Cephalosporins
Binding penicillin-binding proteins so the bacterial wall is never cross-linked.
Also called cephalosporin antibiotics.
Class card
- Drugs
- Cefalexin, Cefuroxime, Ceftriaxone and Cefixime
- Used for
- Pneumonia
- Bacterial meningitis
- Gonorrhea
- Urinary tract and kidney infections
- Known for
- Allergic reactions, including anaphylaxis
- C. difficile colitis
- Name stems
- cef-
5 cards: the class, and each drug in it.
Mechanism of action
How do cephalosporins work?
Cephalosporins are beta-lactams first derived from Acremonium (Cephalosporium) fungi. Like penicillins, they bind and inactivate penicillin-binding proteins, so peptidoglycan is not cross-linked and the bacterial cell wall weakens and lyses. They withstand many beta-lactamases; from first to third generation, Gram-negative activity rises and Gram-positive activity falls.
The drugs
Cephalosporins with a card
- CefalexinWHO lists it as a first-choice Access antibiotic for skin and soft tissue infections. It does not treat MRSA.
- CefuroximeWHO's essential medicines list places it in the Watch group, as a second choice for surgical prophylaxis.
- CeftriaxoneIt does not cover Chlamydia trachomatis, so chlamydia treatment is added when needed; CDC no longer pairs it with azithromycin for gonorrhea.
- CefiximeWHO classes it as a Watch antibiotic and lists it as a second choice for gonorrhea and acute bacterial dysentery.
Uses
What are cephalosporins used for?
- Pneumonia
- Bacterial meningitis
- Gonorrhea
- Urinary tract and kidney infections
- Skin and soft tissue infections
- Typhoid (enteric fever)
Side effects
Side effects of cephalosporins
- Allergic reactions, including anaphylaxisKnown forSerious
- C. difficile colitisKnown forSerious
- Diarrhea
- Nausea and vomiting
- Rash
- Severe skin reactions (SJS, TEN)Serious
- Immune hemolytic anemiaSerious
- Seizures, mainly when kidney doses are not cutSerious
- Prolonged prothrombin time and bleedingSerious
- Hepatitis and cholestatic jaundiceSerious
What the class has in common. Each drug's card has its own, and Known for marks what an exam expects you to know.
Watch for
Cautions
- Penicillin allergy: up to 1 in 10 people cross-react; avoid them after an immediate-type (anaphylactic) penicillin reaction.
- Kidney impairment: doses are lowered, because cephalosporins that build up can trigger seizures.
- Warfarin, liver disease or poor nutrition: the prothrombin time can rise, so it is checked.
Remember them
A way to remember them
Climb the generations, gain the Gram-negatives: from first to third generation, Gram-negative reach grows while Gram-positive reach shrinks.
First-generation cefalexin suits streptococcal and staphylococcal skin infections. Second-generation cefuroxime adds beta-lactamase-producing H. influenzae. Third-generation ceftriaxone and cefixime reach gonococci, E. coli and Klebsiella, and cefixime misses most staphylococci.
Written for biofideX
Name stems
cef- means cephalosporin
Cefalexin, cefuroxime, ceftriaxone and cefixime share it. Older US names keep the spelling ceph- (cephalexin).
- Every drug name stem
Don't mix them up
Classes easily confused with these
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Cephalosporin Antibiotic (NCI Thesaurus)
- Cephalexin (NCI Thesaurus)
- Cefixime (NCI Thesaurus)
- Cephalexin for oral suspension: label (DailyMed)
- Ceftriaxone for injection: label (DailyMed)
- Cefixime capsules: label (DailyMed)
- WHO Model List of Essential Medicines, 24th list (2025) (WHO)
- Clinical Guidance for Group A Streptococcal Pharyngitis (CDC)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Antibiotics: the cell wall
Practice cephalosporins with the other classes in this group: what each drug is, how it works, what it treats and what it's known for.
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