Cefprozil, an oral cephalosporin antibiotic, is a mixture of antibiotic BMY-28100 (Z- or cis-isomer) and antibiotic BMY-28167 (E- or trans -isomer), the mixture having a Z- to E- isomer ratio in the range of 89:11 to 94:6. BMY-28167 (E- or trans -isomer) is less active when compared with BMY-28100 or isomeric mixture. There were no remarkable differences in the toxicity of the cis isomer, the trans isomer, or cefprozil (the isomeric mixture).

Cefprozil is a 2nd generation cephalosporin that is FDA approved for the treatment of mild to moderate infections of upper respiratory tract, lower respiratory tract, and uncomplicated skin and skin-structure infections. Cefprozil, like the penicillins, is a beta-lactam antibiotic. By binding to specific penicillin-binding proteins (PBPs) located inside the bacterial cell wall, it inhibits the third and last stage of bacterial cell wall synthesis. Common adverse reactions include diarrhea, nausea, vomiting, dizziness, abdominal pain and vaginitis. Nephrotoxicity has been reported following concomitant administration of aminoglycoside antibiotics and cephalosporin antibiotics. Concomitant administration of probenecid doubled the AUC for cefprozil.