Azab 500 is a semisynthetic antibiotic, the first representative of the subclass of azalides, somewhat different in structure from classical macrolides.
It is obtained by modifying the 14-membered natural muscle macrolides by incorporating the nitrogen atom into the lactone ring between 9 and 10 carbon atoms, the ring is then converted into a 15-membered ring. This structural reorganization causes a significant increase in acid resistance of the drug – 300 times as compared with erythromycin.