Azithromycin hydrate is a macrolide antibiotic useful for the treatment of a number of bacterial infections. In Vitro: Azithromycin (2 μM) augments rhinovirus-induced IFNβ expression in primary bronchial epithelial cells from asthmatics, which is associated with over-expression of RIG-I like receptors and repression of viral replication. Knockdown of MDA5, but not knockdown of RIG-I, diminishes azithromycin (2 μM)-enhanced viral-induced IFNβ expression in asthmatic primary bronchial epithelial cells^[1]. Azithromycin specifically reduces MMP-9 mRNA and protein levels without affecting NF-κB in endotoxin-challenged monocytic THP-1 cells^[2]. In Vivo: Azithromycin (50 mg/kg) has no effect on bronchoalveolar lavage inflammatory parameters and LDH levels in a mouse model of asthma exacerbation. Azithromycin induces neither general inflammatory parameters nor LDH release in a mouse model of asthma exacerbation, and augments expression of interferon-stimulated genes and the pattern recognition receptor MDA5 but not RIG-I in exacerbating mice^[1].