Medicine & USMLE


Anti-Infective Drugs
  1. Vancomycin
  2. Metronidazole
  3. Penicillins
  4. Cephalosporins
  5. Macrolides
  6. Fluoroquinolones
  7. Aminoglycosides
  8. Tetracyclines
  9. Sulfonamides
  10. Rifampin
  11. Isoniazid
  12. Ethambutol
  13. Chloroquine
  14. Acyclovir
  15. Oseltamivir
  16. Azoles
  17. Nystatin
  18. Amphotericin B


Cephalosporins are a class of antibiotics that are used to treat a wide variety of bacterial infections. Cephalosporins are easy to recognize because they all start with “ceph-”, like ceftriaxone, cefazolin, and cephalexin. Cephalosporins can have a cross sensitivity with penicillins, so if a patient is allergic to one, the severity of the allergic reaction should be determined before giving the other. Patients taking cephalosporins should avoid alcohol to prevent a disulfiram-like reaction. Cephalosporins can cause bleeding so other drugs that cause bleeding should be avoided, like NSAIDs and anticoagulants.

Key Points

  • Cephalosporins
    • Key Drugs
      • Cef-, Ceph-
        • Ceftriaxone (Rocephin)
        • Cefazolin (Ancef)
        • Cephalexin (Keflex)
      • There are 5 different generations of cephalosporins and each generation has coverage for a slightly different spectrum of bacteria
    • Mechanism
      • Beta-lactam Antibiotic
        • Inhibits bacterial cell wall synthesis
    • Clinical Uses
      • Bacterial infections
        • Surgical infection prophylaxis against skin flora
        • Otitis media
        • Meningitis
        • Appendicitis
        • Urinary Tract Infections
        • Respiratory Infections
        • Etc.
    • Side Effects and Adverse Reactions
      • Cross-sensitivity with penicillins
        • The structure and function of cephalosporins is similar to that of penicillins (beta lactam antibiotics) so there can be cross sensitivity
        • Cross-allergenicity rates are relatively low (only about 1-4%)
        • If the patient has a penicillin allergy, the order for cephalosporins should be questioned.
      • Disulfiram-like reaction
        • Do not take with alcohol
      • Bleeding
        • Secondary to vitamin K deficiency, as cephalosporin prevents vitamin K activation which is required for the synthesis of blood clotting factors
        • Thrombocytopenia
        • Avoid drugs that may promote bleeding (e.g. NSAIDS, anticoagulants)
      • Clostridium Difficile overgrowth
        • Broad-spectrum antibiotics like cephalosporins can cause C. difficile overgrowth by killing existing gut flora to open a niche.
        • Cephalosporins cannot treat C. difficile infections
        • Severe diarrhea should be reported, as it may indicate a c. diff. infection
        • Other types of superinfection secondary to antibiotic use include yeast (Candida) infections.
      • GI Distress (nausea, vomiting, diarrhea, anorexia)
        • May be taken with food to reduce GI distress