the macrolide antibiotic azithromycin ( cp-62,993 ; 9-deoxo-9a-methyl-9a-aza-9a-homoerythromycin a ; also designated xz-450 [ pliva pharmaceuticals , zagreb , yugoslavia ] ) showed a significant improvement in potency against gram-negative organisms compared with erythromycin while retaining the classic erythromycin spectrum .
C0052796
azithromycin
C0014806
erythromycin