cefalexin at a glance
Medicine class
First-generation cephalosporin antibiotic
Available forms
Tablets, capsules and oral liquid
Food
Can be taken with or without food
Common effects
Nausea, diarrhoea and abdominal discomfort
What is cefalexin used for?
Selected products are licensed to treat infections caused by susceptible organisms.
Respiratory tract infections
Urinary tract infections
Skin and soft-tissue infections
Otitis media
Other infections where the causative organism is susceptible to cefalexin
How does cefalexin work?
Cefalexin disrupts construction of the bacterial cell wall while susceptible bacteria are multiplying, causing the cells to break down. It does not treat viral infections.
cefalexin preparations and strengths
Capsule
Route: Oral
Strengths: 500 mg
Oral suspension
Route: Oral
Strengths: 125 mg/5 mL, 250 mg/5 mL
Tablet
Route: Oral
Strengths: 250 mg, 500 mg
How to take cefalexin
Follow the prescription label and your clinician's instructions.
Swallow tablets or capsules whole with water; do not chew or break them.
Cefalexin may be taken with or without food. Taking it after food may help nausea.
Measure liquid with an oral syringe or medicine spoon rather than a kitchen teaspoon.
Check the dispensing label for storage and expiry instructions for reconstituted liquid.
cefalexin side effects
Common or expected effects
- Diarrhoea
- Nausea or vomiting
- Abdominal pain or discomfort
- Indigestion
Get urgent medical advice
- Anaphylaxis, including facial or throat swelling and breathing difficulty
- Severe, persistent or bloody diarrhoea, which may indicate antibiotic-associated colitis
- Blistering, peeling or pustular skin reactions
- Yellow skin or eyes, dark urine or pale stools
- Unexplained bruising or other signs of a blood disorder
cefalexin in pregnancy
Cefalexin can be used during pregnancy when clinically needed. Most pregnancy studies of cephalosporins have not shown harm to the baby, and adequately treating maternal infection is important. Tell the prescriber that you are pregnant.
cefalexin while breastfeeding
Cefalexin is generally compatible with breastfeeding because only small amounts enter milk. Seek advice if the infant feeds poorly or develops vomiting, diarrhoea, oral thrush or a rash. Extra caution may be appropriate for an unwell or premature infant.
cefalexin interactions
Tell the prescriber or pharmacist about all medicines and supplements. Relevant interactions include:
Probenecid
Reduces renal elimination of cefalexin and can increase or prolong cefalexin exposure.
Metformin
Cefalexin may increase metformin exposure, particularly when renal function is impaired.
Oral anticoagulants
Cephalosporins may prolong clotting time, so anticoagulant monitoring may need closer attention.
Common questions about cefalexin
Answers are fully visible for fast scanning and source review.
Is cefalexin a penicillin antibiotic?
No. Cefalexin is a cephalosporin antibiotic, although cephalosporins and penicillins both belong to the beta-lactam family.
Can I take cefalexin if I am allergic to penicillin?
It depends on the type and severity of the previous reaction. Cefalexin must not be taken after a cephalosporin allergy, and severe penicillin allergy requires prescriber assessment because cross-reactions can occur.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.