The macrolides are a group of antibiotics whose activity stems from the presence of a macrolide ring and a large lactone ring in their structure. The most commonly-prescribed macrolides are:

erythromycin
clarithromycin
azithromycin

In addition, spiramycin is used for treating toxoplasmosis, and roxithromycin is starting to be recognised as useful for treating cryptosporidium.