Cefalexin — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Cefalexin?
Cefalexin is a first-generation cephalosporin antibiotic used for a range of bacterial infections. This medication is funded by Pharmac for skin, urinary, and respiratory infections.
What is Cefalexin Used For?
Cefalexin is used for skin and soft tissue infections (impetigo, cellulitis), urinary tract infections, respiratory tract infections (streptococcal pharyngitis/tonsillitis), ear infections (otitis media), and bone infections.
How Does Cefalexin Work?
Cefalexin is a beta-lactam antibiotic that inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), blocking the transpeptidase cross-linking of peptidoglycan chains. This disrupts cell wall integrity — bactericidal activity against susceptible Gram-positive and some Gram-negative bacteria.
How to Take Cefalexin
Standard dose: 250–500 mg four times daily, or 500 mg twice daily (for urinary tract infections and skin infections). Take with or without food. Complete the full course of treatment even if you feel better. For streptococcal throat infections: 500 mg twice daily for 10 days.
Common Side Effects of Cefalexin
- Nausea, vomiting, diarrhoea
- Stomach upset
- Headache
- Vaginal thrush (candidiasis) in women
- Rash
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Clostridioides difficile colitis (C. diff diarrhoea — report persistent watery or bloody diarrhoea after completing a course)
- Severe allergic reaction and anaphylaxis (rare — 1–2% of penicillin-allergic patients may have cross-reactivity)
- Haemolytic anaemia (rare)
Drug Interactions
Cefalexin may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- Probenecid (increases cefalexin levels)
- Warfarin (possible enhancement of anticoagulant effect)
- Other nephrotoxic agents (additive renal toxicity — rare)
New Zealand Prescribing Information
Cefalexin (250 mg capsules; 500 mg capsules and tablets; 125 mg/5 mL and 250 mg/5 mL suspension) is funded by Pharmac. It is recommended by BPAC NZ as a first-line oral antibiotic for uncomplicated cellulitis and is commonly used for UTIs (particularly in pregnant women, where trimethoprim and nitrofurantoin have restrictions). Cross-reactivity with penicillin allergy is low (approximately 1–2%) in patients with a remote mild reaction — discuss with your doctor if you have a penicillin allergy.
Frequently Asked Questions
If I’m allergic to penicillin, can I take cefalexin?
The cross-reactivity between penicillin and cephalosporins is low (approximately 1–2%), particularly for patients who had a mild non-anaphylactic reaction to penicillin. However, patients with a history of severe anaphylaxis to penicillin should generally avoid cefalexin. Discuss your allergy history with your doctor before taking any cephalosporin.
Do I need to complete the full course of cefalexin?
Yes — stopping antibiotics early when you feel better does not fully eliminate all bacteria and can contribute to incomplete treatment. For streptococcal throat infections, completing the full 10-day course is particularly important to prevent rheumatic fever.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: