Doxycycline is tetracycline in which the 5beta-hydrogen is replaced by a hydroxy group, while the 6alpha-hydroxy group is replaced by hydrogen. A semi-synthetic tetracycline antibiotic, it is used to inhibit bacterial protein synthesis and treat non-gonococcal urethritis and cervicitis, exacerbations of bronchitis in patients with chronic obstructive pulmonary disease (COPD), and adult periodontitis. It has a role as an antibacterial drug, an antimalarial, a geroprotector, an anti-inflammatory agent and an immunomodulator.