The durability of endovascular aneurysm repair (EVAR) has been limited by development of endoleaks which may be secondary to progressive aortic degeneration by matrix metalloproteases (MMP). Doxycycline is a known inhibitor of the MMP family of enzymes in aneurysms. The investigators propose a randomized, controlled trial of adjuvant doxycycline therapy with EVAR to determine its effects on re-intervention, aneurysm shrinkage and serum markers of aneurysmal degeneration.