[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/) › Cefaclor

# Cefaclor

## Beta-lactams?

Beta-lactams

Oral second-generation cephalosporin for otitis, pharyngitis, urinary and skin infections; known for serum sickness-like reactions in children.

Updated Nov 1, 2026

## Quick facts

**Group**
[Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/)

**Target**
Penicillin-binding proteins (bacterial transpeptidases)

**Used for**
Otitis media · Lower respiratory tract infections · S

**Key effects**
Diarrhoea and other gut symptoms · Morbilliform rash

**Monitor**
Rash · INR in people on oral anticoagulants

**ATC**
J01DC04

No doses: the clinician sets them by the current guideline.

On this page

- The basics Mechanism of action
- Indications
- Adverse effects
- Pharmacokinetics
- Memory aid

- Safety Contraindications
- Key interactions
- What is monitored
- Administration and safety
- Pregnancy and breastfeeding
- Nursing care

- Study Test yourself

- Connections Connections

## Mechanism of action

✂**Penicillin-binding proteins (bacterial transpeptidases)**Cefaclor

ⓘ No structure of cefaclor bound to a PBP is published; the figure shows cefalotin, a cephalosporin with the same beta-lactam core, acylating the Streptomyces R61 DD-peptidase, the classic PBP model.

**Target in 3D:** Penicillin-binding proteins (bacterial transpeptidases). PDB structure 1CEG (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1CEG) · Drag to rotate · pinch to zoom

Cefaclor acylates the penicillin-binding proteins and blocks peptidoglycan cross-linking; the wall weakens and the bacterium lyses. Compared with the first generation it gains some activity against H. influenzae and other gram-negatives, but beta-lactamase-negative, ampicillin-resistant H. influenzae is considered resistant.

- Well absorbed by mouth
- Acylates the PBPs of the bacterial wall
- Peptidoglycan cross-linking stops
- The bacterium lyses (bactericidal)

## Indications

- Otitis media [Acute otitis media →](https://durgical.com/en/conditions/acute-otitis-media/)
- Lower respiratory tract infections, including pneumonia [Community-acquired pneumonia →](https://durgical.com/en/conditions/community-acquired-pneumonia/)
- S. pyogenes pharyngitis and tonsillitis (penicillin is usually the first choice) [Streptococcal pharyngitis →](https://durgical.com/en/conditions/streptococcal-pharyngitis/)
- Urinary tract infections, including cystitis and pyelonephritis [Urinary tract infection (acute cystitis) →](https://durgical.com/en/conditions/urinary-tract-infection/)
- Skin and soft-tissue infections

## Adverse effects

### Common

- Diarrhoea and other gut symptoms
- Morbilliform rash, itching and hives
- Eosinophilia
- Genital itching or vaginitis

### Serious (rare, important)

- Serum sickness-like reaction (rash, erythema multiforme, arthritis or joint pain, with or without fever), more frequent in children and with a second course
- Anaphylaxis, Stevens-Johnson syndrome and toxic epidermal necrolysis (rare)
- Pseudomembranous colitis
- Interstitial nephritis, haemolytic anaemia or agranulocytosis (rare)

## Contraindications

- Allergy to cephalosporins

## Key interactions

**Warfarin and other oral anticoagulants**
Increased anticoagulant effect and longer prothrombin time are reported.

**Probenecid**
Reduces its renal excretion.

**Copper-reduction urine glucose tests**
False positives.

## What is monitored

- Rash, joint pain or fever a few days after starting (above all in children)
- INR in people on oral anticoagulants
- Diarrhoea during and after treatment

## Administration and safety

- Capsules and suspension, with or without food
- The extended-release tablet is swallowed whole, close to a meal
- The suspension is shaken and measured with an oral syringe

## Pregnancy and breastfeeding

Animal studies showed no fetal harm and adequate human studies are lacking; it is used only when clearly needed.

## Nursing care

- Ask about penicillin and cephalosporin allergy and about reactions to a previous cefaclor course
- Teach carers to recognise a rash with joint pain
- Warn that it may lower the effect of hormonal contraceptives
- Ask the patient to report watery or bloody diarrhoea

## Pharmacokinetics

**Absorption**
Well absorbed by mouth; food delays and lowers the peak but not the total amount absorbed.

**Elimination**
Renal: 60% to 85% leaves unchanged in the urine within 8 hours.

**Half-life**
Short, 0.6 to 0.9 hours; a little longer in kidney failure.

## Memory aid

«CefaCLOR: CLues on the skin and knees»: a child on a second cefaclor course with hives and sore knees suggests a serum sickness-like reaction.

## Test yourself

Think of the answer, then tap the question to see it.

## A child on a second course of cefaclor develops rash, fever and joint pain a few days in. What reaction is this?

A serum sickness-like reaction, more frequent with cefaclor in children and with repeat courses; it settles when the drug is stopped.

## Which cephalosporin generation does cefaclor belong to?

The second: somewhat more active against H. influenzae and gram-negatives than the first.

## How is cefaclor eliminated, and how long is its half-life?

Mostly unchanged in the urine; its half-life is short, under an hour with normal kidneys.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/cefaclor/)

[More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology)

## Connections

## Related drugs 3

- [Cefuroxime](https://durgical.com/en/pharmacology/cefuroxime/)
- [Cefalexin](https://durgical.com/en/pharmacology/cefalexin/)
- [Amoxicillin](https://durgical.com/en/pharmacology/amoxicillin/)

## Related conditions 4

- [Acute otitis media](https://durgical.com/en/conditions/acute-otitis-media/)
- [Community-acquired pneumonia](https://durgical.com/en/conditions/community-acquired-pneumonia/)
- [Streptococcal pharyngitis](https://durgical.com/en/conditions/streptococcal-pharyngitis/)
- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)

[← Back to the class: Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - CEFACLOR capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=2f61354e-bcb0-41aa-955f-51eabc11387b) (DailyMed (U.S. National Library of Medicine), 2026); [Cefaclor: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682729.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [CEPHALOTHIN COMPLEXED WITH DD-PEPTIDASE](https://www.rcsb.org/structure/1CEG) (RCSB Protein Data Bank, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/cefaclor/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/cefaclor/