Doxycycline is not effective in reducing the growth of abdom
Abdominal aortic aneurysms affect more than 3% of US older adults. This study aimed to test whether doxycycline reduces the growth of abdominal aortic aneurysm over 2 years as measured by maximum transverse diameter.

Parallel, 2-group, RCT was conducted at 22 US clinical centers and enrolled patients 50 years or older with small (3.5-5.0 cm for men, 3.5-4.5 cm for women) infrarenal aneurysms. Patients were randomized to receive twice daily for 2 years doxycycline 100 mg orally (n=133) or placebo (n=128).

Results: The outcome normal scores used in the primary analysis were based on maximum transverse diameter in 113 patients (88%) in the doxycycline group and 112 patients (90%) in the placebo group; aneurysm repair in 13 (10%) and 9 (7%), and death in 3 (2%) and 4 (3%), respectively. The primary outcome, normal scores reflecting change in aortic diameter, did not differ significantly between the 2 groups, mean change in normal scores, 0.0262 vs 0.0258. Mean baseline maximum transverse diameter was 4.3 cm for doxycycline and 4.3 cm for placebo.

At the 2-year follow-up, the change in measured maximum transverse diameter was 0.36 cm for 96 patients in the doxycycline group vs 0.36 cm for 101 patients in the placebo group. No patients were withdrawn from the study because of adverse effects. Joint pain occurred in 84 of 129 patients with doxycycline and 79 of 125 with placebo.

Conclusively, among patients with small infrarenal abdominal aortic aneurysms, doxycycline compared with placebo did not significantly reduce aneurysm growth at 2 years. These findings do not support the use of doxycycline for reducing the growth of small abdominal aortic aneurysms.