SLU Research: Emergency Departments Should Avoid First-Generation Antihistamines in Elderly Patients
After studying the impact of first-generation antihistamines on elderly patients,
Saint Louis University researchers are encouraging doctors to switch to the safer
second-generation antihistamines.
First-generation antihistamines have long been known to cause adverse effects such as confusion in older adults. While routine use of these medications in older adults has been discouraged, the applicability of such recommendations to the emergency department (ED) setting has been controversial, and no prior study has reviewed individual patient charts for adverse effects resulting from just one or two doses given in the ED.
SLU researchers studied adults older than 65 years who received first-generation antihistamines
in an academic ED. In findings recently published, the researchers determined that use of first-generation antihistamines in older
adults, especially those older than 85 years or with prior cognitive impairment, was
associated with infrequent but clinically significant harm.
“This should be a reminder to use second-generation antihistamines whenever possible,
which may require adding a parenteral version to your hospital formulary,” said Cindy
Bitter, M.D., associate professor of surgery at the Saint Louis University School
of Medicine.
Bitter, a co-author of the research, said that first-generation antihistamines, such
as diphenhydramine, are older medications that readily cross into the brain. These
medications are used frequently in the ED for itching, allergic reactions, and as
part of a “headache cocktail.”
The research found that first-generation antihistamines were administered during 3%
of geriatric ED visits. Adverse effects occurred in 15% of these visits, with delirium
and urinary retention being the most common.
Bitter emphasizes that safer alternatives are available for most of these patients.
Second-generation antihistamines generally do not cross into the brain. In the case
of the “headache cocktail,” the antihistamine component may not be necessary at all.
Aligning with new guidelines published by the American Headache Society, Bitter advises that antihistamines should
not be used routinely for the treatment of headache.
In most other instances, Bitter recommends that older adults receive second-generation
antihistamines because they have fewer side effects.
Bitter’s team found a lower risk of adverse drug effects associated with first-generation
antihistamines among geriatric patients than expected, compared to existing data.
However, they noted that the adverse drug effects remained substantial and
disproportionately affected older geriatric patients and those with pre-existing cognitive
impairment.
This study was led by SLU medical students Michael Cusumano and Emily Killen. The
paper was authored by Bitter; Zidong Zhang, Ph.D., MPH, MS, biostatistician at Saint
Louis University’s Advanced HEAlth Data (AHEAD) Institute; Richard Newman, D.O., Graduate
Medical Education; Angela M. Sanford, M.D., interim division director and professor
of geriatric medicine at Saint Louis University; and Jamie Voigtmann, SSM Health Saint
Louis University Hospital Pharmacy.
“Dr. Bitter has really facilitated a number of great research opportunities for medical
students,” Cusumano said. “For this project, she taught us how to do chart review
research by the book. We started by discussing several classic articles on research
methods. We were then able to put the principles into practice with the help of a
fantastic team.”