Antibiotics in the ER: it's often one-size-fits all

By Marilynn Larkin

NEW YORK (Reuters Health) - Doctors who work in hospital emergency rooms rarely adjust antibiotic doses for obese patients, which can lead to inadequate treatment and fuel antibiotic resistance, according to research reported Tuesday at the American College of Emergency Physicians annual meeting in Boston.

"For certain antibiotics, people who are larger require a larger dose to get and maintain the proper concentration that will reliably kill the bacteria we're trying to get at," study co-researcher Dr. Michael Mullins told Reuters Health.

"But we have a one-size-fits-all dose in our minds for most antibiotics, and we tend to give that dose regardless of size and other factors that should affect dosing, like age, (kidney) function, and body mass index," Mullins said.

"The adjustment isn't all that difficult: in most cases, it means going up to 50 percent more or doubling the dose," he explained. "Otherwise, you might get half or less of the concentration you wanted."

"And if you give too low a dose, you'll have treatment failure even if you pick the right antibiotic -- and increase the likelihood that some of the bacteria you're trying to kill will form a mutation and become less sensitive to the drug," he warned.

Mullins and his colleagues, from Washington University School of Medicine, St. Louis, analyzed the rate at which their center's emergency physicians adhered to dose adjustment guidelines for selected antibiotics established by the university's antibiotic utilization review (AUR) committee.

They reviewed data for a little more than a thousand emergency department patients treated over a 3-month period who weighed more than 100 kilograms (220 pounds), were obese (with a body mass index greater than 40) and were given one of the following antibiotics: cefazolin, cefepime, or ciprofloxacin.

According to the investigators, the antibiotic dosing guidelines in these obese subjects were followed for only 48 doses of cefepime (9.5 percent), 12 doses of cefazolin (4.1 percent), and 4 doses of ciprofloxacin (1.3 percent).

"I think this problem is under recognized by emergency physicians and other specialists," Mullins said. It's particularly troubling, he added, given that "obesity is an epidemic in North America in particular, and unfortunately, we're seeing more people in the obese and severely obese range than we used to."