Doxycycline ineffective at shrinking aortic aneurysms in two-year study

Common antibiotic reduces inflammation without changing aneurysm growth

Patients with a vascular condition called abdominal aortic aneurysm did not benefit from taking the common antibiotic doxycycline for two years to shrink the aneurysm when compared to those who took a placebo, according to a Vanderbilt University Medical Center (VUMC) study published in the Journal of the American Medical Association (JAMA).

Abdominal aortic aneurysm is a swelling or ballooning that occurs in the major blood vessel (aorta) that supplies blood from the heart to the lower half of the body. It affects about 3 percent of older Americans, most commonly men and smokers.

The condition can cause fatal internal bleeding if the aneurysm grows large enough to burst. Small aneurysms frequently cause no symptoms and are often detected when an abdominal ultrasound or CT scan is performed for other reasons.

Doctors had traditionally monitored the aneurysm growth and sometimes opt to prescribe doxycycline in an effort to forestall surgery in higher-risk patients, a practice that was based on earlier research suggesting that certain antibiotics reduce inflammation that contributes to aneurysm growth.

The study findings released today could lead doctors to stop prescribing doxycycline as a way to prevent small aneurysms from growing larger and bursting, said John Curci, MD, associate professor of Surgery in the Division of Vascular Surgery at VUMC.

"Taking doxycycline to prevent or slow the growth of small abdominal aortic aneurysms is not advised or helpful, even though it reduced circulating markers of inflammation," said Curci, whose study expertise was bio-banking and bio-specimen analysis with Vanderbilt serving as the Biomarker Core Lab.

The large multicenter NIH/NIA study included 254 patients with small aneurysms who were randomly assigned to take either 100 milligrams of doxycycline twice daily or a placebo for two years.

CT scans performed at the beginning of the study and on follow-up found no differences in aneurysm growth between those who took the drug and those who took the placebo.

"This trial will provide critical material for improved biologic understanding of aneurysm disease," Curci said. "For example, detailed study of the circulating proteins or other markers in blood from these patients might help us better understand why aneurysms grow, and allow us to look for more effective drugs."

The study included 22 clinical sites led by principal investigators from VUMC, University of Maryland School of Medicine, University of Nebraska Medical Center and University of Wisconsin School of Medicine and Public Health.