ATC Code J01DC04
Formula C15H14ClN3O4S
Molar Mass (g·mol−1) 367,81
Physical State solid
CAS Number 53994-73-3
PUB Number 51039
Drugbank ID DB00833
Solubility soluble in hydrochloric acid


Cefaclor belongs to the family of antibiotics known as cephalosporins (cefalosporins). Within this group, it belongs to the second generation. The cephalosporins are broad-spectrum antibiotics used to treat septicemia, pneumonia, meningitis, biliary tract infections, peritonitis, and urinary tract infections.



Cefaclor, like penicillins, is a beta-lactam antibiotic. By binding to specific penicillin-binding proteins (PBPs) located within the bacterial cell wall, it inhibits the third and final stage of bacterial cell wall synthesis. Cell lysis (dissolution of the cell) is then mediated by bacterial cell wall autolytic enzymes such as autolysins.


Cefaclor is well absorbed after oral administration, independent of food intake. Protein binding is 23.5%. There is no significant biotransformation in the liver (approximately 60% to 85% of the drug is excreted unchanged in the urine within 8 hours). The half-life is approximately 0.6-0.9 hours.

Drug Interactions

  • Cephalosporins may potentiate the anticoagulant effect of coumarins (e.g. warfarin) - concomitant use requires frequent INR monitoring and dose adjustment if necessary.
  • Excretion of cephalosporins is decreased by probenecid (resulting in increased concentrations of the drug in blood plasma).
  • Absorption of cefaclor is decreased by antacids. Therefore, antacids should not be taken immediately before or at the same time as cefaclor.


Side effects

The main side effect of cephalosporins is hypersensitivity (drug allergy). Penicillin-sensitive patients also have allergic reactions to the cephalosporins, depending on the cephalosporin generation. Allergic reactions may manifest as e.g. skin rash, pruritus (itching), urticaria, serum sickness-like reactions with skin rash, fever and arthralgia as well as anaphylaxis.

Other side effects include gastrointestinal disturbances (e.g., diarrhea, nausea and vomiting, abdominal discomfort, liver enzyme disturbances, transient hepatitis, and cholestatic jaundice), headache, and Stevens-Johnson syndrome.

Rare adverse reactions include eosinophilia and blood disorders (including thrombocytopenia, leukopenia, agranulocytosis, aplastic anemia, and hemolytic anemia); reversible interstitial nephritis; hyperactivity, nervousness, sleep disturbances, hallucinations, confusion, hypertension, and dizziness.

Symptoms of overdose include diarrhea, nausea, stomach upset, and vomiting.

Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter ist Autor zu pharmazeutischen Themen in der Medizin-Redaktion von Medikamio. Er befindet sich im letzten Semester seines Pharmaziestudiums an der Universität Wien und liebt das wissenschaftliche Arbeiten im Bereich der Naturwissenschaften.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer ist seit 2020 freie Autorin bei Medikamio und studierte Pharmazie an der Universität Wien. Sie arbeitet als Apothekerin in Wien und ihre Leidenschaft sind pflanzliche Arzneimittel und deren Wirkung.

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