This document classifies cephalosporin antibiotics into five generations based on their chemical structure and properties. First generation cephalosporins such as cephalothin and cefalexin have simple R groups. Second generation drugs like cefaclor and cefuroxime have more complex R groups. Third generation cephalosporins including cefotaxime and ceftriaxone have even more elaborate R groups and broader spectra of activity. Fourth generation cefepime and fifth generation antibiotics like ceftobiprole and ceftaroline have the most intricate R groups and the broadest coverage of bacteria.

1. CLASSIFICATION OF CEPHALOSPORINS
N
H
R
3
N
H
R
1
O
O
S
R
2
O
O
H
Drug R1 R2 R3
First generation
Cephalothin
(Cefalotin) S
O CH3
O
H
Cephaloridine
S N
+
H
Cefalexin NH2 CH3 H
Cefradine NH2 CH3 H
Cefadroxil NH2
O
H
CH3 H
Cefatrizine NH2
O
H
S
N
NH
N
H
Cefazolin N
N
N
N
S N
S
N
H
Second generation
Cefaclor NH2 Cl H
Cefprozil NH2
O
H
CH3
H
Cefamandole
O
O
H
S N
N
N
N
C
H3
H

2. Cefuroxime
N
O
O
CH3
O
O
NH2 H
Cephamycin C O
O
H
NH2
O
O
NH2 OCH3
Cefoxitin S O
O
NH2 OCH3
Cefotetan O
O
H
N
H2
O
S N
N
N
N
OCH3
Cefmetazole S
N
S N
N
N
N
OCH3
Third generation
Cefotaxime
N
S
N
O
CH3
N
H2
O
O
CH3 H
Ceftriaxone
N
S
N
O
CH3
N
H2
S N
N
C
H3
O
O
H
H
Cefixime
N
S
N
H2
O OH CH2 H
Cefoperazine
NH
O
H
N
O
N O
O
CH3
S N
N
N
N
CH3 H

3. Ceftibuten
N
S
N
H2
O OH H H
Ceftazidine
N
S
N
O
N
H2
OH
O
N
+
H
Fourth generation
Cefepime
N
S
N
O
N
H2
CH3
N
+
CH3
H
Cefpirome
N
S
N
O
N
H2
CH3
N
+
H
Cefiderocol
N
S
N
O
N
H2
OH
O
N
+
N
H
Cl
OH
OH
O H
Fifth generation
Ceftobiprole
NH
N
S
N
O
N
H2
N
O
NH
H
Ceftaroline N
O CH3
N
N
S
NH
P
O
O
H
OH
S
N
N
+
CH3
H

4. Ceftozolone
N
N
S
N
O
N
H2
OH
O
N
+
N
C
H3
NH2
NH
NH
O
NH2 H