Cephalosporins

Key Points

• Cephalosporins are beta-lactam antibiotics that inhibit bacterial cell-wall synthesis similarly to penicillins.
• Organized into generations (first through fifth) with progressively broader gram-negative coverage.
• Cross-sensitivity with penicillins occurs in approximately 1 to 10 percent of penicillin-allergic clients.
• Common prototype agents include cephalexin (first generation) and ceftriaxone (third generation).

Mechanism of Action

Cephalosporins bind to penicillin-binding proteins on bacterial cell walls, inhibiting cell-wall synthesis and causing cell lysis. Like penicillins, they are bactericidal and most effective against actively dividing organisms.

Generational Spectrum

• First generation (cephalexin, cefazolin): Strong gram-positive coverage; used for skin and soft-tissue infections and surgical prophylaxis.
• Second generation (cefuroxime, cefaclor): Expanded gram-negative coverage with retained gram-positive activity.
• Third generation (ceftriaxone, cefotaxime): Broad gram-negative coverage; used for serious infections including meningitis.
• Fourth generation (cefepime): Extended gram-negative and some gram-positive coverage.
• Fifth generation (ceftaroline): Activity against MRSA.

Nursing Considerations

• Assess for penicillin allergy history; cross-sensitivity is possible.
• Monitor for superinfection signs including C. difficile and candidiasis.
• Ceftriaxone should not be mixed with calcium-containing IV solutions in neonates due to precipitation risk.
• Monitor renal function because dose adjustment may be needed in renal impairment.
• Alcohol consumption during and for several days after certain cephalosporins (cefotetan, cefoperazone) may cause a disulfiram-like reaction.

Side Effects and Adverse Effects

• Common: Nausea, vomiting, diarrhea, and GI disturbance.
• Hypersensitivity: Rash, urticaria, and rare anaphylaxis.
• Superinfection: C. difficile colitis risk.
• Hematologic: Rare bleeding tendencies with certain agents.

Health Teaching

• Complete the full prescribed course even if symptoms improve.
• Report diarrhea (especially bloody or persistent), rash, or signs of yeast infection.
• Avoid alcohol with certain cephalosporins to prevent disulfiram-like reaction.
• Take oral forms as directed with regard to food (varies by agent).

Related Concepts

• penicillins - Related beta-lactam class with cross-sensitivity potential.
• antibiotics - Broader antimicrobial therapy framework.
• infection-control - Infection-prevention and antimicrobial stewardship context.

Self-Check

1. How do cephalosporin generations differ in antimicrobial spectrum?
2. Why must allergy history for penicillins be assessed before administering cephalosporins?
3. What is the disulfiram-like reaction associated with certain cephalosporins?