Two different functions of doxycycline which is both an antimicrobial agent and an immune modulator

Doxycycline is a semi-synthetic tetracycline, which was invented and clinically developed in the early 1960s. Doxycycline works by inhibiting protein synthesis and it is also bacteriostatic. Doxycycline is highly effective against all of the common pathogens that cause upper respiratory tract infections. Doxycycline is particularLY effective for the treatment of atypical pneumonia due to Mycoplasma, Chlamydia and Legionella. Recently, doxycycline has been reported to have a biological function apart from its antimicrobial function. Doxycycline is known to inhibit the release of reactive oxygen species, while also inducing apoptosis, decreasing neutrophil chemotaxis and inhibiting matrix metalloproteinases. Regarding animal models, doxycycline is able to attenuate lung inflammation caused by several agents. Recently, several clinical trials using doxycycline have also been reported. In this review, we provide a comprehensive, yet concise analysis of the two different functions of doxycycline, while particularly focusing on respiratory diseases.