Cefalexin
⚠️ About 1–6% of penicillin-sensitive patients are also allergic to cephalosporins.
Those with a history of immediate hypersensitivity to penicillin or other β-lactams should not receive cefalexin.
Use with caution in patients with mild sensitivity to β-lactams.
📖 About Cefalexin
- Always check the BNF entry for up-to-date prescribing advice.
- First-generation cephalosporin (β-lactam antibiotic).
- Commonly prescribed in the community for urinary tract, skin, and respiratory infections.
⚙️ Mode of Action
- Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs).
- Bactericidal activity against susceptible Gram-positive and some Gram-negative organisms.
🎯 Indications
- UTIs (esp. in pregnancy where nitrofurantoin unsuitable).
- Respiratory tract infections.
- Otitis media, sinusitis.
- Skin & soft tissue infections (e.g. cellulitis).
💊 Dose Summary
| Indication | Typical Adult Dose | Frequency | Route |
|---|
| General infections | 250–500 mg | Every 8 hours (TDS) | Oral (PO) |
| Severe infections | Up to 1 g | Every 6 hours (QDS) | PO |
| Children | 25–50 mg/kg/day | Divided in 2–4 doses | PO (check BNFc) |
Adjust dose in renal impairment – see BNF.
🔀 Interactions
- See BNF.
- Potential interaction with metformin (risk of lactic acidosis via reduced clearance).
- Enhanced anticoagulant effect with warfarin.
⚠️ Cautions
- History of penicillin allergy (cross-reactivity risk).
- Renal impairment (dose adjustment required).
- Risk of C. difficile infection with broad-spectrum antibiotic use.
🚫 Contraindications
- Immediate hypersensitivity to penicillins or cephalosporins.
💥 Side Effects
- Common: Diarrhoea, nausea, vomiting, abdominal pain, headache, rash.
- Serious: Clostridioides difficile diarrhoea, anaphylaxis, Stevens–Johnson syndrome (rare).
📚 References
