Azithromycin is a macrolide antibiotic. This broad-spectrum antibiotic of the azalide group is a derivative of erythromycin. Azithromycin is indicated for the treatment of certain types of mild to moderate infections caused by bacteria. Most commonly, it is used to treat ear infections such as otitis media, throat and lung infections such as pharyngitis and pneumonia, and certain skin infections. Azithromycin is also prescribed to patients with cystic fibrosis because they are particularly susceptible to respiratory infections.

A recent study, in the context of the Covid-19 epidemic currently affecting many countries around the world, sought to investigate the effect of azithromycin in combination with hydroxychloroquine. The interest in azithromycin came from the fact that the rate of Covid-19 infection was low in a large cohort of patients with cystic fibrosis, many of whom are on azithromycin therapy.