Class Explorer · Anti-infectives
Cephalosporins
Beta-lactams that bind penicillin-binding proteins and stop cell-wall cross-linking. Generations describe a march from Gram-positive coverage toward Gram-negative and resistance stability.
Members
Also in this class: Cefazolin · Cefuroxime · Ceftazidime · Cefepime. Full pages arrive as the library grows.
Compare the members
- Generation
- First
- Coverage
- Gram-positive, some Gram-negative
- Route
- Oral
- Generation
- Third
- Coverage
- Broad Gram-negative, CSF penetration
- Route
- IV/IM once daily
Shared across the class
- Indications
- Skin and soft tissue infection · Urinary tract infection · Pneumonia · Meningitis (third generation)
- Adverse effects
- Diarrhoea including C. difficile · Rash · Anaphylaxis, rare
- Contraindications
- Prior severe immediate hypersensitivity to a cephalosporin
- Monitoring
- Clinical response by 48 to 72 hours · Renal function for dose adjustment (ceftriaxone is the exception, being largely biliary) · Diarrhoea
What makes each agent different
- First generation (cephalexin, cefazolin) is the Gram-positive workhorse: staphylococci and streptococci, skin and bone.
- Third generation (ceftriaxone) crosses into the CSF and covers Gram-negatives, at the price of collateral damage to gut flora and more C. difficile.
- No cephalosporin covers enterococci, and none of them covers MRSA except ceftaroline. Those two gaps are asked about constantly and forgotten constantly.
The old 10 percent penicillin cross-reactivity figure is wrong by an order of magnitude; modern estimates for later-generation cephalosporins are around 1 to 2 percent and depend on side-chain similarity, not on the beta-lactam ring.
Ceftriaxone and calcium-containing intravenous fluids precipitate in neonates. In adults it is a compatibility issue at the line, not a contraindication.
Last reviewed 2026-08-16 · Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed.