762,134 prescriptions dispensed to older adults in the outpatient setting in the US from 2011 to 2015. Antibiotic prescriptions were more common among women (18%) compared to men (12%). White participants received more antibiotics (27%) than African Americans (1.77%) and others (1.4%).

Among the 3,515 patients who visited either Geriatrics or Internal Medicine ambulatory clinic at VCU Health from 2012-2017, 1,534 antibiotics were prescribed. Potentially inappropriate antibiotic prescriptions were similar between the two clinics (30% in Geriatrics clinic and 28% in Internal Medicine ambulatory clinic) with p-value of 0.08.

In addition, 6,343 middle-aged or older adult patients were dispensed and prescribed an antibiotic in the ED at VCU Health from (2012 to 2017). Eighteen percent of the antibiotic prescriptions received by middle age group were considered potentially inappropriate, compared to 9% among the older adult patient (p < 0.0001).

Conclusions: The rate of antibiotic use overall remains unchanged despite the national and international efforts to reduce antibiotic prescriptions and eventually to reduce antibiotic resistance. The changes in the patterns of use in some of the antibiotic categories appear to be driven more by the safety concerns rather than reducing overall use. Future research is needed to strengthen antibiotic stewardship programs for older adults in outpatient settings.


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